We demonstrate herein a newly developed photoelectrochemical immunosensor for the determination of anti-cholera toxin antibody by using a photosensitive biotinylated polypyrrole film. The latter was generated by electro-oxidation of a biotinylated tris(bipyridyl) ruthenium(II) complex bearing pyrrole groups. The photoexcitation of this modified electrode potentiostated at 0.5 V vs SCE, in the presence of an oxidative quencher, pentaaminechloro cobalt(III) chloride (15 mM), led to a cathodic photocurrent. As a result of the affinity interactions, a layer of biotinylated cholera toxin was firmly bound to the functionalized polypyrrole film via avidin bridges. The resulting modified electrodes were tested as immunosensors for the detection of the corresponding antibody from 0 to 200 microg mL(-)(1). The antibody concentration was measured through the decrease in photocurrent intensity resulting from its specific binding onto the polymeric coating, the detection limit being 0.5 microg mL(-)(1).

This contribution reports, for the first time, the synthesis and electropolymerization of a pyrrole N-substituted by a nitrilotriacetic acid acting as a chelating center of Cu2+. A step-by-step approach for protein immobilization was developed via the successive coordination of Cu2+ and histidine-tagged proteins. The self-assembly of histidine-tagged glucose oxidase led to the formation of a close-packed enzyme monolayer at the poly(pyrrole) surface, and the reversibility and reproducibility of this affinity process were demonstrated.