Polypyrrole doped with 2 peptide sequences from laminin.

In the field of neural tissue engineering, electrically conducting, biocompatible surfaces are of great interest. Over the past several decades conducting polymers have been studied as candidate surfaces because they fit these criteria. Several attempts have been made to combine the conductivity and biocompatibility of conducting polymers with biomolecules that could promote specific cell attachment and growth. In this report the laminin fragments CDPGYIGSR (p31) and RNIAEIIKDI (p20) are used as dopants in electropolymerization of the conducting polymer polypyrrole (PPy). The electrical properties of the resulting films are analyzed by impedance spectroscopy and cyclic voltammetry and compared to gold. PPy/p20 surfaces consistently demonstrate the lowest impedance and largest charge capacity for a given deposition charge. Next, in vitro studies using primary neurons cultured in a defined media and primary astrocytes in a serum containing media were performed; neuron density and neurite length, as well as astrocyte density, were quantified. Surfaces doped with a combination of the two peptides (PPy/p20-p31) consistently supported the highest neuronal density. It is shown that surfaces doped with the laminin fragment p20 had significantly longer primary neurites than either the p31 doped or poly(styrenesulfonate) doped PPy surfaces. Finally, the astrocyte studies demonstrate that PPy surfaces have significantly less astrocyte adhesion in culture than the common electrode material, gold.