Electropolymerized Films in the Development of Biosensors

Abstract

The principles of chemical recognition have been widely used in analytical chemistry for the development of selective sensing devices. The recognition properties of several ionophores have been exploited to enable the design of advanced materials suitable for the preparation of fiber optic and potentiometric sensors. Specifically, sensors were prepared by electrochemically growing poly[Co(II)tetra(o-amino -phenyl)porphyrin] and poly[Co(II)tetra(p-hydroxyphenyl)porphyrin] on glassy carbon electrodes and indium(tin) oxide (ITΟ) slides. Further, a novel polymeric material was synthesized by the electrochemically mediated attachment of biotin to a surface. These films should allow for the formation of well-defined biotinylated interfaces, which can be utilized for numerous analytical purposes using the biotin-avidin interaction.Electrochemical polymerization (electropolymerization) has been recognized as a useful technique for the preparation of pinhole-free membranes (7,2) that have found numerous applications in electrocatalysis, amperometric biosensors, etc. These membranes are prepared by the electrodeposition of a polymeric film on the surface of an electrode that is immersed in a solution of an appropriate monomer. In order for polymerization to occur, groups that can be electrochemically oxidized or reduced to form a polymer need to be present in the monomer.This chapter reviews recent developments in our group regarding sensors based on electropolymerized porphyrins and biotin. An inherent advantage of these sensors, compared to conventional ones, is the retention of the active components (i.e., ionophore, metal-selective indicator, affinity ligand, etc.) in the polymer membrane. Indeed, leaching of the plasticizer or the ionophore from the polymer membrane to the aqueous sample solution reduces the lifetime of sensors (5-6). The existence of such leaching has been established previously by a variety of techniques (for a review of this subject see reference 7). This leaching usually worsens the detection limits of the sensors and results in a gradual deterioration of the response (5). Potentiometric and fiber optic sensors based on electropolymerized films present 1 Corresponding authors 0097-6156/94/0561-0295$08.00/0