Medical Biosensors for Point of Care (POC) Applications

Roger Narayan, Roger J Narayan

• Publisher: Woodhead Publishing
• Year: 2016
• Print ISBN: 9780081000724
• eBook ISBN: 9780081000786
• Topic: Medicine
• Subtopic: Medical Technology & Supplies

Medical Biosensors for Point of Care (POC) Applications discusses advances in this important and emerging field which has the potential to transform patient diagnosis and care. Part 1 covers the fundamentals of medical biosensors for point-of-care applications. Chapters in part 2 go on to look at materials and fabrication of medical biosensors while the next part looks at different technologies and operational techniques. The final set of chapters provide an overview of the current applications of this technology. Traditionally medical diagnostics have been dependent on sophisticated technologies which only trained professionals were able to operate. Recent research has focused on creating point-of-care diagnostic tools. These biosensors are miniaturised, portable, and are designed to be used at the point-of-care by untrained individuals, providing real-time and remote health monitoring. - Provides essential knowledge for designers and manufacturers of biosensors for point-of-care applications - Provides comprehensive coverage of the fundamentals, materials, technologies, and applications of medical biosensors for point-of-care applications - Includes contributions from leading international researchers with extensive experience in developing medical biosensors - Discusses advances in this important and emerging field which has the potential to transform patient diagnosis and care

Part One

Fundamentals of medical biosensors for POC applications

Outline

1. Introduction to medical biosensors for point of care applications

2. Validation and regulation of point of care devices for medical applications

3. Materials for improved point of care biosensor–tissue interfaces

1

Introduction to medical biosensors for point of care applications

K. Baryeh, S. Takalkar, M. Lund, and G. Liu North Dakota State University, Fargo, ND, United States

Abstract

On a global scale, high mortality rates of various infectious diseases and cancers are symptomatic of inadequate diagnostic tools because of high cost of, and poor access to, medical care. The available assays at the moment may suffer from poor sensitivity, selectivity, as well as being time-consuming. Therefore, a large demand exists for the development of an efficient device that provides sensitive and selective results for early detection of said diseases, thus improving prognosis as well as lowering the mortality rate. Scientists have developed various medical biosensors which seek to address the aforementioned shortcomings. This chapter is an introduction to medical biosensors, but, more specifically, to point-of care (POC) biosensors. POC biosensors allow for the sensitive, selective, and rapid detection of diseases while remaining inexpensive. In this chapter, the general working principle of the POC device is presented including which POC devices have already been manufactured for commercial use.

Keywords

Antibodies; Biorecognition; Blood-glucose biosensor; Lab-on-chip; Medical biosensors; Miniaturized devices; Point-of-care; Testing

1.1. Biosensors and medical biosensors

A biosensor is a self-contained integrated device capable of providing specific quantitative or semiquantitative analytical information using a biological recognition element which is in direct spatial contact with a transducer element⁸³. Fig. 1.1 presents the basic scheme of a biosensor. It consists of three parts: the sensitive biological element, the transducer, and the associated electronics or signal processors that are primarily responsible for the display of the results in a user-friendly way. The biological recognition element plays a vitally important role because it determines the specificity of the biosensor. The biorecognition events can be recognized by various transducers to produce a signal (optical, electrochemical, and piezoelectric) proportional to a single analyte which is then conveyed to a detector. Biosensor research and development has been an area of increased research interest for over the last half-century. The first medical biosensor, an enzyme electrode for oxygen sensing, was reported by Professor Clark at the New York Academy of Science in 1962,¹ and was utilized for the continuous monitoring of oxygen levels in blood during cardiovascular surgery. Since then, there have been numerous advances in the field of biosensors drawing expertise from physics, chemistry, biochemistry, as well as engineering.² Biosensors have wide applications in the medical field for the detection of cancer, genetic disorders, and pathogens alike. The most widespread example of a commercial biosensor is the blood-glucose biosensor. These are known as medical biosensors and seek to increase the sensitivity, selectivity, and reliability of the biosensors, while reducing the time for sampling and the acquisition of test results. With the improvement in these areas, medical biosensors could become an essential tool in the field of medicine. Therefore, research is gearing toward miniaturizing and simplifying these for use in home-based preliminary screening.

1.2. Biosensors for point of care testing

One of the most important applications of biosensors is the point of care testing (POCT). POCT is the practice of performing a diagnostic or prognostic test near the patient to provide rapid results, meaning that the test itself has to be quick and easily performed without the use of expensive or complicated instrumentation. It also means that samples do not require the attention of any skilled technician as there is no need of the laboratory analysis, as well as no wait time for the collection and analysis of the results.^4,5 The person who is conducting the test (doctor, nurse, or the patients themselves) initiates the test and receives results on the spot, thus saving time. The POCTs are feasible in various environments; in general, these are the practitioner’s surgery, hospital clinic, hospital ward, emergency room, intensive care unit, or even a patient’s home. The need for sensitive, robust, portable, and inexpensive biosensor platforms is of significant interest in clinical applications for disease diagnosis and treatment monitoring at the point of care (POC) settings. In developing countries with constraints such as limited laboratory infrastructure, nonavailability of trained personnel, and—the major reason—lack of financial support, POC diagnostic assays play a crucial role. Millions die each year in the populated countries like India and China due to infectious diseases like malaria, AIDS, and tuberculosis. These developing countries are still struggling for access to treatment options available in developed countries.^6,7

Figure 1.1 Basic scheme of a biosensor.³

Accurate and early diagnoses play a crucial role in identifying the actual cause and nature of any disease. Currently, the emphasis and major focus are being shifted toward the early detection of a disease to effectively manage the treatments, thus reducing the mortality rates among patients. POCT and its ability to generate immediate results in nonlaboratory settings supports more patient-centered approaches for health-care delivery and is a prospect in the field of early detection.

1.3. Biorecognition elements of medical biosensors

The utility of any biosensor relies centrally on its ability to distinguish the target analyte from interfering molecules. As such, various biorecognition elements including antibodies, nucleic acids, cells, bacteriophages, and proteins have been employed by researchers over the years. This section seeks to review these biorecognition elements and show the strengths of each.

1.3.1. Antibodies

Traditionally, antibodies have been the main biorecognition elements used. Antibodies have been applied in various biosensor platforms including electrochemical,⁸ fluorescent,^9,10 and colorimetric assays.¹¹ Antibodies provide varying stringency of interactions depending on whether they are monoclonal or polyclonal. Monoclonal antibodies have the advantage of recognizing a single epitope of a target molecule, whereas polyclonal antibodies will recognize different epitopes of the same target. Because monoclonal antibodies are specific to a single epitope, they are less prone to cross-reactivity than polyclonals; however, the cost of production of polyclonals is more economical so polyclonals are still used. The most important application of the antibody-based biosensors is the development of immunochromatographic test strips for POCTs. The detailed POC applications of immunochromatographic test strips will be discussed in Section 1.4. However, antibodies as a whole suffer some drawbacks that limit their POC applications, namely they are relatively expensive to produce and must be stored under controlled low-temperature conditions. When not stored properly they denature and lose their binding ability which limits their utility in making assays for infield applications. This can be a big problem in poor communities with erratic power supply where continued refrigeration is not feasible. As a resul...

Table of contents

• Cover image
• Title page
• Table of Contents
• Related titles
• Copyright
• List of contributors
• Woodhead Publishing Series in Biomaterials
• Part One. Fundamentals of medical biosensors for POC applications
• Part Two. Materials, fabrication and types of biosensors for POC applications
• Part Three. POC biosensors for particular clinical applications
• Index