Surface modification of neural recording electrodes with conducting polymer/biomolecule blends

The interface between micromachined neural microelectrodes and neural tissu e plays an important role in chronic in vivo recording. Electrochemical pol ymerization was used to optimize the surface of the metal electrode sites. Electrically conductive polymers (polypyrrole) combined with biomolecules h aving cell adhesion functionality were deposited with great precision onto microelectrode sites of neural probes. The biomolecules used were a silk-li ke polymer having fibronectin fragments (SLPF) and nonapeptide CDPGYIGSR. T he existence of protein polymers and peptides in the coatings was confirmed by reflective microfocusing Fourier transform infrared spectroscopy (FTIR) . The morphology of the coating was rough and fuzzy, providing a high densi ty of bioactive sites for interaction with neural cells. this high interfac ial area also helped to lower the impedance of the electrode site and, cons equently, to improve the signal transport. Impedance spectroscopy showed a lowered magnitude and phase of impedance around the biologically relevant f requency of 1 kHz. Cyclic voltammetry demonstrated the intrinsic redox reac tion of the doped polypyrrole and the increased charge capacity of the coat ed electrodes. Rat glial cells and human neuroblastoma cells were seeded an d cultured on neural probes with coated and uncoated electrodes. Glial cell s appeared to attach better to polypyrrole/SLPF-coated electrodes than to u ncoated gold electrodes. Neuroblastoma cells grew preferentially on and aro und the polypyrrole/CDPGYIGSR-coated electrode sites while the polypyrrole/ CH3COO--coated sites on the same probe did not show a preferential attracti on to the cells. These results indicate that we can adjust the chemical com position, morphology, electronic transport, and bioactivity of polymer coat ings on electrode surfaces on a multichannel micromachined neural probe by controlling electrochemical deposition conditions. (C) 2001 John Wiley & So ns, Inc. J Biomed Mater Res 56: 261-272, 2001.