sample of table of contents in research proposal

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Table of Contents – Types, Formats, Examples

Table of Contents

Definition:

Table of contents (TOC) is a list of the headings or sections in a document or book, arranged in the order in which they appear. It serves as a roadmap or guide to the contents of the document, allowing readers to quickly find specific information they are looking for.

A typical table of contents includes chapter titles, section headings, subheadings, and their corresponding page numbers.

The table of contents is usually located at the beginning of the document or book, after the title page and any front matter, such as a preface or introduction.

Table of Contents in Research

In Research, A Table of Contents (TOC) is a structured list of the main sections or chapters of a research paper , Thesis and Dissertation . It provides readers with an overview of the organization and structure of the document, allowing them to quickly locate specific information and navigate through the document.

Importance of Table of Contents

Here are some reasons why a TOC is important:

• Navigation : It serves as a roadmap that helps readers navigate the document easily. By providing a clear and concise overview of the contents, readers can quickly locate the section they need to read without having to search through the entire document.
• Organization : A well-structured TOC reflects the organization of the document. It helps to organize the content logically and categorize it into easily digestible chunks, which makes it easier for readers to understand and follow.
• Clarity : It can help to clarify the document’s purpose, scope, and structure. It provides an overview of the document’s main topics and subtopics, which can help readers to understand the content’s overall message.
• Efficiency : This can save readers time and effort by allowing them to skip to the section they need to read, rather than having to go through the entire document.
• Professionalism : Including a Table of Contents in a document shows that the author has taken the time and effort to organize the content properly. It adds a level of professionalism and credibility to the document.

Types of Table of Contents

There are different types of table of contents depending on the purpose and structure of the document. Here are some examples:

Simple Table of Contents

This is a basic table of contents that lists the major sections or chapters of a document along with their corresponding page numbers.

Example: Table of Contents

I. Introduction …………………………………………. 1

II. Literature Review ………………………………… 3

III. Methodology ……………………………………… 6

IV. Results …………………………………………….. 9

V. Discussion …………………………………………. 12

VI. Conclusion ……………………………………….. 15

Expanded Table of Contents

This type of table of contents provides more detailed information about the contents of each section or chapter, including subsections and subheadings.

A. Background …………………………………….. 1

B. Problem Statement ………………………….. 2

C. Research Questions ……………………….. 3

II. Literature Review ………………………………… 5

A. Theoretical Framework …………………… 5

B. Previous Research ………………………….. 6

C. Gaps and Limitations ……………………… 8 I

II. Methodology ……………………………………… 11

A. Research Design ……………………………. 11

B. Data Collection …………………………….. 12

C. Data Analysis ……………………………….. 13

IV. Results …………………………………………….. 15

A. Descriptive Statistics ……………………… 15

B. Hypothesis Testing …………………………. 17

V. Discussion …………………………………………. 20

A. Interpretation of Findings ……………… 20

B. Implications for Practice ………………… 22

VI. Conclusion ……………………………………….. 25

A. Summary of Findings ……………………… 25

B. Contributions and Recommendations ….. 27

Graphic Table of Contents

This type of table of contents uses visual aids, such as icons or images, to represent the different sections or chapters of a document.

I. Introduction …………………………………………. [image of a light bulb]

II. Literature Review ………………………………… [image of a book]

III. Methodology ……………………………………… [image of a microscope]

IV. Results …………………………………………….. [image of a graph]

V. Discussion …………………………………………. [image of a conversation bubble]

Alphabetical Table of Contents

This type of table of contents lists the different topics or keywords in alphabetical order, along with their corresponding page numbers.

A. Abstract ……………………………………………… 1

B. Background …………………………………………. 3

C. Conclusion …………………………………………. 10

D. Data Analysis …………………………………….. 8

E. Ethics ……………………………………………….. 6

F. Findings ……………………………………………… 7

G. Introduction ……………………………………….. 1

H. Hypothesis ………………………………………….. 5

I. Literature Review ………………………………… 2

J. Methodology ……………………………………… 4

K. Limitations …………………………………………. 9

L. Results ………………………………………………… 7

M. Discussion …………………………………………. 10

Hierarchical Table of Contents

This type of table of contents displays the different levels of headings and subheadings in a hierarchical order, indicating the relative importance and relationship between the different sections.

    A. Background …………………………………….. 2

      B. Purpose of the Study ……………………….. 3

      A. Theoretical Framework …………………… 5

             1. Concept A ……………………………….. 6

                    a. Definition ………………………….. 6

                     b. Example ……………………………. 7

              2. Concept B ……………………………….. 8

       B. Previous Research ………………………….. 9

III. Methodology ……………………………………… 12

       A. Research Design ……………………………. 12

             1. Sample ……………………………………. 13

               2. Procedure ………………………………. 14

       B. Data Collection …………………………….. 15

            1. Instrumentation ……………………….. 16

            2. Validity and Reliability ………………. 17

       C. Data Analysis ……………………………….. 18

          1. Descriptive Statistics …………………… 19

           2. Inferential Statistics ………………….. 20

IV. Result s …………………………………………….. 22

    A. Overview of Findings ……………………… 22

B. Hypothesis Testing …………………………. 23

V. Discussion …………………………………………. 26

A. Interpretation of Findings ………………… 26

B. Implications for Practice ………………… 28

VI. Conclusion ……………………………………….. 31

A. Summary of Findings ……………………… 31

B. Contributions and Recommendations ….. 33

Table of Contents Format

Here’s an example format for a Table of Contents:

I. Introduction

C. Methodology

II. Background

A. Historical Context

B. Literature Review

III. Methodology

A. Research Design

B. Data Collection

C. Data Analysis

IV. Results

A. Descriptive Statistics

B. Inferential Statistics

C. Qualitative Findings

V. Discussion

A. Interpretation of Results

B. Implications for Practice

C. Limitations and Future Research

VI. Conclusion

A. Summary of Findings

B. Contributions to the Field

C. Final Remarks

VII. References

VIII. Appendices

Note : This is just an example format and can vary depending on the type of document or research paper you are writing.

When to use Table of Contents

A TOC can be particularly useful in the following cases:

• Lengthy documents : If the document is lengthy, with several sections and subsections, a Table of contents can help readers quickly navigate the document and find the relevant information.
• Complex documents: If the document is complex, with multiple topics or themes, a TOC can help readers understand the relationships between the different sections and how they are connected.
• Technical documents: If the document is technical, with a lot of jargon or specialized terminology, This can help readers understand the organization of the document and locate the information they need.
• Legal documents: If the document is a legal document, such as a contract or a legal brief, It helps readers quickly locate specific sections or provisions.

How to Make a Table of Contents

Here are the steps to create a table of contents:

• Organize your document: Before you start making a table of contents, organize your document into sections and subsections. Each section should have a clear and descriptive heading that summarizes the content.
• Add heading styles : Use the heading styles in your word processor to format the headings in your document. The heading styles are usually named Heading 1, Heading 2, Heading 3, and so on. Apply the appropriate heading style to each section heading in your document.
• Insert a table of contents: Once you’ve added headings to your document, you can insert a table of contents. In Microsoft Word, go to the References tab, click on Table of Contents, and choose a style from the list. The table of contents will be inserted into your document.
• Update the table of contents: If you make changes to your document, such as adding or deleting sections, you’ll need to update the table of contents. In Microsoft Word, right-click on the table of contents and select Update Field. Choose whether you want to update the page numbers or the entire table, and click OK.

Purpose of Table of Contents

A table of contents (TOC) serves several purposes, including:

• Marketing : It can be used as a marketing tool to entice readers to read a book or document. By highlighting the most interesting or compelling sections, a TOC can give readers a preview of what’s to come and encourage them to dive deeper into the content.
• Accessibility : A TOC can make a document or book more accessible to people with disabilities, such as those who use screen readers or other assistive technologies. By providing a clear and organized overview of the content, a TOC can help these readers navigate the material more easily.
• Collaboration : This can be used as a collaboration tool to help multiple authors or editors work together on a document or book. By providing a shared framework for organizing the content, a TOC can help ensure that everyone is on the same page and working towards the same goals.
• Reference : It can serve as a reference tool for readers who need to revisit specific sections of a document or book. By providing a clear overview of the content and organization, a TOC can help readers quickly locate the information they need, even if they don’t remember exactly where it was located.

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Researcher, Academic Writer, Web developer

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• Writing Tips

How to Structure the Table of Contents for a Research Paper

4-minute read

• 16th July 2023

So you’ve made it to the important step of writing the table of contents for your paper. Congratulations on making it this far! Whether you’re writing a research paper or a dissertation , the table of contents not only provides the reader with guidance on where to find the sections of your paper, but it also signals that a quality piece of research is to follow. Here, we will provide detailed instructions on how to structure the table of contents for your research paper.

Steps to Create a Table of Contents

• Insert the table of contents after the title page.

Within the structure of your research paper , you should place the table of contents after the title page but before the introduction or the beginning of the content. If your research paper includes an abstract or an acknowledgements section , place the table of contents after it.

• List all the paper’s sections and subsections in chronological order.

Depending on the complexity of your paper, this list will include chapters (first-level headings), chapter sections (second-level headings), and perhaps subsections (third-level headings). If you have a chapter outline , it will come in handy during this step. You should include the bibliography and all appendices in your table of contents. If you have more than a few charts and figures (more often the case in a dissertation than in a research paper), you should add them to a separate list of charts and figures that immediately follows the table of contents. (Check out our FAQs below for additional guidance on items that should not be in your table of contents.)

• Paginate each section.

Label each section and subsection with the page number it begins on. Be sure to do a check after you’ve made your final edits to ensure that you don’t need to update the page numbers.

• Format your table of contents.

The way you format your table of contents will depend on the style guide you use for the rest of your paper. For example, there are table of contents formatting guidelines for Turabian/Chicago and MLA styles, and although the APA recommends checking with your instructor for formatting instructions (always a good rule of thumb), you can also create a table of contents for a research paper that follows APA style .

• Add hyperlinks if you like.

Depending on the word processing software you’re using, you may also be able to hyperlink the sections of your table of contents for easier navigation through your paper. (Instructions for this feature are available for both Microsoft Word and Google Docs .)

To summarize, the following steps will help you create a clear and concise table of contents to guide readers through your research paper:

1. Insert the table of contents after the title page.

2. List all the sections and subsections in chronological order.

3. Paginate each section.

4. Format the table of contents according to your style guide.

5. Add optional hyperlinks.

If you’d like help formatting and proofreading your research paper , check out some of our services. You can even submit a sample for free . Best of luck writing your research paper table of contents!

What is a table of contents?

A table of contents is a listing of each section of a document in chronological order, accompanied by the page number where the section begins. A table of contents gives the reader an overview of the contents of a document, as well as providing guidance on where to find each section.

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What should I include in my table of contents?

If your paper contains any of the following sections, they should be included in your table of contents:

●  Chapters, chapter sections, and subsections

●  Introduction

●  Conclusion

●  Appendices

●  Bibliography

Although recommendations may differ among institutions, you generally should not include the following in your table of contents:

●  Title page

●  Abstract

●  Acknowledgements

●  Forward or preface

If you have several charts, figures, or tables, consider creating a separate list for them that will immediately follow the table of contents. Also, you don’t need to include the table of contents itself in your table of contents.

Is there more than one way to format a table of contents?

Yes! In addition to following any recommendations from your instructor or institution, you should follow the stipulations of your style guide .

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Research Proposal Example/Sample

Detailed Walkthrough + Free Proposal Template

If you’re getting started crafting your research proposal and are looking for a few examples of research proposals , you’ve come to the right place.

In this video, we walk you through two successful (approved) research proposals , one for a Master’s-level project, and one for a PhD-level dissertation. We also start off by unpacking our free research proposal template and discussing the four core sections of a research proposal, so that you have a clear understanding of the basics before diving into the actual proposals.

• Research proposal example/sample – Master’s-level (PDF/Word)
• Research proposal example/sample – PhD-level (PDF/Word)
• Proposal template (Fully editable) 

If you’re working on a research proposal for a dissertation or thesis, you may also find the following useful:

• Research Proposal Bootcamp : Learn how to write a research proposal as efficiently and effectively as possible
• 1:1 Proposal Coaching : Get hands-on help with your research proposal

PS – If you’re working on a dissertation, be sure to also check out our collection of dissertation and thesis examples here .

FAQ: Research Proposal Example

Research proposal example: frequently asked questions, are the sample proposals real.

Yes. The proposals are real and were approved by the respective universities.

Can I copy one of these proposals for my own research?

As we discuss in the video, every research proposal will be slightly different, depending on the university’s unique requirements, as well as the nature of the research itself. Therefore, you’ll need to tailor your research proposal to suit your specific context.

You can learn more about the basics of writing a research proposal here .

How do I get the research proposal template?

You can access our free proposal template here .

Is the proposal template really free?

Yes. There is no cost for the proposal template and you are free to use it as a foundation for your research proposal.

Where can I learn more about proposal writing?

For self-directed learners, our Research Proposal Bootcamp is a great starting point.

For students that want hands-on guidance, our private coaching service is recommended.

Psst… there’s more!

This post is an extract from our bestselling short course, Research Proposal Bootcamp . If you want to work smart, you don't want to miss this .

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Proposal Template AI

Free proposal templates in word, powerpoint, pdf and more

How to Write a Table of Contents in a Proposal Template

A well-organized proposal is crucial for conveying a professional and structured approach to potential clients or stakeholders. One essential element of a proposal is the table of contents, which provides an overview of the document’s structure and key sections.

What is a Table of Contents in a Proposal?

The table of contents is a list of the main sections and subsections of the proposal, along with their page numbers. It serves as a roadmap for the reader, making it easy for them to navigate the document and locate specific information quickly.

How to Write a Table of Contents

Understand the Proposal Structure : Before creating the table of contents, familiarize yourself with the overall structure of the proposal. Identify the main sections and subsections that will be included.

Use Heading Levels: Utilize heading levels to denote the hierarchy of sections and subsections. For example, the main sections can be designated as Heading 1, while subsections can be Heading 2 or Heading 3.

Insert Page Numbers: Once the proposal is complete, insert page numbers for each section and subsection. This will ensure that the table of contents accurately reflects the document’s layout.

Create the Table of Contents: In your word processing software, use the automatic table of contents feature to generate the list based on the headings and page numbers you have designated.

What type of proposal templates is the table of contents used in?

The table of contents is a standard element in various types of proposal templates , including business proposals , project proposals, research proposals , and grant proposals .

Can I customize the table of contents format?

Yes, you can customize the appearance of the table of contents to match the overall design of your proposal. Most word processing software allows for customization of font, spacing, and formatting.

Advice for the End User

• Check the table of contents after making any revisions to the proposal to ensure that it accurately reflects the document’s content and structure.
• Keep the table of contents concise and organized, as it serves as a snapshot of the proposal’s key sections.
• Utilize the table of contents as a tool for presenting a clear and logical flow of information to the reader.

By following these guidelines, you can create a well-crafted table of contents for your proposal template, improving the document’s overall readability and professional presentation.

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Table of Contents for Thesis Proposal

The table of contents for thesis proposal on the page that is dedicated to the chapters and their respective page numbers. The headings and subheadings are also mentioned on the page. The formatting for this page should be consistent and clear.

The table of contents is added after the introduction page and before the abstract. The table of contents should be of two pages, not more than that.

If you are planning on writing your thesis, do not skip this page and read further for the format and pattern of the table of contents.

In this post, you will learn:

What should you include in the table of contents?

Appendices and tables, the do’s and don’t’s, examples of the table of contents, a checklist for the table of contents.

Now that we have covered what the table of content is, you need to know what is included within the two pages of the list. If you feel like any portion of your dissertation is troubling you, you should get   dissertation writing help   by all means.

The table of content is an organized list that provides basic knowledge of what your thesis contains. The names of the chapters along with subheadings are added on the left side of the page. Whereas the number of the pages is written on the right side.

The table of contents is created for the sole purpose of locating a chapter and subheading by the reader. One should check with their universities and colleges if they have a specific format for the table of content.

Let us look into the general format of a table of content. The chapters (first level) and their second-level headings should be added to this. Remember, your motive behind creating this page is to make it easy for the reader to locate your chapters.

For example: Level one heading – Chapter 2. Literature Review Level two heading -2.1 Research Gap

The table of contents must include your appendices and table of figures. If you have more than three and four figures and tables, then they deserve their chapter. But if you dint get a lot of results from research, then those tables and figures can be shared in the list of contents.

Now the question arises, what does the appendices chapter include?

• The original interviews, surveys, and questionnaires that were used to collect data for the research
• Not more than two figures and tables should be added to the table of content.
• If did not use a lot of abbreviations then you should share them in the table of content. But if you have tons of abbreviations and technical terms, then they should be listed in their chapters.

What are the Do’s and Don’t’s of the table of contents

The table of content may seem like a simple two-page table but in actuality can badly affect your thesis if not composed correctly. Due to this reason, one should be extra careful while numbering the pages and creating the different level headings.

Example of the table of contents

The page numbers assigned to the chapters in the table of contents should be the same as the number assigned at the beginning of each chapter. The example below demonstrates just that:

Checklist for the table of contents

To achieve perfection in the list of contents, you need a set of rules to follow. A starter’s checklist will guide you to do just that. Below is a checklist that will make sure your table of content is up to mark. And no matter what academic level of thesis you compose, this checklist can be used for all of them:

Collect the relevant information about the format according to your university and referencing style.

Start with the list of tables and bold the main chapters., all the titles of the chapter should be level one heading and the subheading should be level two., the numbers of the chapters and the page numbers given in the table should tally., all pages should be numbered after the chapters are written., final words:.

To create the table of contents for your thesis, use Microsoft word and customized it according to your thesis requirement. Apply the headings according to your style of preference. You can easily make the changes to the table itself at point of time with the help of the Microsoft Word table of contents.

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Table of Contents

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A guide to the table of contents page

Inhaltsverzeichnis

• 1 Definition: Table of Contents
• 3 Everything for Your Thesis
• 5 Create in Microsoft Word
• 6 In a Nutshell

Definition: Table of Contents

The table of contents is an organized listing of your document’s chapters, sections and, often, figures, clearly labelled by page number. Readers should be able to look at your table of contents page and understand immediately how your paper is organized, enabling them to skip to any relevant section or sub-section. The table of contents should list all front matter, main content and back matter, including the headings and page numbers of all chapters and the bibliography . A good table of contents should be easy to read, accurately formatted and completed last so that it is 100% accurate. Although you can complete a table of contents manually, many word processing tools like Microsoft Word enable you to format your table of contents automatically.

When adding the finishing touches to your dissertation, the table of contents is one of the most crucial elements. It helps the reader navigate (like a map) through your argument and topic points. Adding a table of contents is simple and it can be inserted easily after you have finished writing your paper. In this guide, we look at the do’s and don’ts of a table of contents; this will help you process and format your dissertation in a professional way.

When adding the finishing touches to your dissertation, the table of contents is one of the most crucial elements. It helps the reader navigate (like a map) through your argument and topic points. Adding a table of contents is simple and can be inserted easily after you have finished writing your paper. In this guide, we look at the do’s and don’ts of a table of contents; this will help you process and format your dissertation in a professional way.

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What is a table of contents?

A table of contents is a list, usually on a page at the beginning of a piece of academic writing , which outlines the chapters or sections names with their corresponding page numbers. In addition to chapter names, it includes bullet points of the sub-chapter headings or subsection headings. It usually comes right after the title page of a research paper.

How do you write a table of contents

To write a table of contents, you first write the title or chapter names of your research paper in chronological order. Secondly, you write the subheadings or subtitles, if you have them in your paper. After that, you write the page numbers for the corresponding headings and subheadings. You can also very easily set up a table of contents in Microsoft Word.

Where do you put a table of contents?

The table of contents is found on a page right at the beginning of an academic writing project. It comes specifically after the title page and acknowledgements, but before the introductory page of a writing project. This position at the beginning of an academic piece of writing is universal for all academic projects.

What to include in a table of contents?

A sample table of contents includes the title of the paper at the very top, followed by the chapter names and subtitles in chronological order. At the end of each line, is the page number of the corresponding headings. Examples of chapter names can be: executive summary,  introduction, project description, marketing plan, summary and conclusion. The abstract and acknowledgments are usually not included in the table of contents, however this could depend on the formatting that is required by your institution. Scroll down to see some examples.

How important is a table of contents?

A table of contents is very important at the beginning of a writing project for two important reasons. Firstly, it helps the reader easily locate contents of particular topics itemized as chapters or subtitles. Secondly, it helps the writer arrange their work and organize their thoughts so that important sections of an academic project are not left out. This has the extra effect of helping to manage the reader’s expectation of any academic essay or thesis right from the beginning.

Everything for Your Thesis

A table of contents is a crucial component of an academic thesis. Whether you’re completing a Bachelor’s or a postgraduate degree, the table of contents is a requirement for dissertation submissions. As a rule of thumb, your table of contents will usually come after your title page , abstract, acknowledgement or preface. Although it’s not necessary to include a reference to this front matter in your table of contents, different universities have different policies and guidelines.

Although the table of contents is best completed after you have finished your thesis, it’s a good idea to draw up a mock table of contents in the early stages of writing. This allows you to formulate a structure and think through your topic and how you are going to research, answer and make your argument. Think of this as a form of “reverse engineering”. Knowing how your chapters are going to be ordered and what topics or research questions are included in each will help immensely when it comes to your writing.

The table of contents is not just an academic formality, it allows your examiner to quickly get a feel for your topic and understand how your dissertation will be presented. An unclear or sloppy table of contents may even have an adverse effect on your grade because the dissertation is difficult to follow.

Examiners are readers, after all, and a dissertation is an exercise in producing an argument. A clear table of contents will give both a good impression and provide an accurate roadmap to make the examiner’s job easier and your argument more persuasive.

Your table of contents section will come after your acknowledgements and before your introduction. It includes a list of all your headers and their respective pages and will also contain a sub-section listing your tables, figures or illustrations (if you are using them). In general, your thesis can be ordered like this:

1. Title Page 2. Copyright / Statement of Originality 3. Abstract 4. Acknowledgement, Dedication and Preface (optional) 5. Table of Contents 6. List of Figures/Tables/Illustrations 7. Chapters 8. Appendices 9. Endnotes (depending on your formatting) 10. Bibliography / References

The formatting of your table of contents will depend on your academic field and thesis length. Some disciplines, like the sciences, have a methodical structure which includes recommended subheadings on methodology, data results, discussion and conclusion. Humanities subjects, on the other hand, are far more varied. Whichever discipline you are working in, you need to create an organized list of all chapters in their order of appearance, with chapter subheadings clearly labelled.

Sample table of contents for a short dissertation:

Abstract ………………………………………………………………………………………………….. ii Acknowledgements ………………………………………………………………………………………………….. iii Dedication ………………………………………………………………………………………………….. iv List of Tables ………………………………………………………………………………………………….. x List of Figures ………………………………………………………………………………………………….. xi Chapter 1: Introduction ………………………………………………………………………………………………….. 1 Chapter 2: Literature Survey ………………………………………………………………………………………………….. 13 Chapter 3: Methodology ………………………………………………………………………………………………….. 42 Chapter 4: Analysis ………………………………………………………………………………………………….. 100 Chapter 5: Conclusion ………………………………………………………………………………………………….. 129 Appendices ………………………………………………………………………………………………….. 169 References ………………………………………………………………………………………………….. 172

When producing a more significant and longer dissertation, say for a Master’s degree or even a PhD, your chapter descriptions should contain all subheadings. These are listed with the chapter number, followed by a decimal point and the subheading number.

Sample table of contents for a PhD dissertation:

Chapter 1 1.1 Introduction 1.2 Literature Review 1.3 Data 1.4 Findings 1.5 Conclusion

Chapter 2, and so on.

The key to writing a good table of contents is consistency and accuracy. You cannot list subheadings for one chapter and forget them for another. Subheadings are not always required but they can be very helpful if you are dealing with a detailed topic. The page numbers in the table of contents must match with the respective pages in your thesis or manuscript.

What’s more, chapter titles and subheading titles must match their corresponding pages. If your first chapter is called “Chapter 1: The Beginning”, it must be written as such on both the table of contents and first chapter page. So long as you remain both accurate and consistent, your table of contents will be perfect.

Create in Microsoft Word

Fortunately, the days of manually writing a contents page are over. You can still produce a contents page manually with Microsoft Word, but consider using their automatic feature to guarantee accuracy and save time.

To produce an automatically-generated table of contents, you must first work with heading styles. These can be found in the home tab under “Styles”. Select top-level headings (your chapter titles) and apply the Heading 1 style. This ensures that they will be formatted as main headings. Second-level headings (subheadings) can be applied with the Heading 2 style. This will place them underneath and within each main heading.

Once you have worked with heading styles, simply click on the “References” tab and select “Table of Contents”. This option will allow you to automatically produce a page with accurate page links to your document. To customize the format and style applied to your table of contents, select “Custom Table of Contents” at the bottom of the tab. Remember to update your table of contents by selecting the table and choosing “Update” from the drop-down menu. This will ensure that your headings, sub-headings and page numbers all add up.

Thesis Printing & Binding

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In a Nutshell

• The table of contents is a vital part of any academic thesis or extensive paper.
• It is an accurate map of your manuscript’s content – its headings, sub-headings and page numbers.
• It shows how you have divided your thesis into more manageable chunks through the use of chapters.
• By breaking apart your thesis into discrete sections, you make your argument both more persuasive and easier to follow.
• What’s more, your contents page should produce an accurate map of your thesis’ references, bibliography, illustrations and figures.
• It is an accurate map of the chapters, references, bibliography, illustrations and figures in your thesis.

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Publishing and the Mentoring Network Journal

ARTICLE 6: The Layout and Structure of a Table of Contents for a Ph. D. Research Proposal

Written by Dr J.P. Nel

Introduction

The table of contents is your first opportunity to impress upon the Postgraduate Committee and your study leader the importance and value of your planned research.

Especially experienced professors often claim that they can already see if your study proposal is viable or not by just looking at the table of contents.

Just to avoid confusion – you can have two tables of content in your research proposal. The first would be the table of contents for the proposal itself and the second can be the proposed table of contents for your research report.

In this post, I will share with you hints on what you should write under each heading of your table of content to gain the approval of the Postgraduate Committee and your study leader.

The table of contents

To begin with, here is an example of a table of contents for a research proposal.

Table of Contents

                                                                                                Page no

1      Introduction                                                                          1

1.1  Introduction to the problem                                                 1

1.2  The Primary Focus of the Study                                           2

1.3  The Importance of the Problem                                            2

1.4  Definition of the Problem                                                       3

1.5  Definition of Concepts                                                           3

1.6  The Motivation for the Study                                                 5

1.7  Current Knowledge of the Problem                                      5

1.8  Potential Benefits of the Research                                       6

2     Research Design                                                                 7

2.1  The Research Approach                                                       7

2.2  Research Methodology                                                         8

2.3  Data-collection Strategy                                                         9

2.4  Ethical Issues for Consideration                                           10

2.5  Proposed Chapter-outline and Deadline Dates                  11

3     References                                                                            12

4     Definitions                                                                             13

5     Quick Reference Manual                                                    14       

You will notice that the research proposal consists of three main sections, namely the introduction, the body and supplementary information.

In the introduction, you should discuss the context and purpose of your planned research.

In the body, you should discuss how you will approach and conduct the research.

Supplementary information should lend authenticity and validity to your proposal.

1      Introduction                                                                         

1.1  Introduction to the problem

See if you can here already impress upon the Postgraduate Committee the importance of the study by discussing your ideas in the context of your planned target group or target area.

You should link your introduction to the environmental factors that you regard as wonting and show how your research can solve problems in that context.

Do not criticize if you do not have facts to substantiate your claims.

1.2  The Primary Focus of the Study

Keep in mind that your research proposal, like your eventual research report, should follow the so-called golden thread that runs through your study.

To achieve this, let the environment and context that you discussed in the introduction to the problem develop into your focus for the study.

After all, you should focus on the research problem if you are to solve it.

1.3  The Importance of the Problem

Link the importance of the problem with the previous issue, that is the focus of your study. Discuss why the problem is important and who will benefit if the problem is solved.

Do not claim over-emotional problems. Always reason in an objective and professional manner.

It is especially when you choose a critical paradigm, for example, critical theory, critical race theory, or feminism that researches sometimes can ignore the facts to prove a point about which they feel strongly.

1.4  Definition of the Problem

Please do not now define a problem that has no relevance to what you discussed so far. Your problem statement, problem question or hypothesis should follow from what you already wrote.

The research approach that you will follow will largely decide if you will define a research problem, research question or hypothesis.

You will probably formulate a hypothesis if you intend to use quantitative research.

You will probably formulate a research problem or research question if you intend to use a qualitative approach.

You can have more than one research problem or question, but don’t list too many. I would suggest not more than three.

1.5  Definition of Concepts

The definition of concepts is a challenge even in the policies and procedures for Ph.D. and master’s degree studies of universities and other research organisations.

That is why you will need to explain what you mean by key terms and concepts.

Once you have explained what you mean by such terms and concepts, you must apply the meanings consistently.

1.6  The Motivation for the Study

The motivation for the study links up with the importance of the study. The importance of the study is mostly also the motivation for the study.

You should not use something like “It is important because my dad wants me to study for a Ph.D.” as a motivation for the study.

Your motivation for the study should reflect the needs of the community, a sponsor, the academic fraternity, even perhaps the entire world.

The potential value of your study should invite acceptance, validity and sincerity.

1.7  Current Knowledge of the Problem

It would be risky to choose a research topic about which you know nothing.

You will probably need to do some prior studying and you should provide evidence of such prior knowledge and, perhaps, experience.

You can also mention the profiles of the individuals or organisations who will be involved in your research if it is relevant.

Just keep in mind that they cannot do your research for you.

1.8  Potential Benefits of the Research

Your research must have theoretical value, practical value and scientific value.

Theoretical value would be the new knowledge that will result from your research.

Practical value would be what can be applied in the industry.

Scientific value can be to the benefit of a field of science.

Theoretical, practical and scientific value can form the basis for future research.

2     Research Design                                                                

2.1  The Research Approach

You should mention if you will do quantitative or qualitative research.

Briefly explain why you chose the approach that you did.

You can also discuss the paradigmatic approach that you will follow here, or you can discuss it under a separate heading, also here.

2.2  Research Methodology

Make sure that the research methodology that you will use is reconcilable with the research approach that you chose.

2.3  Data-collection Strategy

Data collection strategies are often regarded as research methods.

I don’t think this is a serious problem because data collection strategies are, indeed, often also research methods.

Then again, not all data collection strategies go with all research methods or even research approaches.

This, however, is also not a serious problem.

You will learn that what you intended to do cannot be done once you get to the point where you need to do the research and collect the data.

2.4  Ethical Issues for Consideration

We will discuss ethical issues in much more detail in a future post because ethics in Ph.D. are a mouthful. It includes issues such as being honest, protecting the identity of people involved in your research, not committing plagiarism, trust, deception, legality, professionalism and many more.

2.5  Proposed Chapter-outline and Deadline Dates

The proposed chapter outline can be a provisional table of contents for your research report.

You will also need to provide deadline dates for your research.

We will discuss the chapter-outline and deadline dates separately in future posts.

3     References

You can have a separate heading for literature study in which you list the references that you already consulted and a list of references for your research proposal.

Don’t list references that you did not use. If you list references that you did not use yet in your literature study, you will need to point this out.

4     Definitions and a Quick Reference Manual

You might have separate headings for references and a quick reference manual.

Not all study leaders will allow this, though.

Definitions and the quick reference manual are mostly there to help you maintain consistency in your writing.

Summary and close

In summary:

• If your research proposal does not show that your research topic is important and that you can do the research, the Postgraduate Committee will probably not approve your application.
• Keep your research proposal sufficiently simple for you to understand everything that you write.
• Make sure that you know what the university will require you to cover in your research proposal.

You may also like

Article 29: research methods for ph. d. and masters degree studies: field research, article 96: research methods for ph. d. and master’s degree studies: methods for organising and analysing data: part 2 of 2 parts, article 21: consulting sources of information for your ph. d. or masters degree research., leave a reply cancel reply.

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The Graduate School

University information technology (uit), main navigation, formatting requirements: preliminary pages.

• Submission Procedure
• Policies for Theses and Dissertations
• Coauthored Theses and Dissertations
• Approval Requirements
• Publication Requirements

Copyright Page

Statement of thesis/dissertation approval, dedication, frontispiece, and epigraph, table of contents and list of figures/tables, acknowledgements.

• General Formatting Requirements
• Parts Composed of Related Chapters
• Headings and Subheadings
• Tables and Figures
• Footnote and Reference Citations
• Appendix or Appendices
• References or Selected Bibliography
• Documentation Styles
• Writing Styles
• Print Quality
• Accessibility in the PDF
• Electronic Version Submitted for Thesis Release
• Distribution of Theses and Dissertations
• Alternate Text
• Color Contrast
• Accessibility Issues in Table Construction
• Heading Space
• Double Space
• Single Space
• Previously Published, Accepted, and Submitted Articles as Chapters of a Dissertation
• Alternate Figure/Table Placement

Preliminary pages are, in order, the title page; copyright page; statement of thesis/dissertation approval; abstract; dedication (optional); frontispiece (optional); epigraph (optional); table of contents; lists of tables, figures, symbols, and abbreviations (necessary only in certain situations); and acknowledgments (optional). Table 2.1 lists all the possible preliminary sections in order and if they are required or not. 

The preliminary pages are counted in sequence (except the copyright page, which is neither counted nor numbered). Any page with a main heading on it (title page, abstract, table of contents, etc.) is counted, but no page number is typed on the page. Second pages to the abstract, table of contents, lists, and acknowledgments are numbered with lower case Roman numerals centered within the thesis margins and .5” from the bottom of the page. See the preliminary pages in this handbook for an example. 

Order of preliminary pages, indicating which are mandatory and where page numbers should be included.

Note : Page numbers in the preliminary pages appear centered on the bottom of the page in lower case Roman numerals. This differs from page numbers in the text, which appear on the top right of the page and use Arabic numerals.

SEE Sample Preliminary Pages

The title page is page i (Roman numeral) of the manuscript (page number not shown). 

The title of the thesis or dissertation is typed in all capital letters. The title should be placed in the same size and style of font as that used for major headings throughout the manuscript. If longer than 4 1/2 inches, the title should be double spaced and arranged so that it appears balanced on the page. The title should be a concise yet comprehensive description of the contents for cataloging and data retrieval purposes. Initials, abbreviations, acronyms, numerals, formulas, super/subscripts, and symbols should be used in the title with careful consideration of clarity and maximizing search results for future readers. Consult the manuscript editors if in doubt. 

The word “by” follows the title. The full legal name of the author as it appears in CIS follows after a double space. The name is not typed in all capital letters. These two lines of text are centered between the title and the statement described in the following paragraph. 

The statement “A thesis submitted to the faculty of The University of Utah in partial fulfillment of the requirements for the degree of” appears single spaced in the middle of the title page (see Figure 2.1). For doctoral candidates, the phrasing reads “A dissertation submitted. . . ” 

The appropriate degree follows the statement. The space between the statement and the degree should be the same size that is between the author’s name and the statement. In the event the name of the degree differs from the name of the department, e.g., Master of Science in Environmental Humanities, the words “Master of Science” are placed below the statement, followed by “in” and then the degree program; the lines of the degree name and program are double spaced (see Figure 2.2). Thus, a student receiving a doctorate in history need use only the words “Doctor of Philosophy.” A student receiving a doctorate in Geophysics must put “Doctor of Philosophy in Geophysics.” 

Below the degree field, the full name of the department is listed on the title page. “The University of Utah,” is listed a double space below the department name.

The date appears on the title page a double space below “The University of Utah.” Only the month and year appear, with no punctuation separating them. The month indicates the last month in the semester the degree is granted: fall semester, December; spring semester, May; summer semester, August. 

Again, the spaces below the title, the full legal name, the statement, and the degree should be of equal size. 

The second page is the copyright page, which is uncounted and unnumbered. A copyright notice appears in every copy of the thesis or dissertation. The notice, as illustrated in Figure 2.3, is centered within the side margins and the top and bottom margins of the page. 

Copyright © Student’s Full Legal Name 2022

All Rights Reserved 

There is a double space between the two lines. 

The statement of thesis/dissertation approval is page ii (Roman numeral) of the manuscript (page number not shown). This statement is prepared as shown in Figures 2.4 (for master’s students) and 2.5 (for doctoral students). 

The statement of thesis/dissertation approval signifies that the thesis or dissertation has been approved by the committee chair and a majority of the members of the committee and by the department chair and the dean of The Graduate School. The names of any committee members who did not approve or digitally sign the forms for the thesis or dissertation are not dated. The dates entered should match the date when you received notification that the committee member electronically signed the form. 

The full name of the student, as it appears on the title page and copyright page, must be used. 

As with the digital signature forms, full legal names of committee members must be listed. The full legal names of committee members and department chair or dean can be found on your CIS page under the Committee tab. Neither degrees nor titles should be listed with the names of faculty members. No signatures are required. 

Abstract Page

The abstract is page iii, unnumbered; if there is a second page, it is page iv, and a number appears on the page. The abstract is a concise, carefully composed summary of the contents of the thesis or dissertation. In the abstract, the author defines the problem, describes the research method or design, and reports the results and conclusions. No diagrams, illustrations, subheadings, or citations appear in the abstract. The abstract is limited to 350 words (approximately 1.5 double-spaced pages). A copy of the abstract of all doctoral candidates is published in Dissertation Abstracts International. The word ABSTRACT is placed 2 inches from the top of the page in all capital letters. Following a heading space, the abstract text begins, with the first line indented the same size space as for the paragraphs in the remainder of the manuscript. The text of the abstract must be double spaced. 

If a manuscript is written in a foreign language, the abstract is in the same language, but an English version (or translation) of the abstract must precede the foreign language abstract. The two abstracts are listed as one in the table of contents. The first page of each version is unnumbered but counted. If there is a second page to each version of the abstract, the page number (lower-case Roman numeral) is centered between the left and right margins and between the bottom of the page and the top of the bottom margin. 

The dedication is an optional entry; enumeration continues in sequence, but no page number appears on the page. It follows the abstract and precedes the table of contents. Often only one or two lines, it is centered within the top and bottom margins of the page and within the thesis margins. It is not labeled “Dedication” and is not listed in the table of contents. 

Frontispiece and Epigraph

These are infrequently used entries. The frontispiece is an illustration that alerts the reader to the major theme of the thesis or dissertation. An epigraph is a quotation of unusual aptness and relevance. 

Contents or Table of Contents

The table of contents follows the abstract (or dedication if one is used). The word CONTENTS (or TABLE OF CONTENTS) is placed 2 inches from the top of the page in all capital letters. Following a heading space, the table of contents begins. The table of contents, essentially an outline of the manuscript, lists the preliminary pages beginning with the abstract (page iii). It does not list a frontispiece, dedication, or epigraph if these are used, nor is the table of contents listed in the table of contents; these pages are, however, counted. The list of figures and list of tables, if used, are included (see the Table of Contents in this handbook for a sample using numbered chapters; see Figures 2.6, 2.7, and 2.8 for additional options). 

All chapters or main sections and all first-level subheadings of the manuscript are listed in the table of contents. No lower subheadings levels are to appear in the table of contents. Beginning page numbers of each chapter or section listed are lined up with each listing by a row of evenly spaced, aligned period leaders. The numbers, titles, and subheadings of chapters or sections used in the table of contents must agree exactly in wording and capitalization with the way they appear on the actual page. 

The table of contents reflects the relationship of the chapters and subheadings. Chapter titles appear in all capital letters, as do titles of appendices. First-level subheadings can be headline style or sentence style in capitalization. Subheadings are neither underlined nor italicized in the table of contents. If the table of contents continues to a second page, it begins 1 inch from the top of the page, and it is not labeled “Table of Contents Continued.” Main headings are followed by a double space in the table of contents; all subheadings are single spaced. The words “Chapters” and “Appendices” are used as referents only, printed above the list of entries. The word “Chapter” or “Appendix” is not repeated with each entry. 

List of Figures / List of Tables

The enumeration continues in sequence; no number appears on pages with main headings (those in all caps). A list of tables, a list of figures, a list of symbols, a list of abbreviations, or a glossary may be used. All lists follow the table of contents. The title is placed 2 inches from the top edge of the page in all capital letters: LIST OF TABLES. Following a heading space, the list begins. A list of tables or a list of figures is required if there are 5 to 25 entries. Lists with fewer than 5 entries or more than 25 are not included. It is not permissible to combine a list of tables and figures. The word “Table” or “Figure” is not repeated with each entry. 

As noted for entries in the table of contents, the listing of tables and figures must agree exactly in wording, capitalization, and punctuation with the table title or figure caption. (An exception to this rule occurs if the table title appears in all capital letters on the table itself; table titles in the list of tables are not typed in all capital letters.) Capitalization styles may not be mixed. In the case of long titles or captions, the first sentence must convey the essential description of the item. The first sentence alone then is used in the list. Long captions may not be summarized. 

The table or figure number begins at the left margin and is followed by the title or caption. The page on which each table or figure appears is at the right margin. As in the table of contents, the page numbers are lined up with each entry by a row of evenly spaced, aligned periods (period leaders). If a table or figure occupies more than one page, only the initial page number is listed. If the title or caption of a table or figure appears on a part-title page preceding the table or figure, the page number in the list refers to the number of the part-title page. 

If a list continues to a second page, the second page of text begins 1 inch from the top of the page. The second page is not labeled “List of Tables Continued” or “List of Figures Continued.” Individual entries are single-spaced with a double space between each entry. 

A list of symbols and abbreviations or a glossary does not replace defining terms, symbols, or abbreviations upon their first occurrence in the text. When introducing terms, always introduce terms upon their first usage in the document. 

The enumeration continues in sequence; no number appears on the first page. Acknowledgments are optional. If a preface is used, the acknowledgments are added to the end of the preface without a separate heading. The word ACKNOWLEDGMENTS is placed 2 inches from the top of the page in all capital letters. Following a heading space, the acknowledgments begin. The text of the acknowledgments must be double spaced. In the acknowledgments, students may wish to recognize special assistance from committee members, friends, or family members who may have helped in the research, writing, or technical aspects of the thesis or dissertation. Research funding, grants, and/or permission to reprint copyrighted materials should be acknowledged. Individuals employed to prepare the manuscript are not acknowledged. 

The enumeration continues in sequence; no number appears on the first page. This is an optional entry. The word PREFACE is placed 2 inches from the top of the page in all capital letters. Following a heading space, the preface begins. The text of the preface must be double spaced. A preface includes the reasons for undertaking the study, the methods and design of the researcher, and acknowledgments. Background data and historical or other information essential to the reader’s understanding of the subject are placed in the text as an introduction, not in the preface. Theses and dissertations generally do not contain a foreword (i.e., a statement about the work by someone other than the author). 

This paper is in the following e-collection/theme issue:

Published on 15.5.2024 in Vol 26 (2024)

Rapport Building in Written Crisis Services: Qualitative Content Analysis

Authors of this article:

Original Paper

• Laura Schwab-Reese 1 , BSc, MA, PhD   ; 
• Caitlyn Short 1 , BSc, MPH   ; 
• Larel Jacobs 2 , MEd, MSc   ; 
• Michelle Fingerman 2 , MSc  

1 Department of Public Health, Purdue University, West Lafayette, IN, United States

2 Childhelp, Scottsdale, AZ, United States

Corresponding Author:

Laura Schwab-Reese, BSc, MA, PhD

Department of Public Health

Purdue University

West Lafayette, IN, 47907

United States

Phone: 1 765 496 6723

Email: [email protected]

Background: Building therapeutic relationships and social presence are challenging in digital services and maybe even more difficult in written services. Despite these difficulties, in-person care may not be feasible or accessible in all situations.

Objective: This study aims to categorize crisis counselors’ efforts to build rapport in written conversations by using deidentified conversation transcripts from the text and chat arms of the National Child Abuse Hotline. Using these categories, we identify the common characteristics of successful conversations. We defined success as conversations where help-seekers reported the hotline was a good way to seek help and that they were a lot more hopeful, a lot more informed, a lot more prepared to address the situation, and experiencing less stress, as reported by help-seekers.

Methods: The sample consisted of transcripts from 314 purposely selected conversations from of the 1153 text and chat conversations during July 2020. Hotline users answered a preconversation survey (ie, demographics) and a postconversation survey (ie, their perceptions of the conversation). We used qualitative content analysis to process the conversations.

Results: Active listening skills, including asking questions, paraphrasing, reflecting feelings, and interpreting situations, were commonly used by counselors. Validation, unconditional positive regard, and evaluation-based language, such as praise and apologies, were also often used. Compared with less successful conversations, successful conversations tended to include fewer statements that attend to the emotional dynamics. There were qualitative differences in how the counselors applied these approaches. Generally, crisis counselors in positive conversations tended to be more specific and tailor their comments to the situation.

Conclusions: Building therapeutic relationships and social presence are essential to digital interventions involving mental health professionals. Prior research demonstrates that they can be challenging to develop in written conversations. Our work demonstrates characteristics associated with successful conversations that could be adopted in other written help-seeking interventions.

Introduction

Since the 1990s, mental health providers have explored how to support clients via internet-based communication [ 1 ]. Prior work suggests that young people may be particularly interested in these approaches, as digital communication feels more private and emotionally safe [ 2 ]. However, internet-based communication, particularly written communication, may have significant barriers for providers and clients, including the inability to express emotion and challenges in communicating clearly [ 2 ]. Currently, there is limited evidence on how to overcome these communication issues in counseling settings [ 3 ]. Understanding how to do so may help telehealth providers build stronger therapeutic relationships, thus improving the help-seeking process. Further, this understanding may help agencies improve services and training for providers.

Technology-Based Mental Health Interventions

Technology-based (ie, telehealth) mental health services may not be as effective as in-person services. One recent meta-analysis suggests that videoconferencing-based therapeutic relationships may be inferior to those developed during in-person therapy [ 4 ]. However, there may be times when in-person care is not accessible or feasible. Nearly half of people in the United States live in a mental health shortage area, and there are areas with less than 2 psychiatrists per 100,000 residents [ 5 , 6 ]. As a result, increasing access to mental health care may depend on telehealth approaches. Within telehealth studies, interventions retaining elements of human contact are more effective than entirely computer-based interventions [ 7 , 8 ].

Two critical aspects of the helping relationship, therapeutic relationship and social presence, may be challenged when engaging digitally. A therapeutic relationship based on mutual trust, respect, empathy, and positive regard is essential in counseling [ 9 ]. Hundreds of studies have confirmed the importance of this collaborative relationship [ 10 ]. For most help-seekers, confidence in the provider, including perceptions of empathy and expertise, is key to developing a strong relationship [ 11 - 13 ].

Social presence [ 14 ], the sense of connecting and being with another, is another element that may be compromised during digital communication. Social presence may also be defined as the degree to which the other person feels “real” [ 15 ]. Although it is a natural element of face-to-face counseling, telehealth providers may have to be intentional in building a social presence. When conversing with unknown entities through written technology, it is common to question whether the other person is a human or a bot [ 16 ], in part because people are not reliably able to differentiate between the two [ 17 ]. Some prior work suggests that social presence is an important aspect of digital helping relationships because it assists in building therapeutic partnerships, professional bonds, and open communication [ 18 , 19 ].

Much of the literature on telehealth counseling focuses on verbal communication via videoconferencing or phone [ 20 ]. Few studies examine written mental health counseling services, and there is reason to believe that spoken and written communication are substantially different. In a recent review of the digital therapeutic relationship, Bantjes and Slabbert [ 20 ] suggest practical strategies for establishing rapport in digital spaces, such as maintaining eye contact, having high-speed internet to avoid lags, and attending to lighting and microphone placement. These strategies improve the audio and visual cues, which are not applicable to written communication.

Written Interventions

The literature on written counseling is limited [ 21 , 22 ]. In the 1990s, a small group of mental health providers offered therapy via email [ 23 ]. This early work identified several possible strengths and limitations. It was helpful for clients to write about their feelings, and the anonymity of email allowed them to share more openly. This asynchronous approach also increased many individuals’ sense of control, as they could choose when and where to engage with the therapist. Conversely, building a relationship and understanding nuances could be difficult without the usual social cues [ 23 ]. Two more recent literature reviews support many of the impressions formed by the early adopters, although most of the studies had very small sample sizes [ 22 , 24 ].

Written interventions may be challenging for the provider and patient, and both experience similar challenges. One randomized controlled trial of a chat-based cognitive behavioral therapy demonstrated reduced depression symptoms after 10 sessions [ 25 ]. In a parallel qualitative study, participants reported mixed perceptions of the experience [ 26 ]. Some reported feeling more able to share openly and process because of the anonymous platform. Others felt it was challenging to develop a relationship and express complex feelings and thoughts via writing [ 26 ]. Another study assessed differences between email-based cognitive behavioral therapy and unguided treatment. The email and unguided programs had better outcomes than the wait-list control group for some, but not all, outcomes [ 27 , 28 ]. Other studies, with and without in-person or telephone comparison groups, showed similarly mixed results [ 29 , 30 ]. In one unpublished dissertation, counselors who provided email services reported feeling substantial anxiety due to uncertainty, limited sensory information, and concerns about misunderstanding clients’ intentions [ 31 ]. The lack of visual, verbal, and social cues was particularly challenging [ 31 ]. They often focused more on the tasks and transactional aspects of helping to manage these uncertain dynamics [ 31 ]. Many also talked about needing much more time than usual to build the therapeutic relationship, although it did eventually happen for most [ 31 ].

Beyond mental health counseling, some recent work has examined written communication for brief counseling and advocacy [ 3 , 32 , 33 ]. Overall, privacy, autonomy, control, anonymity, and accessibility are seen as benefits of written services [ 34 - 36 ]. Building social presence and connection is an important aspect of the experience [ 34 ]. Often this professional connection builds over time, but because the help-seeker and crisis counselor or advocate do not have an ongoing relationship, it may be particularly difficult to communicate adequately and build a relationship [ 2 , 30 , 37 , 38 ]. Correctly understanding sarcasm, humor, and other nuanced language is particularly challenging in these brief interventions [ 3 , 39 ]. Like mental health counseling, the impact of written crisis and advocacy services is unclear in the current literature and may depend on geographical location, counselor training, and the help-seekers’ situations [ 33 , 40 - 46 ].

Study Purpose

Overall, establishing a human connection based on a strong therapeutic relationship and social presence will likely result in more effective, acceptable interventions. Providing crisis services is complex, and the confines of written communication create additional challenges. Rapport-building is particularly difficult, and mistakes may cause the help-seeker to feel worse [ 47 ]. However, there are not yet best practices for building rapport in these conversations, as existing approaches to rapport-building often depend on verbal and nonverbal cues [ 48 ]. As part of a larger study focused on building best practices for written hotlines, we worked with a child maltreatment-focused text or chat hotline. This analysis aims to categorize crisis counselors’ efforts to build rapport and convey active listening in written conversations. Using these categories, we identified characteristics associated with successful conversations, as reported by help-seekers. This work provides an important foundation for how to build therapeutic relationships in written mental health and hotline services.

Data Source

The data for this study are from the PACTECH (Prevent Abuse of Children Text and Chat Hotline), the text and chat arm of the Childhelp National Child Abuse Hotline [ 49 ]. Since 1982, Childhelp has offered 24/7 phone-based hotline services focused on support and resources related to child maltreatment. In 2018, the hotline expanded to include text and chat capabilities. Crisis counselors are employees rather than volunteers. Most are master-level professionals with specialized training in hotline services and child maltreatment. After conducting a quantitative pilot evaluation for 2 years, hotline leadership partnered with the lead author to use qualitative and mixed method approaches to identify best practices for services. As part of the data sharing agreement, the lead author and her research team received access to deidentified transcripts and metadata from conversations that were purposefully selected to represent a wide range of experiences and perceived outcomes.

Ethical Considerations

The Purdue University Institutional Review Board approved the research protocol (IRB-2020-965). The service terms and conditions disclosed that data may be shared with researchers. As a secondary data analysis of deidentified data, additional consent from participants was not required by the Institutional Review Board. The contract teams from Purdue University and Childhelp negotiated the terms of the data sharing agreement, including data security and access. As a result of the data sharing agreement, the data may not be released publicly.

The sample consists of 314 purposely selected conversations out of the 1153 text and chat conversations during July 2020. In addition to maintaining the written transcript of the conversation for 60 days, Childhelp collects preconversation and postconversation surveys from the help-seekers. The preconversation surveys focus on help-seeker characteristics (ie, age, gender, state of residence, and referral source), while the postconversation survey focuses on their perceptions of the conversation (eg, do they feel more hopeful, less stressed, and more prepared). We used maximum variation sampling to capture diverse help-seekers and outcomes, although not necessarily in the proportions present in the overall data [ 50 ]. This approach is particularly useful when looking for diverse perspectives, as was the case for our study. We sampled based on the preconversation and postconversation surveys. In our sample, 297 (94.6%) help-seekers answered at least 1 presurvey question, and 263 (83.8%) answered at least 1 postconversation survey question. First, we selected conversations where help-seekers reported that they were satisfied, unsatisfied, or mixed. We also included some conversations without surveys to reduce survey response bias. Then, we reviewed the demographic characteristics of the selected conversations to ensure help-seekers of different ages, races or ethnicities, and genders were included in the sample. For example, most help-seekers are girls, so there were relatively few conversations with boys in our initial sample. We added additional conversations with boys to ensure the results were not only relevant to girls.

We analyzed and reported the findings from all 314 conversations. When reporting quotes, however, we were particularly interested in the 45 conversations where help-seekers reported in the postconversation survey that the hotline was a good way to seek help and that they were a lot more hopeful, a lot more informed, a lot more prepared to address the situation, and experiencing less stress. Except when specifically referencing less successful conversations, all example quotes come from these conversations, as they represent those most successful from the help-seekers’ perspectives. All quotes are reported verbatim from the conversations, including any errors.

We used qualitative content analysis to process the conversations. We used both inductive and deductive processes to develop the codes. The first draft of the coding frame was based on our work with child maltreatment–related conversations within the Crisis Text Line [ 51 - 53 ]. Then, we revised the framework based on the content of the conversations.

Our development process followed the adaptation of grounded theory described by Schreier [ 54 ]. The lead author and her graduate research assistant reviewed all the conversations. During a second review of the conversations, we took notes on commonalities within the conversations, emphasizing material not captured in the first draft of the codebook. As we refined the codebook, all team members met weekly to discuss emerging materials and define and develop codes. After completing the framework and definitions, we coded 30 conversations and met to compare the code applications. We discussed differences in coding and refined the framework with the entire team. Then, we coded 30 additional conversations and assessed the coder agreement. After the second round of pilot coding, we reached 95% agreement on the codes and moved to code the full data set. In sum, we had 127 codes in the codebook, which were applied 22,326 times. After coding all the conversations, we reviewed the materials within each code. This process followed the segmentation process described by Schreier [ 54 ], where coded materials are decontextualized and reviewed to identify commonalities and themes. Through this process, we also assessed whether we met saturation, which occurs when all categories have been identified in the data set. Schrier’s [ 54 ] definition of qualitative content analysis saturation is different from other forms of qualitative methods. In other forms of qualitative analysis, saturation refers to the point at which reviewing additional material does not provide new information. We informally assessed this type of saturation by examining whether all codes were used if we considered only half of the sample. We found that all codes were used when we reviewed 2 different randomly selected split samples, which suggests that few new insights would be gained if we added additional conversations to our sample. After conducting these checks, we categorized the conversations by the outcomes and focused on similarities and differences across the groups.

For this analysis, we focused on the codes related to rapport building and active listening conversations. There were two main types of approaches used by crisis counselors: (1) counseling approaches and (2) evaluation-based language. Active listening skills, otherwise known as attending skills, are how counselors build connections with clients, express empathy, and convey that they are listening [ 48 ]. These skills may be defined slightly differently; asking questions, paraphrasing, reflecting feelings, and interpreting or summarizing the situation are generally recognized skills. We added validation [ 55 ] and unconditional positive regard [ 56 ], which are also commonly incorporated into helping relationships. Evaluation-based language, such as praise and apologies, is commonly used by adults when talking with children [ 57 ]. These statements differ from other approaches because the counselor’s evaluation of the situation is included.

We also examined how these approaches differed between the help-seekers most satisfied with the conversation (ie, answered all after-conversation survey questions as “Yes”) and those who were least satisfied with the conversation. We intended to define the least satisfied as those who answered all the after-conversation survey questions as “No.” However, only 4 people fit that criterion, so we included all help-seekers who answered most of the questions negatively.

Research Team

The research team included the lead author, a graduate research assistant, and 2 collaborators at Childhelp. The lead author is a family violence prevention researcher with a PhD in public health and an MA in counseling. She has experience conducting qualitative analyses of written hotline transcripts. The graduate research assistant was a master of public health student and had worked on the lead author’s research team for 3 years. She had experience with qualitative child maltreatment research. The Childhelp collaborators have substantial experience in hotline counseling and leadership. One has an MS in counseling psychology. The second has an MS in family and human development and an MEd in guidance counseling.

Help-Seeker Characteristics

Overall, our sample of help-seekers was generally similar to Childhelp’s overall text and chat users ( Table 1 ) [ 58 , 59 ]. Help-seekers tended to be female, young, and seeking help for themselves. Overall, they were generally at least a little more hopeful, informed, and prepared to deal with the situation after the conversation ( Table 2 ).

a Includes children who were distressed but did not necessarily describe events consistent with maltreatment.

a Do you feel more positive or hopeful after this chat/text session?

b Did you get the information you needed from this chat or text session?

c Do you feel better prepared to deal with the situation after this chat or text session?

d Do you feel less stress after the chat or text session?

e Was using chat or text a good way for you to get help?

Active Listening Skills

Paraphrasing information and feelings.

When paraphrasing (387 times across 170 conversations), the crisis counselor repeated what was said by the help-seeker in a way that honed the focus of the conversation. Often, it included the most important words shared by the help-seeker, along with a shortened, clarified version of the essential information or feelings. For example, when seeking to understand the situation, a crisis counselor said, “It does not sound like she is able to listen to your needs and wants at this time.” At other times, the crisis counselor wanted to convey that they have been listening. Saying, “...you mentioned that they are screaming at him and from what you have said it sounds like they might be being really aggressive with him” demonstrated that they have been paying attention to the information shared.

Sometimes, the crisis counselors reflected the feelings shared by the help-seeker, saying things like, “That sounds like it can be frustrating from what you shared,” “it sounds very overwhelming and scary,” or “I can see how stressful this is.” In these situations, the crisis counselor was often distilling the feelings to support the help-seeker in identifying what is most bothering them about the situation or what feeling is driving their response to the situation. Once the help-seeker recognized the most troubling aspect of the situation, they were often more able to brainstorm ways to address it with the crisis counselor.

Interpretation

Interpreting the situation was also common (236 times across 125 conversations). Often, help-seekers were confused or had ambivalent thoughts about the situation. In these cases, they usually struggled to identify the next steps or reduce their emotional activation. By interpreting the situation, the crisis counselors offered a coherent overview of the situation and a different perspective. In most active listening skills, crisis counselors stayed quite close to the information provided by the help-seeker (eg, paraphrasing or reflecting what was said). When interpreting the situation, crisis counselors often included their perspectives on the situation with the intent of supporting the help-seeker to see themes or new ideas. For example, one help-seeker shared that their caregivers regularly say hurtful things about their gender identity and sexual orientation, scream and yell, and tell the help-seeker that they are a disappointment. In response, the crisis counselor said, “Sounds like it would be very hard to be happy living with people who treat you like that.” Although the help-seeker had not overtly shared about their unhappiness, this interpretation led to the help-seeker sharing about active suicidal ideation.

Open Questions

Open questions (208 across 124 conversations) served multiple purposes. At the beginning of the conversations, they invited the help-seeker to share about the experience. For example, “Could you tell me what’s going on?” or “What’s making you feel unsafe?” was used to begin the conversation in a nonthreatening way. As the conversation moved to explore the issues, open questions could elicit specific details (eg, “What’s happened since then?” and “What does that mean?”) or focus attention on feelings (eg, “How does it make you feel when your mom lashes out?” and “How are you feeling about all this happening?”).

Other Common Counseling Approaches

Validation was the most used approach to active listening (647 times across 226 conversations), and it took many forms depending on the situation. Throughout the conversations, it was used to affirm the help-seeker, their feelings, and their thoughts. For example, one counselor said, “It can be hard living in a house where you don’t feel supported and respected.” In this situation, the help-seeker had a difficult relationship with a father, who regularly called the help-seeker “overdramatic or a crybaby.” By validating the difficulty of feeling unsupported, the crisis counselor communicated that the help-seeker and their feelings were important.

In other instances, the crisis counselor validated the help-seeker’s perspectives about what was or was not appropriate behavior within families. In one instance, a help-seeker shared concerns about an older sibling’s treatment of an infant. The brother was rough with the infant and burned the infant with hot milk. In response, the crisis counselor said, “I can see why you would be concerned for the baby’s safety.” In doing so, the crisis counselor communicated that the help-seeker’s feelings were valid but without confirming that the infant was being maltreated. The crisis counselor had not seen evidence of the situation, so they could not accurately validate whether the infant was being maltreated. Simple phrases, such as “I hear you. This is difficult,” “That must be really hard for you,” and “It’s okay to feel stressed that is normal,” also validated the help-seeker and their perspectives.

Unconditional Positive Regard

Unconditional positive regard (102 times across 66 conversations) occurred when crisis counselors provided basic acceptance and support of the help-seeker, regardless of their behavior or things that have been done to them. Unconditional positive regard primarily focused on the abuse experience. It was common for counselors to say things like, “No one deserves to be abused” or “No one deserves to be treated like that.” These statements were often particularly well received by help-seekers, like this example:

You don’t deserve to be emotionally abused. It’s not o.k. [Counselor]

Thank you for saying that. You are the first person ive ever talked about this personally with. [Help-seeker]

Evaluation-Based Language

Evaluation-based language involved a judgment by the crisis counselor about whether an aspect of the help-seekers’ experiences was good (eg, behavior worthy of praise) or bad (eg, an apology for something that happened to the help-seeker). Evaluation and judgment are generally not a part of helping relationships [ 48 , 60 , 61 ] but are quite common when adults speak with children [ 57 , 62 ]. Although these approaches are not generally part of counseling relationships, there is nothing inherently wrong with using them intentionally.

Praise (268 times across 145 conversations) occurred when the crisis counselor conveyed that they approved of the help-seekers or their behavior. Sometimes, praise focused on the behaviors occurring during the conversations, like “Thank you for sharing with me” and “I’m glad you reached out today.” At other times, the praise centered on behaviors that they would do in the future, such as “Yes, I believe you’re doing the right thing by calling)” and “I think that will be a good move for you.”

Apologies (372 times across 213 conversations) tended to focus on the help-seeker’s situation or issues with the hotline. Apologies for the hotline were usually about a technical difficulty (eg, “sorry, our system is not working well”). Apologies about the help-seeker’s situation could be very broad, such as “I’m so sorry to hear about all of this” and “I’m so sorry that you’re having to go through this.” Apologies could also be specific to the situation, like “I am sorry to hear Mom yelled at you yesterday too.”

Differences Between Successful and Less Successful Conversations

There were some differences in active listening skills, other counseling skills, and evaluation-based language between successful and less successful conversations. Although the sample of successful and less successful conversations was too small for formal statistical analysis, some commonalities emerged. First, although conversations were approximately the same length, less successful conversations tended to have more statements that attended to rapport building. Second, there were also differences in how the counselors applied these approaches. Unlike the preceding sections, this section includes quotes from both successful and less successful conversations.

Overall, counselors in less successful conversations tended to be vague or to directly repeat what was said by the help-seeker. These differences were particularly apparent when counselors were paraphrasing, asking open questions, or apologizing. For example, paraphrasing in less successful conversations tended to be either very vague (eg, “It sounds like you are being hurt already”) or very specific (eg, “I am hearing you have some future plans to get a job and earn your own money...”). In the last example, the help-seeker used the same phrasing in their previous statement. Conversely, successful conversations tended to be specific without direct repetition (eg, “Sounds like they are something to help you cope”). Similarly, less successful conversations tended to include open questions that were either broad (eg, “What’s happening?”) or focused on clarifying how the crisis counselor could help (eg, “How are you hoping that I can help?”). Some successful conversations also included questions clarifying how the crisis counselor could help, but it was more common to ask more specific questions, like “What is it that you would like to vent about?” and “What are their thoughts on CPS involvement?” Finally, crisis counselors used generally vague apologies about the situation in less successful conversations. Saying things like “I am so sorry this happened to you” or “I’m sorry to hear that” was common. Although some successful conversations also included these types of apologies, it was more common to pair the apology with a specific reason, such as “I’m so sorry that you have been experiencing this for so long” or “I am sorry to hear Mama is sick.”

Principal Results

Overall, our study suggests that it is possible to build therapeutic relationships via a text and chat hotline with individuals seeking child maltreatment–related information and support. Approximately 15% (n=45) of our sample reported that the hotline was a good way to seek help and that they were a lot more hopeful, a lot more informed, a lot more prepared to address the situation, and experiencing less stress. However, our sample was intentionally selected to represent a wide range of help-seeker perceptions, so this does not indicate that 15% of the hotline’s help-seekers felt this way. Based on the 2022 Childhelp data report, about 85% of help-seekers reported getting the information they needed, 80% of help-seekers reported feeling more hopeful after the conversation, and 75% reported feeling better prepared to deal with the situation [ 59 ]. These percentages suggest that the hotline provides a well-received service.

Generally, counselors built rapport through active listening skills, other counseling techniques, and evaluation-based language (ie, apologies, praise). Through active listening skills and other counseling techniques, counselors often expressed that they were listening, wanted to understand the help-seekers, and cared for them. They expressed their approval or disapproval of the help-seekers and aspects of their experiences through evaluation-based language. Although there is nothing inherently wrong with using apologies and praise, they tend to be avoided in many therapeutic approaches. Praise may undermine intrinsic motivation (ie, internal drive) and reduce engagement in the process [ 63 - 65 ]. Further, these types of evaluation-based language are rooted in control, as they are given based on something that another individual (ie, the crisis counselor) deems desirable [ 63 ]. As a result, the help-seeker might seek praise by giving answers that they believe the crisis counselor wants to receive instead of accurate answers, which may reduce the benefit of the conversation. However, praise and compliments may be a quick way to build encouraging feelings [ 66 ]. As it is challenging to build relationships via writing, praise may be one way to build a relationship quickly. Additional research into the impact of evaluation-based language is necessary to understand its role in written crisis counseling.

There were some differences between successful and less successful conversations. Surprisingly, less successful conversations tended to include more attending language than successful conversations. However, there were differences in the ways that crisis counselors apply these techniques. Overall, the crisis counselors in successful conversations tended to be more specific and tailor their responses to the help-seekers. Possibly, counselors who gave tailored responses built rapport more quickly; thus, fewer attending statements were required. If this is the case, they could move to problem-solving more quickly, which may also contribute to help-seekers’ perceptions that they were more prepared to address the situation and were more informed. These tailored responses may increase help-seekers’ perceptions that the crisis counselor is invested in the conversation. Several help-seekers explicitly asked if they were speaking with a bot in this sample. Having tailored responses may increase crisis counselors’ social presence and reduce help-seekers’ concerns about whether they are “real.” As organizations consider using large language models and chatbots in these types of services, careful attention should be given to help-seekers’ perceptions about the service and its appropriateness for the audience. As the National Eating Disorders Association learned when its wellness chatbot began providing diet information, large language models trained on outside data may not be a good fit for conversations with help-seekers [ 67 ].

Limitations

Our work has several limitations, including some inherent to secondary data analysis. First, we could not speak with the help-seekers or the counselors about the conversations. Although we were able to identify similarities across well-received conversations, it is possible that other aspects of the conversations contributed to help-seekers’ perceptions. Second, we do not know how these conversations shaped long-term outcomes. Moreover, it is difficult to follow up with help-seekers, as evidenced by the 6% response rate to a 2-week follow-up survey conducted by the National Domestic Violence Hotline [ 68 ]. Further, many of the help-seekers in this sample indicated that it is unsafe to speak aloud about their experiences, so qualitative data collection with this sample would likely have an even lower response rate. It would be more feasible to speak with counselors about their experiences, but their perspectives may be disconnected from those of the help-seekers. Despite this limitation, we incorporated the help-seekers’ perspectives through the postconversation survey, which is more than is usually possible in secondary data analysis.

Our work may not generalize to conversations unrelated to child maltreatment. As a child maltreatment–specific hotline, all conversations included elements of child maltreatment. Conversations about other topics may require other approaches. However, our results are consistent with prior work on building rapport in other forms of counseling [ 48 , 55 , 56 ], so it is reasonable to expect these findings would translate to written conversations about other topics.

Comparison With Prior Work

To the best of our knowledge, there is no other work examining specific ways to build a therapeutic relationship in written mental health counseling or crisis counseling. However, the ways that crisis counselors attended to the dynamics of the conversations were generally like those found in in-person counseling [ 48 , 55 , 56 ].

Telehealth approaches to counseling may be particularly important for young people experiencing maltreatment. Other formal resources, such as law enforcement, schools, and child protection systems, often fail to respond adequately [ 53 , 69 , 70 ]. Further, internet-based approaches, particularly written approaches, are highly acceptable to young people experiencing maltreatment [ 69 ]. In our sample and past research, children shared that they could not call resources because an audible conversation would cause parents to know they were seeking help. In work conducted with Crisis Text Line, it was common for young people sharing child maltreatment to report that the abuse escalated when parents discovered their attempts to seek help. Written, anonymous communication that is available 24/7 may be a safer way for these young people to seek help. Thus, written communication may be particularly important for children in unsafe homes.

There is also limited evidence on how to respond when young people share maltreatment experiences. Regardless of the ability to impact or end the maltreatment, individuals who receive a child maltreatment disclosure need to receive an appropriate, supportive response [ 71 - 74 ]. Supportive responses encourage the young person experiencing maltreatment to reframe their experience, which substantially reduces the likelihood of poor outcomes otherwise associated with maltreatment [ 75 ]. Conversely, unsupportive experiences often have long-lasting consequences [ 74 , 76 ]. Receiving a hurtful or unsupportive response increases the likelihood that the young person will experience more significant physical and mental health issues [ 74 , 76 , 77 ]. Unfortunately, many young people receive unsupportive responses to their disclosures [ 53 , 70 ]. Often, they report that others, particularly adults, do not believe them and are unwilling to help [ 70 , 78 ]. These experiences reduce their willingness to seek help or share their experiences in the future [ 70 ]. Our work suggests that responding to these disclosures adequately in written conversations is possible.

Our work also contributes to a small body of literature on using text and chat hotlines to provide services to people experiencing violence more generally. Michigan State University added chat services to its existing sexual assault support and advocacy hotline. Their evaluation was consistent with many of the benefits and limitations of other forms of written counseling, including challenges with nuance, misunderstanding written language, and communicating empathy [ 3 ]. However, the format also gave help-seekers a greater sense of control [ 3 ]. Another study focused on agencies providing digital violence-related support and advocacy services [ 32 ]. This work also emphasized the importance of clear communication and building rapport, although help-seeker perceptions of these factors were not assessed [ 32 ].

Conclusions

Building therapeutic relationships and social presence are important components of digital interventions involving mental health professionals. Prior research suggests that they can be challenging to develop in written conversations. Our work demonstrates characteristics of conversations associated with greater satisfaction among help-seekers. These findings may be adopted by other organizations building mental health or support interventions that include written communication. However, additional research is needed to identify how to train providers to adopt these strategies while also tailoring their approach to the help-seeker. Further, our findings may inform future work with large language models, including how large language models could contribute to these interventions. However, future research is needed to understand how help-seekers would interface with these methods and to ensure that the models consistently convey appropriate, supportive information.

Acknowledgments

This project was supported by the Children’s Bureau (CB) and Administration for Children and Families (ACF) of the US Department of Health and Human Services (HHS) as part of a financial assistance award in the amount of US $6,000,000 that was 100% funded by the CB and ACF of the HHS. The contents are those of the authors and do not necessarily represent the official views of, nor an endorsement by, the CB and ACF of the HHS or the US government. For more information, please visit administrative and national policy requirements.

Conflicts of Interest

None declared.

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Edited by T de Azevedo Cardoso; submitted 19.08.22; peer-reviewed by K Zhang, V Franzoni, B Li, Z Aghaei; comments to author 28.03.23; revised version received 21.08.23; accepted 26.03.24; published 15.05.24.

©Laura Schwab-Reese, Caitlyn Short, Larel Jacobs, Michelle Fingerman. Originally published in the Journal of Medical Internet Research (https://www.jmir.org), 15.05.2024.

This is an open-access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work, first published in the Journal of Medical Internet Research, is properly cited. The complete bibliographic information, a link to the original publication on https://www.jmir.org/, as well as this copyright and license information must be included.

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Original research article, microwave biosensor for the detection of growth inhibition of human liver cancer cells at different concentrations of chemotherapeutic drug.

• 1 School of Internet of Things Engineering, Institute of Advanced Technology, Jiangnan University, Wuxi, China
• 2 State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China
• 3 Key Laboratory of Biopharmaceutical Preparation and Delivery, Chinese Academy of Sciences, Beijing, China
• 4 School of Biotechnology, the Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi, China

Cytotoxicity assays are crucial for assessing the efficacy of drugs in killing cancer cells and determining their potential therapeutic value. Measurement of the effect of drug concentration, which is an influence factor on cytotoxicity, is of great importance. This paper proposes a cytotoxicity assay using microwave sensors in an end-point approach based on the detection of the number of live cells for the first time. In contrast to optical methods like fluorescent labeling, this research uses a resonator-type microwave biosensor to evaluate the effects of drug concentrations on cytotoxicity by monitoring electrical parameter changes due to varying cell densities. Initially, the feasibility of treating cells with ultrapure water for cell counting by a microwave biosensor is confirmed. Subsequently, inhibition curves generated by both the CCK-8 method and the new microwave biosensor for various drug concentrations were compared and found to be congruent. This agreement supports the potential of microwave-based methods to quantify cell growth inhibition by drug concentrations.

1 Introduction

Cytotoxicity assays are pivotal in evaluating cellular damage induced by drugs, playing a critical role in the drug development process and safety evaluation ( Parboosing et al., 2017 ; Zhang and Wan, 2022 ). These assays facilitate the determination of a drug’s safety profile, therapeutic window, and potential side effects, thus informing drug design, judicious usage, and toxicity risk assessment. They are instrumental in detecting adverse effects and providing essential data for the secure administration of drugs ( Niles et al., 2008 ; Vaucher et al., 2010 ).

The relationship between drug concentration, an independent factor influencing cytotoxicity ( Chan et al., 2002 ; Radko et al., 2013 ), and cytotoxicity is essential to optimize therapeutic efficacy and minimize adverse effects. Understanding the dose-response relationship is pivotal for researchers to strike a delicate balance between drug efficacy and safety, thereby ensuring judicious drug utilization that curtails potential risks. Cancer cells differ from normal cells in many ways, one of which is that they grow and divide very rapidly. In response to this characteristic, a number of cytotoxic drugs have been developed that target rapidly proliferating cancer cells and inhibit their growth and proliferation by interfering with their DNA synthesis or cell division processes ( McQuade et al., 2017 ; Dongsar et al., 2023 ). However, cytotoxic drugs do not completely discriminate between cancer cells and normal cells ( Tofzikovskaya et al., 2015 ). Mitomycin-C is an example of a cell cycle-specific chemotherapeutic agent widely used in oncology and cytotoxicity research ( Tomasz, 1995 ; Zhang et al., 2019 ; Park et al., 2021 ), predominantly acting on the G2 and M phases to impede DNA synthesis and cell division, thereby arresting cancer cell proliferation. Despite its efficacy against various cancer cell types, mitomycin-c’s potential toxicity to normal cells necessitates rigorous dose regulation and vigilant monitoring for adverse effects. Consequently, assessing the drug concentration-inhibition relationship is an indispensable component of cytotoxicity studies.

To accurately evaluate drug impacts on cell viability, two common techniques are employed: real-time cellular analysis (RTCA) and CCK-8 assays ( Cai et al., 2019 ). RTCA offers real-time, non-invasive monitoring of cellular dynamics, but with limited application scope and higher equipment costs ( Yan et al., 2018 ). Conversely, the CCK-8 assay, a standard in cytotoxicity tests, facilitates straightforward colorimetric measurements and is versatile across various cell lines ( Wang et al., 2015 ; Liu et al., 2018 ; Wang et al., 2018 ). However, to ensure a sufficient reaction, the CCK-8 method requires a certain incubation time for the reaction, typically 1∼4 h.

While established cytotoxicity assays like CCK-8 and real-time cellular assays are well-developed, ongoing research is delving into novel assays tailored for diverse cellular contexts and specific experimental requirements. The investigation of cytotoxic mechanisms warrants detailed analysis in certain studies, whereas others prioritize the rapidity and precision of the assay’s readouts. Moreover, optical and electrical measurements can often complement each other’s results in the field of biosensing ( He et al., 2023 ). Microwave biosensors, as a new type of biosensor, are highly sensitive and correspondingly fast (their response time is usually only a few seconds to a few mins), allowing real-time results to be obtained in a short period of time ( Narang et al., 2018 ; Gao et al., 2021 ). Microwave biosensors’ compactness and lightweight design indeed make them ideal for portable device production. Their seamless integration with electronic circuits, coupled with appropriate algorithms, can lead to intelligent data processing products. To date, no attempt has been made to detect drug cytotoxicity using microwave resonance sensors. If the microwave biosensor can be used for cytotoxicity detection, it can complement the original method in terms of advantages and disadvantages. This wound also further broaden the application areas of microwave detection. Microwave biosensors for measuring cytotoxicity have the advantages of eliminating the need for cell staining, rapid detection, low cost, easy integration with matching circuits, and small sample size. Microwave sensors based on resonant elements are very sensitive to the dielectric constant and loss angle tangent of the surrounding medium ( Muñoz-Enano et al., 2020 ), and have been widely used in the fields of biosensing. Researchers have demonstrated that it has promising applications in bacteria detection ( Narang et al., 2018 ; Jain et al., 2020 ; Jain et al., 2021 ), blood glucose detection ( Yilmaz et al., 2019 ; Kandwal et al., 2020 ; Nazli Kazemi anLight, 2023 ), and many other areas. Since the key to the endpoint method of evaluating drug cytotoxicity is to determine the number of surviving cells at the end of the experiment ( Adan et al., 2016 ), and there have been studies on the differences in dielectric properties of cell solutions at different concentrations ( Chen et al., 2014 ), it has a certain degree of feasibility to do cytotoxicity testing with microwave sensors.

In this paper, we have designed and fabricated a microwave biosensor based on the integrated passive device (IPD) fabrication technology. IPD integrates different passive components (inductors, capacitors, resistors) in a single subcomponent, which is characterized by a small linewidth, precise substrate control, a high degree of integration and fewer parasitic effects ( Yu et al., 2019 ; Chu et al., 2020 ). Moreover, IPDs demonstrate enhanced stability compared to capacitive or resistive sensors ( Yu et al., 2021 ). The consolidation of multiple passive components onto a single chip allows IPDs to conserve space, diminish energy consumption, bolster system reliability and accuracy of measurements, and ease the transition to productization. Employing this biosensor, we assessed the impact of concentration on cytotoxicity using HepG2 cells as the model and Mitomycin-c as the chemotherapeutic agent. We determined OD450 values via the CCK-8 assay, which is the biological gold standard ( Zhou et al., 2018 ), as a control group for parallel experiments and verified the feasibility of cytotoxicity experiments using microwave sensors by mapping and comparing the curves of the two groups. In addition, we treated the cells with ultrapure water instead of phosphate buffered saline (PBS) in this experiment to verify the feasibility of this treatment in the microwave biosensor cell number measurement experiments.

2 Materials and methods

2.1 sensor design and analysis.

The proposed biosensor is a microwave IPD resonator, consisting of a spiral inductor and an interdigital capacitor, where changes in the electrical parameters of the surrounding medium, mainly the dielectric constant and the loss angle tangent can cause changes in the resonant frequency or the amplitude of the resonance peak. When designing microwave resonators, the relevant parameters and performance are usually adjusted by the capacitance section ( Zhu and Abbosh, 2016 ; Xu and Zhu, 2017 ). The spiral inductor of the proposed microwave sensor is pre-designed by our group ( Wang et al., 2023 ) and this work focuses on the design, optimization and simulation of the interdigital capacitor. By adjusting the corresponding capacitance structure, we can adjust the frequency sensitivity and amplitude sensitivity of the resonator. In the design of the interdigital capacitive structure, three schemes are considered, respectively, in a cross-shaped central periphery equally spaced increase of 1-turn, 2-turn and 3-turn copper strip lines as shown in Figures 1A–I, B-I, and C-I . The reflection coefficient (S 11 ) of the three resonators and the variation of the resonance peak amplitude in different loss angle tangent environments are simulated in the Advanced Design System 2020 (ADS). The Eq. (1) shows that the permittivity of a sample can be obtained by adding the real and imaginary permittivity:

Figure 1 . Simulation results of the sensor. (A) Interdigital capacitor with 1-turn, (A–I) structure, (A-II) S 11 , (A-III) resonance peak amplitude in different loss angle tangent. (B) Interdigital capacitor with 2-turns, (B–I) structure, (B-II) S 11 , (B-III) resonance peak amplitude in different loss angle tangent. (C) Interdigital capacitor with 3-turns, (C–I) structure, (C-II) S 11 , (C-III) resonance peak amplitude in different loss angle tangent.

The loss angle tangent is calculated from Eq. 2 :

Samples with varying cell concentrations can be characterized by using different values of the loss angle tangent. A change in the loss angle tangent indicates a change in the complex dielectric constant, which in turn affects the S 11 of the microwave resonator. It can be seen from Figures 1A–II , B-II, and C-II that as the number of turns increases, the resonant frequency decreases, the bandwidth decreases and the Q value decreases. High Q represents high energy storage capacity and frequency selectivity. In terms of sensitivity to the loss angle tangent, the structure of 2-turn shows the best performance as illustrated in Figures 1A–III , B-III, and C-III. Since the resonance amplitude is usually the preferred metric for this type of detection relative to the resonance frequency ( Jain et al., 2021 ), and combined with factors such as the size of the detection area, interdigital capacitor with 2-turns was finally selected as the biosensor.

Figure 2A delineates the capacitive section’s architecture and precise dimensions. Encircling the device, a spiral inductor integrated with air-bridge structures is observed, while at its nucleus lies an interdigital capacitor, composed of strip wires coiled around a cruciform framework. The strip lines boast a uniform size and interspace of 20 μm. Figure 2B shows the longitudinal layer structure of the sensor, from top to bottom, with a 4.5/0.5 µm Cu/Au top layer, a 1.8 μm copper interconnect layer containing air bridge structure which were introduced in the spiral inductor to increase the mutual inductance and decrease the signal transmission loss in the inductor, a 4.5/0.5 µm Cu/Au bottom layer, a 0.2 μm thick nitride dielectric layer with relative dielectric constant of 7.5 and a loss angle tangent of 0.0036, a 200 μm thick GaAs substrate layer with relative dielectric constant of 12.85 and a loss angle tangent of 0.0028. For the fabrication of our proposed biosensor, seed metal (Ti/Au) is sputtered with the thicknesses of 20/80 nm as for strengthened metallic adhesion. In the electroplating process, gold and copper are tightly bonded through the plating process and have excellent corrosion resistance and do not easily diffuse into the solution, thus they do not interfere with the cytotoxicity analysis of cells. The electric field condition of this resonator is simulated in High Frequency Structure Simulator 19.1(HFSS), and its horizontal E-field strength is shown in Figure 2C , where the E-field strength reaches 10 6  V/m in its core sensitive region. The highest electric field strengths reported so far in the paper are around 10 5  V/m ( Zarifi et al., 2017 ; Kumar et al., 2020 ). The device’s notably higher electric field strengths suggest enhanced penetration and sensitivity. Considering the actual measured solution droplet size, the longitudinal field strength distribution is also simulated, and the results are shown in Figure 2D , illustrating that the sensitive region can still achieve an electric field strength of 10 5  V/m at a height of 50 μm. High electric field strength in the horizontal and vertical directions reveals the good penetration capability of the device. Consequently, this allows for the use of larger droplet volumes when applying sample droplets, effectively minimizing random sampling errors. Figure 2E shows the equivalent circuit diagram of the device. The capacitance of the oxide layer between the base and the metal can be denoted as C ox , the resistance between the substrate and the ground can be denoted as R sub , the capacitance can be denoted as C sub , the parasitic resistance of the inductor can be denoted as R L , the parasitic conductance of the capacitance can be denoted as G . Through the equivalent circuit transformation, the whole device can be regarded as an LC resonator. The complex dielectric constant properties of the cell solution can be modeled using the Debye equation. The relationship between the measured microwave parameters of the cell solution and the complex dielectric constant can be expressed by Eq. (3) as ( Withayachumnankul et al., 2013 )

where △ ε ′ = ε s ′ − ε r ′ , △ ε ″ = ε s ″ − ε r ″ , △ f 0 = f s − f r and △ S 11 = S 11 s − S 11 r are the differences between the sample (with subscript s ) and the reference (with subscript r ) values, m 11 , m 12 , m 21 , m 22 is the parameters to be determined. In this experiment, a change in cell concentration would cause a change in the loss angle tangent, thus causing a change in △ S 11 .

Figure 2 . Device structure analysis and electric field simulation. (A) Overall device structure and dimensions of interdigital capacitance. (B) The hierarchical structure of the device. (C) Surface electric field distribution of devices. (D) Vertical electric field distribution. (E) Equivalent circuit diagram.

2.2 Preparation of biological sample

HepG2 cell line is used as the experimental cells which were purchased from the cell bank of the Chinese Academy of Science (Shanghai, China). It is a human hepatocellular carcinoma cell line commonly used in the study of molecular mechanisms, drug screening and treatment of liver cancer ( Elkady et al., 2022 ). The entire experimental procedure is illustrated in Figure 3 . After completing the cell resuscitation, we first performed a pre-experiment using the fabricated microwave biosensor for cell number measurement. We inoculated cells into rows A, B, D, and E of a 96-well plate with a concentration gradient of 100 cells per well to 200,000 cells per well in two-fold increments, and added.

Figure 3 . Cell culture and handling, addition of drugs and pre-preparation for measurements.

Dulbecco’s modified eagle medium (DMEM) to make them adherent to the bottom by incubating them for 24 h in a CO 2 incubator at 37 °C. After removing them from the incubator, we pipetted the DMEM from the A and B rows and washed them with PBS. After that, in row A, trypsin treatment was used to dissociate the cells from the bottom, and then 100 μL of PBS was injected into each well; in row B, the same trypsin treatment was used, and then 100 μL of ultrapure water was injected into each well. Rows D and E are used as backup groups. The PBS, trypsin solution and DMEM used in the experiments were purchased from Sangon Biotech (Shanghai, China). The cell culture incubator was purchased from Thermofishe (United States). Normally, in cell number experiments, cells are treated in PBS.In this study, ultrapure water was utilized to treat Group B based on several key considerations. In order to maintain an isotonic state with the cytosol, the ionic concentration of PBS buffer and cytosol is similar. This would result in the cells and the PBS potentially exhibiting similar electrical parameter characteristics, which will lead to a narrowing of the differences in electrical parameters caused by the concentration of the cells. Conversely, the contrast in ionic concentration between ultrapure water and the cell solution is likely to amplify the solution’s electrical parameter changes due to cellular quantity. On the other hand, cell water uptake and cell fluid exudation can result in a more uniform ionic distribution of the solution, thus mitigating random errors linked to small sample sizes. After completing the pre-experimental validation, we seeded 50,000 cells per well on a new 96-well plate, inoculated on row C, D and E as three parallel groups, and after 24 h of CO 2 thermostatic incubation for cell adhesion, drug administration commenced. In this experiment, we used mitomycin-c as an inhibitor of cell growth. Mitomycin-c was selected as the cell growth inhibitor for this experiment. It was initially dissolved in dimethyl sulfoxide before being prepared into a stock solution at various concentrations. This stock solution was then serially diluted with DMEM to create a two-fold concentration gradient ranging from 1.7 μmol/L to 40 μmol/L. Subsequently, 200 μL of DMEM containing varying concentrations of mitomycin-c was added to each well of the 96-well plate and incubated at 37°C in a CO 2 incubator for 48 h. Repeat the above steps and prepare the same 3 rows of cells on a new 96-well plate, with one set for OD450 optical measurements and the other set for microwave measurements. For microwave measurement groups, remove the DMEM with a pipette, wash it with PBS, inject 100 μL of ultrapure water into each well. After a period of resting, pipette 1.5 μL of solution and drop it on the sensor for detection. Since the proposed microwave biosensor performs cytotoxicity detection mainly by detecting the concentration of ions contained in the cells, it is unable to distinguish between live and dead cells. Therefore, it is important to ensure that dead cells are cleaned as completely as possible before measurement. Additionally, the ions in the drug can also affect the measurements, so it is important to ensure that the drug is completely purified. The mitomycin-c and dimethyl sulfoxide used were purchased from MedChemExpress (Shanghai, China).

2.3 Experimental environment

The experimental apparatus was positioned on an anti-static mat and comprised a Vector Network Analyzer (VNA, Ceyear, 3656B), the IPD device, coaxial cables, samples, and a pipette, as depicted in Figure 4A . At the heart of the IPD device lies the microwave resonator, detailed microstructurally in Figure 4C . The resonator’s two ports are connected by bonding wire to the corresponding input and output matching wires on the printed circuit board. Figure 4B schematically illustrates the assembled sensor. Its bottom is an aluminum block with screw holes for fixing holes, and the chip is first fixed on top of the aluminum block by screws, and then connected to the coaxial cable of the VNA through the Small A Type connector fixed on both sides. This meticulous assembly ensures the chip remains horizontally stable, mitigating positional errors. The coaxial cable itself is taped to the table to reduce measurement disruptions from any movement. During the measurement, 1.5 μL of solution was added to the middle sensing area with a pipette. To ensure uniform distribution and mitigate the risk of sample settling, each sample drawn from a 96-well plate via pipette is agitated by employing a larger pipette tip. In subsequent sample drops, it was found that when the droplet volume was equal to 2 μL or larger, the droplets were easy to be dispersed irregularly on the surface of the device leading to measurement failure due to destruction of the surface tension of the droplets. After each measurement, the liquid was sucked up with absorbent paper and was cleaned several times with ultrapure water to return the S 11 to the initial values to ensure that the next experiment was not affected. Since temperature and humidity affect the performance of semiconductor devices, we control and measure the temperature and humidity values, the measurements were carried out at an ambient temperature of 20°C∼21 °C and a humidity of 47 %RH∼48 %RH.

Figure 4 . Measuring platforms and fabricated sensor. (A) The measurement environment. (B) Device structure and assembly schematic. (C) Microscope image of the proposed sensor.

3 Results and discussion

3.1 pre-experimental results of cell number measurements.

Figure 5 shows the overall results of the cell number measurement experiment. In the cell number measurement pre-experiment, pictures of cells with concentration gradients from 6.4×10 4 /mL to 2×10 6 /mL were taken under the microscope as shown in Figure 5A∼F , which showed healthy growth and a clear concentration gradient. The cells with a concentration gradient from 1×10 4 /mL to 3.2×10 4 /mL did not show a marked difference due to the limited cell numbers, similar to 6.4×10 4 /mL. Figure 5G illustrates the cellular morphology in PBS, where a transition from wall-adherent irregular shapes to more defined round or ovoid forms is observed, predominantly existing as either single entities or aggregated clusters. Under this circumstance, a dynamic equilibrium of ion and water molecule exchange is established between the intracellular and extracellular environments, resulting in comparable ion concentrations. Figure 5H shows the status of the cells after 5 mins of exposure to ultrapure water. Due to the lower osmotic pressure of pure water compared to the cells, water enters the cells, causing them to swell or even dissolve. Cells lose their original morphological characteristics in pure water and become flattened, deformed or ruptured. This can lead to spillage of cell contents dispersed in ultrapure water. The measurements of the S 11 near the resonance peak of ten quantities of cells after treatment with ultrapure water are shown in Figure 5I . The peak value of the S 11 decreases with the increase of cell concentration. These measurements were plotted as points in Origin. It can be found that when the number of cells is too low (lower than 6.4 × 10 4 /mL), the measurements of microwave amplitude are similar, showing a deviation from the other groups and are similar to the measurements of ultrapure water. This may be due to inadequate cytosol exchange with external components when cell numbers are low, and the aspirated 1.5 μL solution may not contain cell membrane components. After selecting the mean of multiple measurements, we performed a linear fit to the mean data on the last six data as shown in Figure 5J . The error bars are based on the mean value, and the relationship between the amplitude of the resonance peak and the concentration of the cells can be characterized by y = 2.58549 × 10 −7 x-25.70623. R 2 is 0.99874, showing a good linear relationship. The corresponding detection and quantification limits (LOD&LOQ) of the proposed devices was calculated on the basis of following Eqs ( 4 , 5 ) ( Qiang et al., 2017 ) as 1.41×10 5 /mL and 4.23×10 5 /mL, respectively.

where SD is the standard deviation of the frequency response and m is the slope of the regression line. That means, the lowest amount of analyte in a sample which can be detected but not necessarily quantitated as an exact value is 1.41×10 5 /mL, the lowest amount of analyte in a sample which can be quantitatively determined is 4.23×10 5 /mL. This experiment demonstrated that there is a linear relationship between the magnitude of the amplitude under the microwave resonator and the number of cells. Specifically, when the number of cells exceeds a certain threshold (6.4×10 4 /mL), the solution of adherent cells treated with ultrapure water shows this relationship. This experiment confirms that using this microwave sensor to measure cytotoxicity as an endpoint is feasible.

Figure 5 . Results of the pre-experiment on cell number measurement. Cells cultured in DMEM at a concentration of (A) 6.4×10 4 /mL, (B) 1.25×10 4 /mL, (C) 2.5×10 5 /mL, (D) 5×10 5 /mL, (E) 1×10 6 /mL, (F) 2×10 6 /mL. (G) Cells in PBS, and (H) cells in ultrapure water. (I) S 11 of different concentrations in ultrapure water. (J) Linear fitted results of cell concentration and magnitude in resonant frequency.

3.2 Measurements from drug inhibition experiments

The results of the drug concentration cytotoxicity assay measurements are presented in Figure 6 . Figure 6A demonstrates the cell growth after 48 h of culture with drug concentration ranging from 1.7 μM to 12.65 μM. It can be clearly seen that the number of live cells gradually decreased as the drug concentration increased, and the inhibition of cell growth by the drug can be assessed from the number of surviving live cells. The inhibitory capacity of mitomycin reaches its maximum at drug concentrations of approximately 9.5 μM. Higher concentrations have similar inhibitory effects to 9.5 μM. The cells were subjected to OD450 measurements, depicting the curves in Figure 6B . In addition, the curves of cell concentration and OD450 values were measured for HepG2, and the results are shown in Figure 6C which is similar to the results of the OD450 measurement of cell number in Figure 5J . Since OD450 values have a good linear relationship with cell concentration, OD450 measurements can be equated to cell concentration. Microwave resonance peak amplitude measurements were performed after ultrapure water treatment. A set of near-mean measurements was selected and their S 11 are plotted in Figure 6D . It can be observed that the amplitude of the resonance peak decreases by approximately 0.45 dB as the drug concentration increases from 1.70 μM to 12.65 μM. The relationship between amplitude and drug concentration was plotted in Figure 6E after an equal number of measurements were taken in three parallel groups and the mean value was selected. It can be seen that the microwave resonance amplitude measurements have similar results to the OD450 measurements. At higher drug concentrations, the resonance amplitude tends to a stable value. Therefore, it is feasible to use the resonance amplitude curve as an assessment index of drug toxicity. Various in vitro cytotoxicity assays are currently available including chromium release, bioluminescence, impedance, and flow cytometry ( Kiesgen et al., 2021 ), most of which are based on chemical methods such as fluorescent labelling, optical densitometry and radioactivity determination. These methods have their characteristics and scope of application as well as limitations, microwave sensor methods introduce a new possibility for cytotoxicity determination, and their comparison is presented in Table 1 . These methods can be divided into two main categories, optical and electrical, covering a wide range of cellular measurements. In terms of device size, microwave biosensors have the advantage of being small. Microwave methods are on a similar scale to flow cytometry in terms of the concentration of cells that can be processed. Microwave methods are characterized by a tiny sample capacity (0.8 μL∼ 2 μL) in addition to inheriting the advantages of electrical methods that do not require staining of cells.

Figure 6 . Results of cytotoxicity assay for different concentrations of drugs. (A) Microscopic images of cells cultured at different drug concentrations for 48 h and washed with PBS buffer to remove dead cells. (B) OD450 value detection of live cells after 48 h of action with different concentrations of Mitomycin-c. (C) Measurement results of linear relationship between HepG2 concentration and OD450 value. (D) Measurement results of S 11 after drug concentration 1.7 μM∼40.0 μM action. (E) Microwave amplitude detection of living cells in aqueous solutions of Mitomycin-c with different concentrations after 48 h of action.

Table 1 . Summaries of existing cytotoxicity assays.

3.3 Experimental principles

The measurement mechanism of this experiment is divided into two main parts. The first part is cellular water uptake and subsequent rupture as shown in Figure 7A . When a cell is placed in ultrapure water, the concentration of the solution inside the cell is relatively high, while the concentration of the solution in ultrapure water is extremely low. Osmotic forces drive water molecules from the exterior into the cell, causing a volumetric expansion of the cell, a phenomenon termed cellular water absorption. However, if the cell absorbs more water molecules than it can hold, the increased internal pressure may cause the cell membrane to rupture. This typically happens when the cell membrane’s elastic limit is surpassed. After mechanical shaking, the broken cell membrane and various ions within the cell are dispersed relatively uniformly in solution. Differences in the number of cells can lead to differences in the final total ion concentration of the solution, as the cells are treated with equal amounts of ultrapure water. It should be noted that the number of cells should not be too high, otherwise they may not all rupture completely after absorbing water.

Figure 7 . Experimental principles. (A) Cell rupture in ultrapure water. (B) Measurement of sample in biosensor.

The second part is the principle of sample detection by the microwave biosensor as shown in Figure 7B . The cytosol contains a variety of ions, with sodium, potassium and chloride ions making up a large proportion. The effect of ion concentration on dielectric properties has been studied extensively, e.g., an increase in the concentration of sodium chloride leads to a decrease in the loss angle tangent ( Wang et al., 2013 ; Dandan et al., 2015 ). When the concentrations of sodium chloride and potassium chloride solutions are below a certain value, the dielectric properties of the solutions are similar to those of pure water, and only when they are above a certain value do the dielectric properties show a clear trend ( Eldamak et al., 2020 ). The loss angle tangent describes the nature of the ability of a material to absorb electromagnetic waves and is related to the energy loss in the material. As the concentration of a solution increases, so does the number of solute molecules or ions. At lower concentrations, the ions in the solution have a weaker ability to absorb electromagnetic waves, resulting in a larger loss angle tangent. However, as the concentration increases, the polarization effect of the ions in the solution increases, making the solution less able to absorb electromagnetic waves, resulting in a decrease in the loss angle tangent. Changes in the loss angle tangent affect the degree of microwave attenuation in the solution and the resonance peak of the resonator. When the solution is dropped onto the capacitive area of the microwave resonator, the medium surrounding the capacitive area changes, and the microwave biosensor detects this change sensitively and rapidly. The VNA sends a microwave signal over a set frequency range and measures the amplitude and phase of the reflected and transmitted signals. By varying the frequency and recording the corresponding signal response, data on the S 11 can be obtained. Further, the VNA can be connected to a computer to efficiently detect changes in the analyzed parameters using the corresponding software.

4 Conclusion

In this work, a microwave resonant sensor based on an integrated passive device is presented. The device can be used for cell number detection and further, for the assessment of the degree of cell growth inhibition by drug concentration. The sensor’s capability to detect cytotoxicity was validated against the biological gold standard, the CCK-8 assay. Unlike the usual PBS treatment of cells, ultrapure water was used to treat the cells in this experiment, offering an innovative approach for cell sensing via microwave technology. This novel method provides rapid, precise, and miniaturized cytotoxicity assessments, suitable for various applications. Future enhancements should concentrate on minimizing random detection errors through appropriate peripheral matching circuits and improving sensor sensitivity via structural design modifications. The improvement of the device structure relies mainly on the optimization of the interdigital capacitance. The matching of microwave biosensors with electronic circuits and the introduction of algorithms can result in a miniaturized smart device.

Data availability statement

The original contributions presented in the study are included in the article/Supplementary material, further inquiries can be directed to the corresponding authors.

Ethics statement

Ethical approval was not required for the studies on humans in accordance with the local legislation and institutional requirements because only commercially available established cell lines were used. Ethical approval was not required for the studies on animals in accordance with the local legislation and institutional requirements because only commercially available established cell lines were used.

Author contributions

J-MZ: Writing–original draft, Conceptualization, Data curation, Formal Analysis, Investigation, Methodology, Software, Validation, Visualization. Y-KW: Writing–review and editing, Methodology, Software. B-WS: Writing–review and editing, Methodology. Y-XW: Writing–original draft, Validation. Y-FJ: Writing–review and editing, Supervision. G-LY: Writing–review and editing, Supervision. X-DG: Writing–review and editing, Supervision. TQ: Writing–review and editing, Supervision, Conceptualization, Funding acquisition, Project administration, Resources, Visualization.

The author(s) declare that financial support was received for the research, authorship, and/or publication of this article. This research is supported by National Natural Science Foundation of China (Grant No. 61801146), Project funded by China Postdoctoral Science Foundation (Grant No. 2021M691284), Postgraduate Research and Practice Innovation Program of Jiangsu Province (Grant No. SJCX23_1226), and Open Project of the Key Laboratory of Nanodevices and Applications, Chinese Academy of Sciences (Grant No. 22ZS07).

Acknowledgments

The authors acknowledge helpful conversations regarding the interpretation of these data with Prof. Xiaoman Zhou (School of Biotechnology, Jiangnan University, Wuxi, China). The sample of Figure 3 is designed by macrovector/Freepik.

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

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Keywords: cytotoxicity assay, microwave sensors, live cells, drug concentrations, growth inhibition

Citation: Zhao J-M, Wang Y-K, Shi B-W, Wang Y-X, Jiang Y-F, Yang G-L, Gao X-D and Qiang T (2024) Microwave biosensor for the detection of growth inhibition of human liver cancer cells at different concentrations of chemotherapeutic drug. Front. Bioeng. Biotechnol. 12:1398189. doi: 10.3389/fbioe.2024.1398189

Received: 09 March 2024; Accepted: 23 April 2024; Published: 13 May 2024.

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Copyright © 2024 Zhao, Wang, Shi, Wang, Jiang, Yang, Gao and Qiang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Xiao-Dong Gao, [email protected] ; Tian Qiang, [email protected]

This article is part of the Research Topic

Insights in Biosensors and Biomolecular Electronics 2024: Novel Developments, Current Challenges, and Future Perspectives