IMPROVED CELL-ADHESION TO ION BEAM-IRRADIATED POLYMER SURFACES

A very strong improvement of the cell adhesion, spreading and prolifer ation was observed for ion beam irradiated surfaces of polyethersulpho nes and polyurethane. The improvement shows a characteristic ion fluen ce-dependence with a threshold around 1 x 10(15) ions cm(-2). We have compared this improvement of surface cytocompatibility with the variou s ion-induced chemical and physical modifications of the polymeric sur faces, taking into account their characteristic fluence-dependence. Th e irradiation induced a severe compositional and chemical modification of the polymeric surfaces as detected by X-ray photoelectron spectros copy. Contact angle measurements showed that the surface free energy w as strongly modified by ion irradiation. The fluence-dependent formati on of a hydrogenated amorphous carbon phase was demonstrated by Raman spectroscopy. Our findings indicate that neither the simple modificati on of the functional groups nor the mere elemental composition nor the modification of the surface free energy can explain the observed flue nce-dependence of the cell adhesion enhancement. On the contrary, we s how that this enhancement correlates with the formation of a highly sp ecific ion-induced 'unsaturated' a-C:H phase. According to these findi ngs, we suggest that the formation of a substantial amount of hydrogen ated amorphous carbon phases is the major factor promoting the cytocom patibility of ion irradiated polymer surfaces. (C) 1997 Elsevier Scien ce Limited. All rights reserved.