KINETICS OF DNA-BINDING TO ELECTRICALLY CONDUCTING POLYPYRROLE FILMS

We investigated the kinetics of P-32 end labeled DNA binding from solution to electrochemically prepared polypyrrole (PPy) thick films. These data were found to fit a simple diffusion-limited binding model with low phenomenological activation energy (5 kcal/mol), consistent with diffusion-limited binding kinetics. These data suggest that the DNA binds to PPy without significant alteration of its structure. The binding of double-helical PNA to PPy was found to be dependent upon the presence of the electrooxidized positively, charged surface functional groups on PPy. DNA adsorption kinetics are only moderately affected by changes in ionic strength and pH in the 5-9 range. A twofold increase in binding rate is observed for single-stranded DNA compared to the double-stranded DNA binding level. DNA desorption and competitor-driven desorption studies were performed to characterize the binding state and release of DNA from the polypyrrole,substrates. These data suggested that a significant fraction of the DNA was reversibly bound, consistent with the low measured activation energy.