Smartphone Based Medical Diagnostics

Jeong-Yeol Yoon

• Publisher: Academic Press
• Year: 2019
• ISBN:
  9780128170458
• Topic: Technology & Engineering
• Subtopic: Engineering General
• Index: Technology & Engineering

Smartphone Based Medical Diagnostics provides the theoretical background and practical applications for leveraging the strengths of smartphones toward a host of different diagnostics, including, but not limited to, optical sensing, electrochemical detection, integration with other devices, data processing, data sharing and storage. The book also explores the translational, regulatory and commercialization challenges of smartphone incorporation into point-of-care medical diagnostics and food safety settings.

• Presents the first comprehensive textbook on smartphone based medical diagnostics
• Includes a wide array of practical applications, including glucose monitoring, flow cytometry, rapid kit, microfluidic device, microscope attachment, and basic vital sign/activity monitoring
• Covers translational, regulatory and commercialization issues

Chapter 1

Introduction

Jeong-Yeol Yoon, PhD Professor, Department of Biomedical Engineering and Department of Biosystems Engineering, The University of Arizona, Tucson, AZ, United States

Abstract

Overview of the entire book is addressed in this chapter. A couple of basic terms are defined, including biomedical diagnostics and biosensors. A basic concept of biosensors is then introduced, and two most popular transducers—optical and electrochemical—are briefly explained. The sensors and connectivity options available in many commercial smartphones are explained, and their utilization toward biosensing and ultimately biomedical diagnostics is explained. A brief introduction on the remaining chapters of this book is summarized at the end of this chapter.

Keywords

Biomedical diagnostics; Bioreceptor; Biosensor; Medical diagnostics; Smartphone

Overview of the entire book is addressed in this chapter. A couple of basic terms are defined, including biomedical diagnostics and biosensors. A basic concept of biosensors is then introduced, and two most popular transducers—optical and electrochemical—are briefly explained. The sensors and connectivity options available in many commercial smartphones are explained, and their utilization toward biosensing and ultimately biomedical diagnostics is explained. A brief introduction on the remaining chapters of this book is summarized at the end of this chapter.

1. Some definitions: medical diagnostics and biosensors

The title of this textbook is “Smartphone Based Medical Diagnostics.” Diagnostics, by definition, is the discipline (like mathematics) of diagnosis. Diagnostics is sometimes abbreviated Dx. Diagnosis, by definition, is the identification of the nature and/or cause of a certain phenomenon. It is sometimes abbreviated Ds. In medical diagnostics, the phenomenon is typically a disease, disorder, and/or syndrome in a human subject. The nature and cause of disease, disorder, or syndrome vary substantially, ranging from pathogens (including bacteria, viruses, and fungi), toxic chemicals, cancer, genetic disorder, and traumatic injury, to name a few. Medical diagnostics can be expanded to biomedical diagnostics, to include the phenomena occurring in nonhuman subjects, such as plants, animals, food, water, and air, all of which can eventually affect human health.

In a traditional sense, medical and biomedical diagnostics should be performed in a wet laboratory, where skilled and trained personnel conduct a series of sample (mostly liquid) handling procedures using a variety of analytical instruments. Such laboratory-based medical diagnoses have been replaced with standalone biosensors in the past couple of decades, greatly reducing the cost and time of such diagnoses, as well as allowing the diagnosis to be performed not in a remote laboratory, but at the point of care (called as POC diagnostics or POC Dx), or even at the convenience of patient's own home [1].

Figure 1.1 Three most popular commercial biosensors. Top left: a glucose meter (with a glucose strip inserted) is measuring blood glucose concentration from a finger prick blood sample. Top right: a pregnancy test is evaluating a pregnancy hormone (hCG) from urine sample. Bottom: a pulse oximeter is measuring pulse and blood oxygen saturation from a human finger.
Top left: Reprinted from Ref. [1] with permission, (C) 2016 Springer. Top right: Reprinted from Ref. [2]. Bottom: Reprinted from Ref. [3].

At the time of writing, three biosensors have been most successfully commercialized and are widely used at hospitals, doctor's offices, and homes—glucose meter, pregnancy test, and pulse oximeter (Fig. 1.1) [1–3]. In all three cases, the biosensors are detecting targets whose concentrations are very high—glucose in blood, pregnancy hormone (human chorionic gonadotropin or hCG) in urine, and hemoglobin in blood—and can be detected relatively easily. Of course, many other biosensors are also available commercially and new types of biosensors are continuously emerging at this time, often targeting the molecules whose concentrations are substantially lower than those listed above.

2. What is biosensor?

Biosensor is one type of sensor that can identify the type/species and/or the concentration of biological analyte. Examples of bioanalytes include a simple biochemical compound (e.g., glucose), a sequence of nucleic acid (DNA or RNA), a specific protein, a virus particle, a bacterium, and so on [1]. The presence of these biological analytes and/or their concentrations can then be utilized to identify the nature and cause of disease, disorder, or syndrome. Therefore, biosensors are mostly used for biomedical diagnostics.

Figure 1.2 A typical biosensor.

To identify and quantify these bioanalytes, bioreceptors are necessary (Fig. 1.2). Bioreceptors bind to the target analytes in a highly specific manner. Obviously, a wide variety of bioreceptors have been tested and evaluated for biosensors and subsequently medical diagnostics. The following two types of bioreceptors have been used most frequently: (1) antibodies and (2) enzymes. Antibodies are protein molecules normally found in human (as well as animal) blood. They bind to the target antigens and thus nullify the antigen's action in the body—hence they form a part of human's (as well as animal's) immune system. They are relatively specific, for example, antibody to the well-known bacterium Escherichia coli (i.e., anti-E. coli) binds only to E. coli but not to other bacteria, viruses, or proteins. (In reality, anti-E. coli can also bind to the other bacteria that are similar to E. coli, called as cross-binding; however, such probability is relatively low and its specificity is still substantially superior to other chemical ligands.) The target antigens are typically proteins. When antibodies bind to bacteria or viruses, they actually bind to their surface proteins. Enzymes are also protein molecules found in human (or animal) bodies. They bind to the target substrate and catalyze a chemical reaction (most commonly oxidation) of that substrate. Therefore, enzymes are often called as biological catalysts. Substrates are typically small chemical compounds, for example, glucose, cholesterol, alcohol, etc. In addition, enzymes are relatively specific to the target substrate, similar to antibodies.

Once bioreceptor specifically binds to the target bioanalytes, it becomes necessary to quantify the extent of such binding. Such quantifications are performed by transducers (Fig. 1.2). Transducer, in fact, is a pivotal component not just in biosensors but also in all sensors, where the type and concentration of bioanalytes (in biosensors) or the physical property (in sensors) are converted into analog voltage signals, which are further converted to digital signals.

Although other types of transducers are available for biosensors (e.g., piezoelectric and thermal), the following two types are the most commonly used: optical and electrochemical. Biosensors with optical transducers are typically called as optical biosensors and those with electrochemical transducers as electrochemical biosensors. Both types of biosensors are explained in Chapter 2 and Chapter 3.

Both optical and electrochemical biosensing can be performed using analytical instruments in a wet laboratory. Optical biosensing is conducted typically using a spectrophotometer, and electrochemical biosensing using electrodes (e.g., pH, ion-selective, or conductivity electrode) or an impedance analyzer. Commercial optical or electrochemical biosensors are typically simplified versions of such analytical instruments, tailored for a specific application. The major downside of this approach is that each application needs a specific biosensor device, while analytical instruments can be used for multiple (or even general) applications.

As implied in the title of this book, it is also possible to conduct optical and electrochemical biosensing using a smartphone. Considering the widespread availability of smartphones, this approach will certainly reduce the effort and cost of developing a specific biosensor, reduce the actual cost of assays, and allow the general public to familiarize themselves to new biosensor technology. In addition, smartphones carry advanced processing units (their computing power far outperforming those incorporated in commercial biosensors), a large amount of memory for data storage, and ability to send the raw and processed assay results to a cloud storage and/or other mobile device. These features are not possible with commercial biosensors, unless a separate laptop computer (which severely compromises the portability of the biosensor) is connected to them.

3. What sensors are available in smartphones for biosensing?

Before the era of smartphone, cellular phones (or mobile phones) were also equipped with a couple of extra features other than voice calls, including text messaging and limited data networking capabilities. To make a distinction from modern smartphones, such cellular (or mobile) phones are retroactively called as feature phones. In fact, digital data transmission has made possible with 2G (second generation) cellular technology, where voice, text, and data are all transmitted in digitally encrypted fashion. (In comparison, the 1G cellular technology wa...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributors
• Chapter 1. Introduction
• Chapter 2. Basic principles of optical biosensing using a smartphone
• Chapter 3. Basic principles of electrochemical biosensing using a smartphone
• Chapter 4. Smartphone for glucose monitoring
• Chapter 5. Smartphone-based flow cytometry
• Chapter 6. Smartphones for rapid kits
• Chapter 7. Smartphone-based medical diagnostics with microfluidic devices
• Chapter 8. Digital health for monitoring and managing hard-to-heal wounds
• Chapter 9. Smartphone-based microscopes
• Chapter 10. Smartphone for monitoring basic vital signs: miniaturized, near-field communication based devices for chronic recording of health
• Chapter 11. Food safety applications
• Index