7. BIO-SENSOR
Biosensor is a device used for detection of any analyte, which combines a biological component with a physicochemical detector component. A biosensor is consists of,
(i) a sensitive biological element (eg. tissue, microorganisms, organelles, cell receptors, enzymes, antibodies, nucleic acids etc), which a biologically derived material or biomimic. These elements can be created by biological engineering.
(ii) the transducer, and
(iii) the detector element, that works in a physicochemical way; optical, piezoelectric electrochemical, thermometric, or magnetic.
Biosensor is in fact an integrated device consisting of a biological recognition element and a transducer capable of detecting the biological reaction and converting it into a signal, which can be processed. Ideally, the sensor should be self-contained, so that it is not necessary to add reagents to the sample matrix to obtain the desired response. There are a number of analytes (the target substances to be detected) which are measured in biological media: pH, partial pressure of carbon dioxide (pCO2), partial pressure of oxygen (pO2), and the ionic concentrations of sodium, potassium, calcium, and chloride. However, these sensors do not use biological recognition elements, and are considered chemical sensors. Normally, the biological recognition element is a protein or protein complex which is able to recognize a particular analyte in the presence of many other components in a complex biological matrix. This definition has since been expanded to include oligonucleotides. The recognition process involves a chemical or biological reaction, and the transducer must be capable of detecting not only the reaction but also its extent. An ideal sensor should yield a selective, rapid, and reliable response to the analyte, and the signal generated by the sensor should be proportional to the analyte concentration.
Why should we go for Biosensors:
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.
The biosensors are gaining importance in environmental monitoring as offer many advantages in comparison to many conventional analytical approaches in terms of simplicity, lower limits of detection and sensitivity. The potential for environmental applications lies in the ability of biosensors to measure the interaction of pollutants with biological systems through a biomolecular recognition capability. One of the greatest advantages that Biosensors frequently enjoy is their specificity due to their exploitation of biological molecules such as enzymes or antibodies. Also those allow rapid continuous control and are as specific as the immobilized system used in them. Involving the biological system, a biosensor runs little risks of environmental herm alike any chemical sensor. However, unlike any physicochemical technique, biosensors are susceptible to heat stress or any other factor capable of influencing the biological activities.
The Commercial Prospects
Biosensors are being used in three sectors like bioprocess industry, medical field and environmental detection of pollution and toxin. Maximum usage of biosensors is observed in medical science as glucose level detector or detector of enzymes. But in other sectors monitoring of a bioprocess is mostly limited to the measurement of pH, temperature, and dissolved oxygen. Its application to monitor the presence of product, either biomass, enzyme, or antibody, or of a by-product of the process as an indirect measure of process conditions, is getting pace day by day. Its environmental applications in detection of pesticide residues and river water contaminants especially the pathogens have been well emphasized and used widely.
The American Chemical Society has unearthed several analyte including a range of organophosphate and other pesticides, organic compounds like alcohol, ammonia, cyanide, phenol, RDX, BTEX, PCBs and heavy metals, biological parameters viz. BOD, DNA BIO-MARKERs etc. the process of commercialization of the biosensors are on and widening.
Description of A few commercially used Biosensors
1. Health care: This is the main area of application and practical application. Measurements of blood, gases, ions and metabolites are then necessary to show the patient's metabolic state. Many of these substrates have been determined by samples of urine and blood being taken away to a medical analytical laboratory for classical analysis, which may not he complete for hours or even days. The use of on the spot biosensors could enable analytical results to be obtained within minutes at most. The exactech glucose biosensors a reading in 30s.
2. Control of Industrial Processes: Biosensors can be used in various aspects of fermentation processes in three ways: i) offline in a laboratory ii) off-line, but close to the operation; and (iii) on - line, in real time. Such different types of monitoring could result in improved product quality, product yields, checks on tolerance of the variation in quality of raw materials, optimized energy efficiency. There are wide ranges of applications, in the food and drinks industry.
3. Environmental monitoring: There is an enormous range of potential analysis in air, water, soils and other situation. Such things as BOD, pesticides, fertilizers, industrial wastes and domestics' wastes require extensive analysis. Also veterinary science and mining are potential areas where biosensors could be used for environmental monitoring.
Biosensor application as cited by American Chemical Society
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Enzyme sensor (inhibition)
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Photosystem II (inhibition)
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Genetically engineered microorganisms (GEM) sensor
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Enzyme sensor (inhibition)
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Enzyme electrode, GEM sensor
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Formaldehyde (aqueous/vapor)
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Polychlorinated Biphenyls
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Immunosensor (continuous flow)
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Immunosensor (fiber optic, continuous flow)
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Chlorophyll fluorescence sensor
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Bacterial identification/enumeration
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Immunosensor, DNA sequence sensor
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Biological oxygen demand (BOD)
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GEM, bacterial, enzyme sensors
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BIO-MARKERs (DNA adducts)
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Bioremediation efficiency
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GEM, yeast, bacterial sensors
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