Fabrication of conductive NGF-conjugated polypyrrole–poly(l-lactic acid) fibers and their effect on neurite outgrowth

In order to fabricate a tissue scaffold with the neurotrophic and electrical activities, conductive nerve growth factor (NGF)-conjugated polypyrrole–poly(l-lactic acid) (PPy–PLLA) composite fibers were prepared by oxidation polymerization and EDC chemistry with poly-l-lysine. PPy nanoparticles (∼70 nm diameter) accumulated on PLLA fiber surface to form a rough thick shell (∼200 nm thickness). These NGF-conjugated PPy–PLLA fibers could support PC12 neurite outgrowth and extension. Especially, 40% and 74% increase in PC12 neurite outgrowth and extension, respectively, could be obtained under electrical stimulation of 100 mV/cm voltages through the composite fibers. A mechanism for the interaction between neurite extension and the NGF-conjugated PPy–PLLA fibers under electro-stimulation was proposed, to explain the synergistic effect of the rough PPy shell, conjugated NGF and electricity on neurite outgrowth and elongation.