Enzyme or protein immobilization techniques for applications in biosensor design

New generations of biosensors are emerging that are based on novel and promising transducers such as miniature, reagentless-mediated electrodes, field-effect transistors, piezoelectric and optical devices. Reagentless-mediated biosensors can be constructed by co-immobilizing both enzymes and mediators onto a miniaturized electrode using electropolymerization, thus improving the sensitivity and speed of the response. Even more promising is the development of electrochemical sensors, in which electron transfer is made directly from a redox enzyme to an electrode surface via molecular wires. While this has only been reported, so far, for a specific enzyme entrapped in N-methylpyrrole under defined circumstances, the development of new oriented immobilization techniques, coupled with progress in protein engineering, may make direct electron transfer the rule rather than the exception.