NEW DELHI, MARCH 16: Conventional techniques for detecting compounds of environmental, clinical and industrial importance are slowly giving way to biosensors which utilise biological components to detect such compounds.The development of biosensors to detect specific metals at low concentrations may help meet the demand for simple and sensitive analytical techniques to monitor metal levels. A number of biosensors relying on intact bacterial cells have recently been developed for monitoring toxic metals in the environment, says a report in the journal Tibtech.A biosensor combines a biological component (the sensing element), which is responsible for the selectivity of the device, with a detection system (the transducer) for measuring the reaction of the biological component with the substance (analyte) being monitored. The biological component can be an enzyme, antibody, receptor or even whole cells.The biological reaction can be detected by the activity of an enzyme, the binding of an analyte to anantibody or receptor, the induction of gene expression within cells or even cell death. Detection system for measuring these events usually rely on electrochemical or optical principles.Classical analytical methods of detection cannot distinguish between bio-available and unavailable pollutants because many toxic compounds accumulate in living organisms whose bio-availability determination is important.Simple biosensors have been developed for determining the biotoxicity of a sample. These cannot be used to determine the type of toxin present. When toxin-sensitive cells are exposed to critical amount of toxins, either the cells' metabolic activity decreases or the cells die.In any case, as the concentration of toxins in the cells' environment increases, there is a corresponding decrease in the signal produced by a reporter gene, a gene to monitor toxin levels.Non-specific biosensors have also been developed based on the heat-shock or stress-response displayed by many organisms. Organisms have a numberof general and specific mechanisms involving alterations in gene expression that they use to respond to unfavourable conditions, the report says.Only extensive testing of each individual biosensor system will determine its usefulness for measuring real samples.Microorganisms represent a wide genetic diversity that could be exploited in the development of biosensors that offer great sensitivity and selectivity.Despite the drawbacks, biosensors have considerable potential in applications for the detection and quantification of a wide variety of compounds that are otherwise difficult to monitor.
