Effect of Immobilized Nerve Growth Factor on Conductive Polymers: Electrical Properties and Cellular Response This work was supported in part by the National Institutes of Health (NINDS-N01-NS-1-2338), the National Science Foundation (DMR-0084304, DMR-0518079), the NASA BioScience and Engineering Institute, the Undergraduate Research Opportunity Program, the training program in Regenerative Sciences, and the University of Michigan, College of Engineering.

Abstract

The use of biologically active dopants in conductive polymers allows the polymer to be tailored for specific applications. The incorporation of nerve growth factor (NGF) as a co-dopant in the electrochemical deposition of conductive polymers is evaluated for its ability to elicit specific biological interactions with neurons. The electrochemical properties of the NGF-modified conducting polymers are studied by impedance spectroscopy and cyclic voltammetry. Impedance measurements at the neurobiologically important frequency of 1 kHz reveal that the minimum impedance of the NGF-modified polypyrrole (PPy) film, 15 kω, is lower than the minimum impedance of peptide-modified PPy film (360 kω). Similar results are found with NGF-modified poly(3,4-ethylene dioxythiophene) (PEDOT). The microstructure of the conductive polymer films is characterized by optical microscopy and electron microscopy and indicates that the NGF-functionalized polymer surface topology is similar to that of the unmodified polymer film. Optical and fluorescence microscopy reveal that PC-12 (rat pheochromacytoma) cells adhered to the NGF-modified substrate and extended neurites on both PPy and PEDOT, indicating that the NGF in the polymer film is biologically active. Taken together these data indicate that the incorporation of NGF can modify the biological interactions of the electrode without compromising the conductive properties or the morphology of the polymeric film.