The preparation of polypyrrole surfaces in the presence of mesoporous silica nanoparticles and their biomedical applications.

The deposition of carboxylic acid-terminated conducting polymer into two- or three-dimensional structures made up of colloidal particles has been successfully completed. This was accomplished using electrochemical deposition of ordered arrays of mesoporous silica nanoparticles (MSNs) as a template. Subsequent removal of the template yielded a porous polypyrrole surface. The co-polymerization of pyrrole with carboxylic acid-terminated pyrrole derivatives overcame the limitations of a lack of reactive functional groups--by facilitating the direct coupling of the film with biomolecules or drugs on the surface. Such Ppy films were characterized by several techniques: (1) scanning electron microscope (SEM) to evaluate surface topography, (2) x-ray photoelectron spectroscopy (XPS) to assess the chemical composition of the films, (3) four-point probe to measure the conductivity, and cyclic voltammogram to observe surface electroactivity. To assay the biological effectiveness of this preparation, we used phase-contrast light microscopy to compare neurite outgrowth from PC 12 cells grown on Ppy films in the presence and absence of electrical stimulation. These electrically functional, biocompatible composites show promise as novel neural implants that would deliver specific biologically active molecules in a highly localized manner to damaged or otherwise vulnerable cells such as found in the nervous system.