ABSTRACT
Biosensors are normally composed of transducers and biological components (Figure 10.1), which are converted into physicochemical parameters such as ions, electrons, heat, mass, and light through speci€c reactions between biological components attached to the transducer surface and analytes that produce electric signals (Sethi, 1994). Biosensors are classi€ed according to the transduction mechanisms and biological components used. The four main categories based on the transduction mechanisms include piezoelectric, optoelectronic and electrochemical biosensors, and biothermisters. In addition, the biological components used in biosensors include enzymes, microbial, immuno-, and nucleic acids, biochips (protein, DNA, and cell chips), and biomimetic sensors, which utilize arti€cial biorecognition elements (electronic nose and electronic tongue). Due to the advancements in biomicroelectromechanical system technology, transducers used for biosensors have gradually been miniaturized, which has resulted in the development of micro–uidics technology. Moreover, in the case of some biosensors, the biological components are not immobilized onto the transducer surface, but rather are present in the vicinity of the transducer surface. Therefore, it is worth mentioning one de€nition of biosensors that was introduced by Cran€eld Biotechnology Center (UK): “A biosensor is a compact analytical device incorporating a biological or biologically derived sensing element either integrated within or intimately associated with a physicochemical transducer.”
