Received June 9, 2007

In Final Form: October 13, 2007

Abstract:

Cytochrome c (cyt c)-immobilized monolayers and multiple monolayers of a conducting polymer [poly(terthiophene-3-carboxylic acid) polymer (poly-TTCA)] were prepared, where the monolayer of monomer precursor was fabricated with the Langmuir-Blogett technique. Covalent immobilization of cyt c was achieved by the formation of an amide bond between the carboxylic groups of the conducting polymer and amines groups of lysine in cyt c. The monolayer of poly-TTCA and poly-TTCA/cyt c was characterized by cyclic voltammetry, XPS, EQCM, Auger electron spectra (AES), and atomic force microscopy (AFM). The immobilization of cyt c on the polymer layer reveals the direct electron-transfer processes of cyt c. Cyclic voltammetry of the poly-TTCA/cyt c-modified electrode showed a pair of reversible peaks at ~+212/+201 mV (E_pa/E_pc) versus Ag/AgCl in a 0.2 M phosphate buffer solution (pH 7.0). The peak separation and the redox peak current of the poly-TTCA/cyt c-modified electrodes were gradually increased by increasing the number of poly-TTCA/cyt c layers on the electrode. The heterogeneous electron-transfer rate constant (k_s) of cyt c at the poly-TTCA/cyt c-monolayer-modified electrode was estimated to be 0.874 s^-1. The method provides a novel route for the fabrication of protein (cyt c)-immobilized and/or lipid (palmitoyloleoylphosphatidic acid)-immobilized monolayers and multiple monolayers of a conducting polymer. Cyt c bonded on the conductive polymer layers was applied for bioelectronic devices with unique functionality.

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