MAGNITUDE AND POLARITY OF A FLUOROETHYLENE PROPYLENE ELECTRET SUBSTRATE CHARGE INFLUENCES NEURITE OUTGROWTH IN-VITRO

Positively charged coating materials such as polylysine improve neuron al attachment in vitro. Due to the structural complexity of these char ged molecules, it is unclear whether neuronal effects are due to charg e or to physicochemical effects, or both. Polymeric materials with cha rge storage capabilities and defined surface properties may provide a model in which electrical charge and surface property effects can be s eparated. Fluorinated ethylenepropylene (FEP) films can store negative or positive charges injected through a corona charging process, thus generating a negative or positive external electrostatic field. In the present study, mouse neuroblastoma (Nb2a) cells were cultured on posi tive, negative, and uncharged FEP substrates, in both serum-containing and serum-free media. Cell attachment, differentiation, and neurite o utgrowth were assessed 24, 48, 72 and 96 h after plating. Electron spe ctroscopy for chemical analysis (ESCA), contact angle analysis, and sc anning electron microscopy (SEM) revealed no differences in surface ch emistry and topography between positive, negative, and uncharged FEP. No significant differences in the levels of cell attachment on positiv e negative, and uncharged substrates were observed. Significantly high er levels of neurite outgrowth, however, were observed with positive s ubstrates as compared to negative and uncharged substrates, in both me dia conditions. Substrates charged to +1000 V showed greater levels of outgrowth compared to +500 and +3000 V, suggesting the presence of an optimal range of charge for neurite outgrowth. These results show tha t cell/charge interactions mediate cell effects on electrically charge d substrates with identical surface chemistry, topography and adhesivi ty. (C) 1993 John Wiley & Sons, Inc.