ABSTRACT
A biosensor should respond selectively, continuously, rapidly, specifically, and ideally without added reagent, and then different criteria must also be considered. The abundant literature that can be related to the keyword Biosensor proves without doubt that the field is attractive. It is an interdisciplinary area for which sharp limits cannot be defined easily. The concept of biosensor has evolved; for some authors it is a self-contained analytical device that responds selectively and reversibly to the concentration or activity of chemical species in biological samples. A first chemical or physical signal consecutive to molecular recognition by the bioactive layer is converted by the transducer into a second signal, generally electrical, with a transduction mode that can be electrochemical, thermal, optical, or based on mass variation. The biosensing element must be either intimately connected to or integrated within a physicochemical transducer. Numerous attempts to find a universal transducer that matches any kind of reaction have been reported.
