1. Principle of biosensors

1.1 Definition

A biosensor consists of two essential components (figure 1 ): an immobilized sensitive biological element and a transducer. The immobilized biological element (e.g. antibody, enzyme, DNA, microorganisms) recognizes a target substance (e.g. antigen, substrate, complementary DNA) in a complex medium. The transducer translates the physico-chemical changes (e.g. photon emission, pH variation, mass) resulting from the recognition between the bioreceptor and the target molecule into a measurable electrical signal that correlates with the concentration of the target substance in the medium.

The choice of bioreceptor immobilization method and detection technique is...