Electrically controlled release of the nerve growth factor from a collagen-carbon nanotube composite for supporting neuronal growth.

We report the use of a nerve growth factor-loaded collagen-carbon nanotube (NGF-Col-CNT) composite as a substrate for in vitro growth of PC 12 cells. The feasibility of such novel composites as drug carriers was assessed using an in vitro drug-release test (ELISA immunoassay) in the presence of an electrical field. Subsequent studies included four-point probes, cyclic voltammograms, and in vitro PC 12 growth of fibers. The facile incorporation of NGF within fibrous collagen structures significantly mediated PC 12 (nerve) fiber process formation during the application of electrical voltage. Indeed, electrical stimulation (500 mV) using non-polarized Ag/AgCl electrodes to electro-active composites facilitated the sustained release of NGF. Given that PC 12 cells require NGF in the media to produce fiber outgrowth, this assay was clearly informative when the differentiation and branching of PC 12 cells into neurons was significantly enhanced. NGF responses were also evident from other developmental events including protrusions of neuronal filopodia and the formation of microspikes. Col-CNT composites, when electrically stimulated, could serve not only as neuronal scaffolds, but also as an electrically controllable drug release system to improve the performance and preferential timing of growth factor release in various biomedical applications.