*Kahini Vaid *Siddharth Shukla
*Students of Biomedical Engineering (LDCE)
This report gives an overview about biosensors, their types, their construction, development and its future needs. A biosensor is an analytical device for the detection of an analyte that combines a biological component with a physicochemical detector component. I. INTRODUCTION
This report is a small presentation about biosensors and its types. A biosensor is an analytical device which converts a biological response into an electrical signal. Fig . The term 'biosensor' is often used to cover sensor devices used in order to determine the concentration of substances and other parameters of biological interest even where they do not utilize a biological system directly. Biosensors combine the exquisite selectivity of biology with the processing power of modern microelectronics and optoelectronics to offer powerful and new analytical tools with major applications in medicine, environmental studies, food and processing industries. It consists of 3 parts: the sensitive biological element biological material (e.g. 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 or the detector element (works in a physicochemical way; optical, piezoelectric, electrochemical, etc.) that transforms the signal resulting from the interaction of the analyte with the biological element into another signal (i.e., transducers) that can be more easily measured and quantified; associated electronics or signal processors that are primarily responsible for the display of the results in a user-friendly way. This sometimes accounts for the most expensive part of the sensor device; however it is possible to generate a user friendly display that includes transducer and sensitive element.
There are three so-called 'generations' of biosensors; First generation biosensors where the normal product of the reaction diffuses to the transducer and causes the electrical response, second generation biosensors which involve specific 'mediators' between the reaction and the transducer in order to generate improved response, and third generation biosensors where the reaction itself causes the response and no product or mediator diffusion is directly involved.  A successful biosensor must possess at least some of the following beneficial features: 1. The biocatalyst must be highly specific for the purpose of the analyses, be stable under normal storage conditions and, except in the case of colorimetric enzyme strips and dipsticks , show good stability over a large number of assays (i.e. much greater than 100). 2. The reaction should be as independent of such physical parameters as stirring, pH and temperature as is manageable. This would allow the analysis of samples with minimal pre-treatment. If the reaction involves cofactors or coenzymes these should, preferably, also be co-immobilized with the enzyme. 3. The response should be accurate, precise, reproducible and linear over the useful analytical range, without dilution or concentration. It should also be free from electrical noise. 4. The complete biosensor should be cheap, small, portable and capable of being used by semi-skilled operators. 5. There should be a market for the biosensor. There is clearly little purpose developing a biosensor if other factors (e.g. government subsidies, the continued employment of skilled analysts, or poor customer perception) encourage the use of traditional methods and discourage the decentralization of laboratory testing.  III. WORKING
A biosensor consists of the following two elements:
1. Bio element (Fig.)
2. Transducer Component
Fig 2 Bio-Element
The biological response of the biosensor is determined by the...