A biosensor is a device for the detection of an analyte that combines a biological component with a physicochemical detector component. An Analyte is the substance or chemical constituent that is undergoing analysis. ...

It consists of 3 parts:

• the sensitive biological element (biological material (eg. tissue, microorganisms, organelles, cell receptors, enzymes, antibodies, nucleic acids, etc), a biologically derived material or biomimic) The sensitive elements can be created by biological engineering.
• the transducer in between (associates both components)
• the detector element (works in a physicochemical way; optical, piezoelectric electrochemical, thermometric, or magnetic.)

The most widespread example of a commercial biosensor is the blood glucose biosensor, which uses an enzyme to break blood glucose down. In doing so it transfers an electron to an electrode and this is converted into a measure of blood glucose concentration. The high market demand for such sensors has fueled development of associated sensor technologies. Biological engineering (a. ...

Recently, arrays of many different detector molecules have been applied in so called electronic nose devices, where the pattern of response from the detectors is used to fingerprint a substance. Machine olfaction is the automated simulation of the sense of smell. ...

A canary in a cage, as used by miners to warn of gas could be considered a biosensor. Many of today's biosensor applications are similar, in that they use organisms which respond to toxic substances at a much lower level than us to warn us of their presence. Such devices can be used both in environmental monitoring and in water treatment facilities. Toxic redirects here, but this is also the name of a song by Britney Spears; see Toxic (song) Look up toxic and toxicity in Wiktionary, the free dictionary. ...

Principles of Detection

Piezoelectric biosensors and optical biosensors based on the phenomenon of surface plasmon resonance are both evanescent wave techniques. This utilises a property shown of gold and other materials; specifically that a thin layer of gold on a high refractive index glass surface can absorb laser light, producing electron waves (surface plasmons) on the gold surface. This occurs only at a specific angle and wavelength of incident light and is highly dependent on the surface of the gold, such that binding of a target analyte to a receptor on the gold surface produces a measurable signal. Piezoelectricity is the ability of certain crystals to produce a voltage when subjected to mechanical stress. ... Surface plasmon resonance, or SPR, is a biophysical technique used by biochemists to measure the binding interactions of very small amounts of a target protein. ... An evanescent wave is an electromagnetic wave that decays exponentially with distance. ... General Name, Symbol, Number gold, Au, 79 Chemical series transition metals Group, Period, Block 11, 6, d Appearance metallic yellow Atomic mass 196. ...

Other optical biosensors are mainly based on changes in absorbance or fluorescence of an appropriate indicator compound.

Piezoelectric sensors utilise crystals which undergo a phase transformation when an electrical current is applied to them. An alternating current (A.C.) produces a standing wave in the crystal at a characteristic frequency. This frequency is highly dependent on the surface properties of the crystal, such that if a crystal is coated with a biological recognition element the binding of a (large) target analyte to a receptor will produce a change in the resonant frequency, which gives a binding signal. In physics, a phase transition, (or phase change) is the transformation of a thermodynamic system from one phase to another. ...

Electrochemical biosensors are normally based on enzymatic catalysis of a reaction that produces ions. The sensor substrate contains three electrodes, a reference electrode, an active electrode and a sink electrode. A counter electrode may also be present as an ion source. The target analyte is involved in the reaction that takes place on the active electrode surface, and the ions produced create a potential which is subtracted from that of the reference electrode to give a signal. Another example of an electrochemical biosensor, which is contrary to the current understanding of their ability, are screenprinted, conducting polymer coated, open circuit potential biosensors based on immunoassays. These biosensors only have two electrodes and are extremely sensitive, robust and accurate. They enable the detection of analytes at levels previously only achievable by HPLC and LC/MS and without rigourous sample preparation. The signal is produced by electrochemical and physical changes in the conducting polymer layer due to changes occurring at the surface of the senor such as; ionic strength, pH, hydration and redox due to the enzyme label turning over a substrate. An electrode is a conductor used to make contact with a nonmetallic part of a circuit (e. ... Reference electrode is an electrode which has a stable and well-known electrode potential. ... An electrode is a conductor used to make contact with a nonmetallic part of a circuit (e. ...

Thermometric and magnetic based biosensors are rare.

Applications

There are many potential application of biosensors of various types. The main requirements for a biosensor approach to be valuable in terms of research and commercial applications are the identification of a target molecule, availability of a suitable biological recognition element, and the potential for disposable portable detection systems to be preferred to sensitive laboratory-based techniques in some situations. Some examples are given below:

• Glucose monitoring in diabetes patients <-- historical market driver
• Other medical health related targets
• Environmental applications e.g. the detection of Pesticides and river water contaminants
• Remote sensing of airborne bacteria e.g. in counter-bioterrorist activities
• Detection of pathogens
• Determining levels of toxic substances before and after bioremediation
• Detection and determining of organophosphate

the plane is spreading pesticide. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Bioremediation can be defined as any process that uses microorganisms, fungi, green plants or their enzymes to return the environment altered by contaminants to its original condition. ... An organophosphate (sometimes abbreviated OP) is the general name for esters of phosphoric acid and is one of the organophosphorus compounds. ...

External links

• Biosensor research at Diepenbeek Belgium.
• Physiological Sensing Facility at Purdue University
• Paisly University

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 BY 

 J.JOHN BRITTO