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BIO(MIMETIC) ELECTROCHEMICAL SENSORS: PRESENT, PAST AND FUTURE Frieder W. Schellera, AysuYarmanb,Frank F. Bierc aUniversity of Potsdam, Institute of Biochemistry and Biology, Karl-LiebknechtStrasse 25-26, D-14476 Potsdam, Germany bTurkish-German University, Faculty of Science, Molecular Biotechnology, Sahinkaya Cad. No.:86, 34820 Beykoz, Istanbul, Turkey cFraunhofer Institute for Cell Therapy and Immunology, Branch Bioanalytics and Bioprocesses (IZI-BB), Am Mühlenberg 13, D-14476 Potsdam, Germany Biosensors represent the technical counter part of sense organs by coupling enzymes, antibodies, nucleic acids, receptors, organelles, cells, and tissues with a chemical or physical sensor. Inaugurated by L.C. Clarck in the sixties the development of electrochemical biosensors mainly focused on glucose oxidase and (PQQ) glucose dehydrogenase for blood glucose measurement. Ten years later direct heterogeneous electron transfer has been achieved by us for cytochrome c, hemoglobin and different P450 enzymes. This approach has been extended to develop sensors for the reactive oxygen species (ROS) superoxide and peroxide or for different xenobiotics and drugs. At present, electrochemical glucose sensors cover almost 75 percent of the17 billion US Dollars world marked of biosensors. On the other hand, electrochemical immunosensors or nucleic acid chips reached not a comparable acceptance and optical principles are considerably more applied in these fields. In order to mimic the active sites of antibodies or enzymes by synthetic mimics socalled „molecularly imprinted polymers”(MIPs) have been developed. Functional monomers are polymerised in the presence of the target analyte and after polymerisation the template molecules are removed, providing binding sites ideally complementary in size, shape and functionality to the template. So far the affinity and catalytic activity of MIPs have in general been lower than those of their biological counterparts. MIP–based electrochemical sensors have the potential to complement biosensor and biochips for the measurement of low molecular weight substances, proteins, viruses and living cells.