Biosensors or enzyme electrodes

Biosensors or enzyme electrodes INTRODUCTION OF BIOSENSORS:- Biosensors or enzyme electrodes invariably refer to such devices that sence and analyze biological informations. A biosensor is a device that detects, records, and transmits information regarding a physiological change or the presence of various chemical or biological materials in the environment. More technically, a biosensor is a probe that integrates a biological component, such as a whole bacterium or a biological product (e.g., an enzyme or antibody) with an electronic component to yield a measurable signal. Biosensors, which come in a large variety of sizes and shapes, are used to monitor changes in environmental conditions. They can detect and measure concentrations of specific bacteria or hazardous chemicals; they can measure acidity levels (pH). In short, biosensors can use bacteria and detect them, too. PRINCIPALS OF BIOSENSORS:- A biosensor essentially comprise of the following two major parts 1- Biological component- For sensing the presence as well as concentration of analyte. In the presence of a certain molecule the biological system changes the environment. The measuring device sensitive to this change sends a signal. This signal can be converted into the measurement parameter. Often the biological system is an actual cell. The key thing to remember is that it is an actual organism that detects the concentration change of the molecule in the media. This organism could be the same one as the one in the media or it could be different. In either case it must be kept separate from the media. This can be done with a membrane that is permeable to the molecule that is being measured but impermeable to the cells and most other macromolecules in the reactor media. 2- Physical component:- Transducer:- A device that converts energy from one form into another e.g., telephone companies use transducers to convert sound energy into electrical energy to be carried long- distance through telephone lines and then another transducer a t the receiving end to convert the electrical energy back into sound A biosensor is a sensing device that consists of a biological component coupled to a transducer that converts biochemical activity into, most commonly, electrical energy. Types of Biosensors:- There are different types of biosensors, which have different applications. These are listed below. Calorimetric biosensor Potentiometric biosensor Amperometric biosensors Optical biosensor Acoustic wave biosensors Calorimetric biosensor:- When the physical change is heat, released or absorbed by the reaction it is calorimetric biosensor. It measures the change in temperature in the solution containing analyte Separate thermistors measure the temperature of the solution before entry into the small packed bed column containing immobilized enzyme and also at the time of leaving the column. Calorimetric biosensors are most widely applicable and can be used to measure turbid and strongly coloured s olutions. Maintenance of constant sample temperature is the disadvantage of this type. At the transducer surface, an electrical potential is produced due to changed distribution of electrons and this type of biosensors are called potentiometric biosensors. They use ion sensitive electrodes, commonly pH meter glass electrodes for cations, glass pH electrodes coated with a gas-selective membrane for CO2, NH3 or H2S or solid-state electrodes. These electrodes convert the biological reaction into electric signal. Potentiometric Biosensors