Multiphase Intelligent Materials for Biomimetic Sensors

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Since the membrane-bound macromolecules provide the most general and Powerful mechanisms for biological ion-sensing and -channeling, a new type of polymer-modified electrode was designed : A multiphase material consisting of poly(styrene-co-acrylonitrile)and poly(Lglutamate)was synthesized as the block copolymer. The material has allowed us to immobilize synthetic polypeptides on a electrode just by dipping. A stable polymer membrane bearing the polypeptide as a chemoreceptive component was thus prepared on a Pt wire. Electrochemical responses toward 10^<-6> M of Ca^<2+> ion were obtained based on the permeability change of the redox active couple ions as the indicator. Such ion concentration-dependent changes in responses were seen also for Mg^<2+>, but not for Na^+, K^+, and tetrabutylammonium ions. On the other hand, electrochemical response towards urea was obtained by the same electrode. This seems to be the first example of an electrochemical sensor responsive to urea without depending upon the enzyme(urease). In addition, the modified electrode has a remarkable stability due to the vinyl polymer chains which serve as the building blocks of the membrane.The facile modification as well as the excellent stability should be ascribed to the multiphase structure ; vinyl-made membrane supporting 'synthetic ion channels'. Synthetic polypeptides have been studied extensively as models of proteins, though their use-in practical purposes has been rather limited. The present strategy would facilitate the use of synthetic polypeptides for advanced, intelligent materials.