Molecular Sensors and Nanodevices

Principles, Designs and Applications in Biomedical Engineering

John X. J. Zhang, Kazunori Hoshino

• Publisher: William Andrew
• Year: 2013
• eBook ISBN: 9781455776764
• Topic: Biological Sciences
• Subtopic: Biotechnology
• Index: Biological Sciences

With applications ranging from medical diagnostics to environmental monitoring, molecular sensors (also known as biosensors, chemical sensors, or chemosensors), along with emerging nanotechnologies offer not only valuable tools but also unlimited possibilities for engineers and scientists to explore the world. New generation of functional microsystems can be designed to provide a variety of small scale sensing, imaging and manipulation techniques to the fundamental building blocks of materials. This book provides comprehensive coverage of the current and emerging technologies of molecular sensing, explaining the principles of molecular sensor design and assessing the sensor types currently available. Having explained the basic sensor structures and sensing principles, the authors proceed to explain the role of nano/micro fabrication techniques in molecular sensors, including MEMS, BioMEMS, MicroTAS among others. The miniaturization of versatile molecular sensors opens up a new design paradigm and a range of novel biotechnologies, which is illustrated through case studies of groundbreaking applications in the life sciences and elsewhere. As well as the techniques and devices themselves, the authors also cover the critical issues of implantability, biocompatibility and the regulatory framework. The book is aimed at a broad audience of engineering professionals, life scientists and students working in the multidisciplinary area of biomedical engineering. It explains essential principles of electrical, chemical, optical and mechanical engineering as well as biomedical science, intended for readers with a variety of scientific backgrounds. In addition, it will be valuable for medical professionals and researchers. An online tutorial developed by the authors provides learning reinforcement for students and professionals alike.- Reviews of state-of-the-art molecular sensors and nanotechnologies- Explains principles of sensors and fundamental theories with homework problems at the end of each chapter to facilitate learning- Demystifies the vertical integration from nanomaterials to devices design- Covers practical applications the recent progress in state-of-the-art sensor technologies- Includes case studies of important commercial products- Covers the critical issues of implantability, biocompatibility and the regulatory framework

Chapter 1

Introduction to Molecular Sensors

Molecular sensors are devices that detect, record, and indicate a physical or chemical property, with potential capability for further processing and have a sensitivity and specificity at molecular scales. Key sensing components or the design of many molecular sensors are based on those found in living organisms; natural systems are the original form of molecular sensors. Modern sensor technology may not as sophisticated as those found in nature, but it is improving rapidly with the convergence of information technology, breakthroughs in physical design, and advanced manufacturing.

Modern molecular sensors are essential parts of many emerging medical diagnostic devices playing significant roles in global health, reducing healthcare costs in developed countries, and in increasing the response of the world to pandemics or bioterrorism. Prominent areas of molecular sensor research are the detection of biomolecules for disease diagnosis, the detection of volatile components for air pollutant characterization, and the detection of chemical analytes for evaluation of physiological activity.

First we describe the actual composition of molecular sensors.

A sensor is composed of the three main elements: 1. detector (capture and recognition), 2. transducer (signal transduction), and 3. processor.

Molecular sensors employ a variety of capture and recognition mechanisms. For biological molecules, we can use proteins (antibodies, receptors), nucleotides (DNA, RNA, aptamers), synthetic polymers that simulate a binding site, and phages.

Through signal transductions, sensors convert the detection event into a measurable signal. Sensors convert a biological, chemical or physical quantity into a detectable signal, mostly an electrical signal. We categorize molecular sensors into three categories based on the transduction principle: electrical transduction, mechanical transduction, and optical transduction.

Finally, we look at nature’s natural biosensors by examining the olfactory systems of animals and insects and discuss their applications as molecular sensors.

Keywords

molecular sensor; biosensor; chemical sensor; transducer; DNA; RNA; antigen; antibody; thermal noise

Chapter Outline

1.1 Introduction

1.2 Principles of Molecular Sensors

1.2.1 Definition of Molecular Sensors

1.2.2 Applications of Molecular Sensors

1.2.3 Model of a Molecular Sensor

1.2.4 Example of Molecular Sensor 1: Immunosensor Based on Field Effect Transistor

1.2.5 Example of Molecular Sensor 2: Animal Olfactory System

1.3 Capture and Recognition Elements in Molecular Sensors

1.3.1 Antibody–Antigen Binding

1.3.2 DNA as a Recognition Element

1.3.3 Aptamers

1.4 Transduction Mechanisms

1.4.1 Electrical Transduction

1.4.2 Sensitivity of a Transducer

1.5 Performance of Molecular Sensors

1.6 Animals as Molecular Sensors

1.6.1 Sensitivity of Animal Olfactory Systems

1.6.2 Applications of Animal Molecular Sensors

1.6.3 Discussion on Animals as Molecular Sensors

1.7 Conclusion

Problems

P1.1–P1.15

References

Further Reading

1.1 Introduction

Sensors act as interfaces that receive and translate information across physical, chemical, and biological domains. Molecular sensors measure the physical, chemical, and biological quantities at small scales, such as concentration of ions or proteins, existence of toxic molecules, and genetic information from cells, with a sensitivity and specificity at molecular scales. The purpose of this book is to provide comprehensive coverage of current and emerging technologies of molecular sensing, explaining the principles of molecular sensor design and assessing the sensor types currently available for different applications. We will discuss the theories and roles of molecular sensors in light of the development of new materials and fabrication technologies. We also discuss the role of nano/microfabrication techniques in designing and creating molecular sensors. The miniaturization of versatile molecular sensors opens up a new range of nanoscale sensing technology.

Key sensing components or the design of many molecular sensors are based on those found in living organisms. Living organisms have wonderful machinery that contains specialized sensors designed to detect a broad range of molecules, such as toxins and nutrients in the external environment, biomolecular interactions, metabolic activities, glucose levels, and hormones for the internal environment. These natural systems are the original form of “molecular sensors”, which combine biomolecular recognitions with special forms of reporters so that the presence of guests can be “felt” by the organism. These original molecular sensors are the key biotechnologies that enable life to be sustainable, robust and adaptive. Some of the sensor technologies today may not offer the level of sophistication and form factor found easily in nature, but it is improving rapidly with the convergence of information technology, breakthrough of physical design, and advanced manufacturing. These revolutions change the way people live every day. The requirement for molecular sensors in which molecules interact with an analyte to produce a detectable change, is becoming more demanding. Molecular sensors have been used in a large variety of applications. Modern molecular sensors are essential parts of many emerging medical diagnostic devices, which play significant roles in global health, reducing healthcare costs in developed countries, and in increasing the response of the world to pandemics or bioterrorism.

Prominent areas of molecular sensor research are the detection of biomolecules for disease diagnosis, the detection of volatile components for air pollutant characterization, and the detection of chemical analytes for evaluation of physiological activity. Molecular sensors are used in diagnostics, such as glucose monitoring in diabetes patients, body fluids screening for disease detection, and in measurement of other physical parameters such as temperature and pressure. They are used in biomedical R&D in drug discovery and evaluation, and protein engineering. Sensors are used in environmental applications such as water quality detection, air pollution monitoring, detection of pathogens, and gas monitoring. Sensors are also used in food safety, such as the detection of contaminants in drinking water, allergens, and the determination of drug residues. Recent trends in both scientific research and business development indicate a growing interest in molecular sensors with the ultimate goal of developing a broad range of inexpensive, batch-fabricated, high-performance biomedical microdevices, and intelligent platforms, which are easily interfaced with digital electronics for biomedical diagnostics and therapy.

We define the functions and structures of traditional and state of the art molecular sensors, and discuss details of applied areas, including the background and sensing requirements for the application. For each type of sensor we will describe fundamental concepts, theories and practical implementation methods.

1.2 Principles of Molecular Sensors

We start from the definition of molecular sensors, and will introduce fundamental concepts of the molecular sensor, the capture and recognition mechanism, and the sensor signal transduction, followed by description of applications and performances of molecular sensors.

1.2.1 Definition of Molecular Sensors

Sensors are devices that detect, record, and indicate a physical or chemical property, with potential capability for further processing. In this book, we mostly describe molecular sensors, which are designed to quantify the amount of molecules associated with gas, ions, proteins, DNA, and live cells. Although the terms chemical sensors or biosensors are sometimes used almost interchangeably, molecular sensors are considered chemical sensors that are able to detect molecules of interest, or analytes, which are often present at very low concentrations. Some types of physical sensor...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Dedication
• About the Authors
• Preface
• Acknowledgement
• Chapter 1. Introduction to Molecular Sensors
• Chapter 2. Fundamentals of Nano/Microfabrication and Effect of Scaling
• Chapter 3. Microfluidics and Micro Total Analytical Systems
• Chapter 4. Electrical Transducers: Electrochemical Sensors and Semiconductor Molecular Sensors
• Chapter 5. Optical Transducers: Optical Molecular Sensors and Optical Spectroscopy
• Chapter 6. Mechanical Transducers: Cantilevers, Acoustic Wave Sensors, and Thermal Sensors
• Chapter 7. Implantable Sensors
• Appendix 5A. Fresnel Diffraction and Fraunhofer Diffraction
• Appendix 5B. Coupling Between the Evanescent Wave and the Surface Plasmon
• Appendix 6A. Analysis of Beam Bending
• Index