Disposable Electrochemical Sensors for Healthcare Monitoring

Material Properties and Design

A Pandikumar, K S Shalini Devi, A Pandikumar, K S Shalini Devi

• Publisher: Royal Society of Chemistry
• Year: 2021
• Edition: 1
• eBook ISBN:
  9781839163371
• Topic: Physical Sciences
• Subtopic: Analytic Chemistry

Disposable electrodes have been widely used as a sensing platform in electrical and electrochemical sensors owing to the possibility of quantitative detection using clinical biomarkers with high precision, sensitivity and reproducibility, which are necessary for accurate diagnosis of the health condition of an individual. This book focusses on the emerging disposable electrochemical sensors in the health sector and the advancement of analytical devices to monitor diabetic, cancer and cardiovascular patients using different nanomaterials. It discusses the upcoming strategies, advantages and the limitations of the existing devices using disposable electrodes. Uniquely, it covers in-depth knowledge of mechanistic features of various designs of screen-printing electrodes and the material aspects required of sensors developed for the healthcare field. It also looks at the portable devices using a variety of materials and the future directions for research in this area.
Appealing to the health care industry, this book is aimed at academic and research institutes at both the graduate and postgraduate level. The contributors are leading experts in the field and they are providing guidance for the next decade of research in the field of disposable electrochemical biosensors.

CHAPTER 1

The Design and Fabrication of Disposable Sensors: an Overview

RAJENDRAN RAJARAM^*a, ^*b AND JAYARAMAN MATHIYARASU^c

^a Department of Chemistry, Indian Institute of Technology Madras, Chennai – 600036, Tamil Nadu, India

^b Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai – 600036, Tamil Nadu, India,
^*E-mail: [email protected]

^c Electrodics and Electrocatalysis Division, CSIR-Central Electrochemical Research Institute, Karaikudi – 630 003, Tamil Nadu, India

This chapter starts with a brief introduction about biosensors, their basic characteristics and differentiates the term biosensors from sensors. Further, it focuses on electrochemical biosensors, the type of sensors and provides the theoretical background, working principles, types and advantages, role of macro and disposable electrodes in biosensors and their modification. Applications of disposable electrodes in various fields, including healthcare, agriculture, environment are discussed. The necessity of the detection of the analytes and the consequences of their presence in excess/absence in living systems and in the environment is also discussed.

1.1 Introduction

Biosensors are devices that are used to quantify the presence or concentration of bioanalyte(s) (viz., biomolecules, biological structures, microorganisms etc.) Usually, such devices contain immobilized biomaterials (enzymes, antibodies, nucleic acids, hormones, organelles or whole cells), transistor components and electronic systems such as signal amplifiers, processors and displays. The immobilized bioreceptors selectively interact with a bioanalyte of interest and the reaction takes place. The reaction is measured using biotransducers that produce measurable physical, chemical or electrical signals. There are a number of biosensors for the detection of various analytes including glucose, lactate, pyruvate, cholesterol, ethanol, creatinine, glutamate, choline and acetylcholine. They have applications in various fields such as healthcare, food, industrial and environmental. ^1,2 According to IUPAC, biosensors are defined as devices capable of providing quantitative/semi-quantitative information using biological recognition. ^3,5 The role of these biosensors are effective in various fields and particularly in healthcare applications such as monitoring, screening of diseases, pollution control, environmental monitoring etc. ^3,6,7

However, some of the devices are classified as sensors, which are slightly different from biosensors. They are able to produce an output with respect to its specific physical quantity (input) (or) they can convert signals from energy to electrical in the absence of any biomaterial. Some of the common sensor examples are temperature, humidity, light, colour, etc. These are helpful in environmental applications and energy conversion applications. ^8,16 However, they are less common in healthcare applications.

The major difference between sensors and biosensors is: (i) sensors are able to produce a signal according to the concentration of a specific compound in a complex system whereas, (ii) biosensors use biologically derived components for the transduction process. (e.g. enzyme electrodes). Recently, however, the term ‘biosensor’ has been applied to any sensor that can measure the chemical concentration of a biological system. ¹⁷

1.2 The Basic Characteristics of a Biosensor

For a matrix to become a successful electrochemical biosensor, it should obey all the required characteristics of a biosensor which are discussed below.

1.2.1 Linearity

A biosensor should have a wide linear range for the detection of high substrate concentration.

1.2.2 Sensitivity

Sensitivity can be defined as the value of the electrode response per substrate concentration. It should be greater for a better electrochemical biosensor.

1.2.3 Selectivity

An electrochemical biosensor should yield signal selectively for a single analyte. Interference from foreign molecules other than the required bioanalyte must be avoided/minimized to obtain a reliable result.

1.2.4 Response Time

This is the time requirement of a matrix for having 95% of the response. It should be as low as possible to produce a faster response.

1.3 Electrochemical Biosensors and Their Working Principle

There are a number of analytical tools such as chromatographic methods, spectroscopic analysis, and luminescence available. However, these involve discrete sampling followed by laboratory analysis. These are expensive, time consuming and does not provide high-resolution data. However, electrochemical measurements provide excellent sensitivity and selectivity, continuous reliability and portability. Therefore, they are identified as superior analytical tools. ^18,21

The desired biomolecules such as enzyme, hormones, antibodies etc. are immobilized via physisorption/chemisorption, which will cause an intimate contact with the transducer. The analyte of interest will selectively bind with the biomaterial that produces the measurable electronic response (Figure 1.1).

Figure 1.1 Schematic representation of working principle of electrochemical biosensors.

Based on working principles, electrochemical sensors are classified as follows:

• Potentiometric biosensors
• Amperometric biosensors
• Conductometric biosensors
• Impedemetric biosensors
• Piezoelectric biosensors.

1.3.1 Potentiometric Biosensors

Potentiometric biosensors are traditional sensors used to determine the concentration of the analyte molecule. Ion-selective electrodes are the best examples of potentiometric biosensors. They function based on the working principle of a galvanic cell, which consists of a reference electrode, ion-selective membrane and a voltmeter. The composition of the membrane is designed to produce the potential with respect to the ion of interest. As a result, selectivity can be achieved. The driving force for the analysis is the movement of ions towards the specific site of a membrane due to a concentration gradient. This phenomenon of mobility of ions leads to a potential difference during the analysis. This potential is measured with a standard reference electrode. The difference depends on the activity of a particular ion. The most common potentiometric device is a pH meter. Potentiometric biosensors are also used to transduce a biological reaction into an electrical signal. They are able to produce signals in the concentration range of 10⁻⁸ to 10⁻¹¹ M. The signal is measured at zero current. These biosensors have an enzyme membrane that surrounds the probe from a pH meter.

The equilibrium potential of the electrode can be related to the concentration of the analyte, which is governed by the Nernst equation (eqn (1.1)):

1.1 E _eq = E° + (2.303 RT/nF) log [M ⁿ⁺ ]

where E _eq is the equilibrium electrode potential, E° is the standard electrode potential, n is the number of electrons involved in the reaction, M ↔ M ⁿ⁺ + ne⁻, [M] is the activity of the analyte ion in the solution, R is the gas constant, T is the temperature in Kelvin and F is the Faraday constant (96 485 coulombs). Since, E°, R, T, n and F are constants, the activity coefficient is also kept constant (eqn (1.2)).

1.2 E _eq α log C _M ⁿ⁺

Therefore, potentiometric sensors are very attractive for field operations because of their high selectivity, simplicity and low-cost methods to determine the ionic concentration through potential difference measurements. pH electrodes and other various ion-selective electrodes are examples for potentiometric sensors. ^22,24 ...

Table of contents

• Cover
• Series
• Title
• Copyright
• Biographies
• Preface
• Contents
• Chapter 1 The Design and Fabrication of Disposable Sensors: an Overview 1
• Chapter 2 Carbon Nanotubes Chemically-modified Screen-printed Electrodes Electrochemical Platforms for Biomedical Applications 27
• Chapter 3 Mesoporous Carbon-based Disposable Sensors 79
• Chapter 4 Graphene-based Disposable Sensors 103
• Chapter 5 Graphitic Material-based Disposable Sensors 125
• Chapter 6 Metal Nanoparticles-based Disposable Sensors 170
• Chapter 7 Metal Oxide-based Disposable Sensors for Health Monitoring 204
• Chapter 8 Metal–Organic Framework-based Disposable Sensors 232
• Chapter 9 Metal Chalcogenides-based Disposable Sensors 265
• Chapter 10 Conducting Polymer-based Disposable Sensors 284
• Chapter 11 Quantum Dots-based Disposable Sensors 314
• Chapter 12 Mxene-based Disposable Sensors 353
• Chapter 13 Functionalized Macromolecules-based Disposable Sensors 381
• Chapter 14 Existing Point-of-care Diagnostics: Merits and Demerits 410
• Chapter 15 Future Perspectives of Disposable Electrochemical Sensors 432