PATTERNED NEURONAL ATTACHMENT AND OUTGROWTH ON SURFACE-MODIFIED, ELECTRICALLY CHARGED FLUOROPOLYMER SUBSTRATES

Fluorinated ethylenepropylene copolymer (FEP) and polyvinylidene fluor ide (PVDF) can generate static and transient electrical charges, respe ctively, after bulk molecular rearrangements induced by electrical cha rging techniques. Neurons cultured on electrically active FEP and PVDF show increased levels of nerve fiber outgrowth compared to electrical ly neutral material. The purpose of the present study was to determine if the addition of charged surface groups to the surfaces of FEP and PVDF would modify the influence of bulk electrical charges on cultured neurons. Mouse neuroblastoma (Nb2a) cells were cultured on electrical ly charged and uncharged FEP and PVDF substrates with covalently modif ied surfaces containing hydroxyl (OH) and amine (NH2) groups. Surface chemical modification was performed on the entire surface or in discre te striped regions. Nb2a cells cultured on electrically active FEP and PVDF showed greater levels of differentiation than cells on electrica lly neutral substrates. The presence of NH2 groups attenuated these re sponses in serum-containing media. Cells attached to NH2 rich surfaces generally displayed a flatter morphology and tended to remain attache d for longer time periods. Cells cultured on stripe-modified substrate s in serum-containing media showed a strong preferential attachment to modified regions, especially on NH2 stripes. In summary, bulk electri cal charges are more important than surface charges in stimulating Nb2 a cell differentiation. Surface groups serve to modulate neuronal morp hology and confer specific attachment promoting properties in serum-co ntaining media. The development of an optimal neuronal regeneration te mplate may require the incorporation of specific bulk and surface prop erties.