Conducting polymers as a link between biomolecules and microelectronics

Biosensors based on electronic conducting polymers (ECPs) appear particularly well suited to the requirements of modern biological analysis: multiparametric assays, high information density and miniaturization. We describe a new methodology for the preparation of addressed DNA matrices. The process includes an electrochemically directed copolymerization of pyrrole and oligonucleotides bearing on their 5′ end a pyrrole moiety. The resulting polymer film deposited on the addressed electrode consists of pyrrole chains bearing covalently linked oligonucleotides. An oligonucleotide array was constructed on a silicon device bearing a matrix of 48 addressable 50 μm x 50 μm gold microelectrodes. This technology was successfully applied to the genotyping of Hepatitis C Virus in blood samples. Fluorescence detection results show good sensivity and a high degree of dimensional resolution. The need for versatile processes for the immobilization of biological species on surface led us to extend our methodology. A biotinylated surface was obtained by co-electropolymerization of pyrrole and biotin-pyrrole monomers. The efficiency for recognition (and consequently immobilization) of R-phycoerythrin-avidin was demonstrated by fluorescence detection. Copolymerization of decreasing ratios of pyrrole-biotin over pyrrole allowed us to obtain a decreasing scale of fluorescence.