Patterned poly(chlorotrifluoroethylene) guides primary nerve cell adhesion and neurite outgrowth

Central nervous system (CNS) neurons, unlike those of the peripheral nervous system, do not spontaneously regenerate following injury. Recently it has been shown that in the developing CNS, a combination of cell-adhesive and cell-repulsive cues guide growing axons to their targets. We hypothesized that by mimicking these guidance signals, we could guide nerve cell adhesion and neurite outgrowth in vitro. Our objective was to direct primary nerve cell adhesion and neurite outgrowth on poly(chlorotrifluoroethylene) (PCTFE) surfaces by incorporating alternating patterns of cell-adhesive (peptide) and nonadhesive (polyethylene glycol; PEG) regions. PCTFE was surface-modified with lithium PEG-alkoxide, demonstrating the first report of metal-halogen exchange with an alkoxide and PCTFE. Titanium and then gold were sputtered onto PEG-modified films, using a shadow-masking technique that creates alternating patterns on the micrometer scale. PCTFE-Au regions then were modified with one of two cysteine-terminated laminin-derived peptides, C-GYIGSR or C-SIKVAV. Hippocampal neuron cell-surface interactions on homogeneously modified surfaces showed that neuron adhesion was decreased significantly on PEG-modified surfaces and was increased significantly on peptide-modified surfaces. Cell adhesion was greatest on CGYIGSR surfaces while neurite length was greatest on CSIKVAV surfaces and PLL/laminin positive controls, indicating the promise of peptides for enhanced cellular interactions. On patterned surfaces, hippocampal neurons adhered and extended neurites preferentially on peptide regions. By incorporating PEG and peptide molecules on the surface, we were able to simultaneously mimic cell-repulsive and cell-adhesive cues, respectively, and maintain the biopatterning of primary CNS neurons for over 1 week in culture.