Biosensors

Introduction

A biosensor is a device for the detection of an analyte that combines a biological component with a physicochemical detector component. It should be able to convert a biological response into an electrical signal.

Biosensors represent a rapidly expanding field, at the present time, with an estimated 60% annual growth rate; the major impetus coming from the health-care industry (e.g. 6% of the western world are diabetic and would benefit from the availability of a rapid, accurate and simple biosensor for glucose) but with some pressure from other areas, such as food quality appraisal

and environmental monitoring.

Component of biosensors

It consists of 3 parts:

1. The sensitive biological element (eg. tissue, microorganisms, organelles, cell receptors, enzymes, antibodies, nucleic acids, etc).

2. The transducer or the detector element.

3. Associated electronics or signal processors.

Features of a successful biosensor

1. It must be highly specific for the purpose.

2. It should be stable under normal storage conditions.

3. It must have a good stability over a large number of assays.

4. The reaction should be independent from other physical parameters such as pH and temperature.

5. The response should be accurate, precise, reproducible and linear over the useful analytical range.

6. It should be cheap, small and portable.

7. It should be capable of being used by a semi-skilled person.

Types of biosensors

There are different types of biosensors are available such as Electrochemical, Piezoelectric, and Thermometric and Optical biosensors in the analytical field.

Electrochemical Biosensors

An electrochemical biosensor is a self-contained integrated device, which is capable of providing specific quantitative or semi-quantitative analytical information using a biological recognition element (biochemical receptor) which is retained in direct spatial contact with an electrochemical transduction element.

Piezoelectric biosensor

The development of a piezoelectric biosensor based on nucleic acids interaction is presented focusing on the methodology for probe immobilization. This is a key step in any DNA biosensor development. Often, the detection limits and, in general, the analytical performances of the biosensor can be improved by optimizing the immobilization of the receptor on the transducer surface.

Thermometric biosensors

Thermometric biosensors are constructed by combining enzymes with temperature sensors. When the analyte is exposed to the enzyme, the heat of reaction of the enzyme is measured and is calibrated against the analyte concentration.

Optical biosensors

Optical Biosensors provides the most comprehensive analysis of optical biosensors and relevant technologies to date. According to the optical configuration, optical sensors have classified into two modes. When light is reflected at an optical interface where there is a change of refractive index, there is a decay of energy from the point of reflection into the surrounding medium. This energy field which extends into the medium depends upon the medium in which the wave guide is dipped. The resultant changes of luminescence, absorption or fluorescence can hence be determined. When the glass surface of the biosensor is coated with a thin layer of metal (silver, gold), the intensity of the resonance angle changes depending on the concentration of the medium in which electrode is immersed. This phenomenon is called the surface plasma resonance (SPR).

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Applications of biosensors

biosensors in food analysis

biosensors and forensic medicine