Polymeric membranes and coupled enzymes in the design of biosensors

Abstract

Biosensors are new analytical tools associating a biologically active sensing membrane with a specific transducer which can be electrochemical, thermal, optical or based on mass variation. Sensing corresponds to the selective molecular recognition, generally by enzymes or antibodies, of a target analyte followed by the occurrence of a physico-chemical signal converted by the transducer into an electrical signal. This signal can be correlated to the concentration of the target analyte. Two main roles can be attributed to the membrane; it enables the immobilization or confinement of the bioactive material capable of molecular recognition in the immediate vicinity of the transducer tip and ensures additional selectivity to the system. The role of the membranes is described for enzyme electrodes which are the first operational biosensors now in use. Some useful immobilization procedures and design of anti-interference multilayer membranes are detailed. Extension of the role of membranes to optical system is exemplified with fiber-optic biosensors based on fluorescence or luminescence. Finally a coating procedure with ultrathin layers of microsensors is presented showing promise for the development of bioelectronics in the near future.