Visualisation of human plasma fibrinogen adsorbed on titanium implant surfaces with different roughness

Direct visualisation of adsorbed human plasma proteins on biomaterial surfaces may help the understanding of the performance of implants. The aim of this study was the visualisation of human plasma fibrinogen (HPF) adsorbed on different titanium implants with characterised surface properties. Seven types of titanium samples were used: mechanically polished (P); mechanically ground (G); sand blasted with alumina (B); sand blasted with alumina and etched in HF/HNO3 (BN); sand blasted with alumina and etched in HCl/H2SO4 (SLA); mechanically polished and etched in HCl/H2SO4 (PSLA); and plasma sprayed (TPS). The surface morphology and roughness of these surfaces were analysed by atomic force microscopy (AFM). The surface chemical composition of the implants was analysed by X-ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectrometry (ToF-SIMS). The seven processing methods influenced the roughness and produced distinct morphologies of the implant surfaces. The main chemical constituent of all surfaces was TiO2, with some samples showing the presence of other elements. HPF adsorbed on the titanium surfaces was visualised by AFM phase imaging. Visualisation of the adsorbed HPF was successfully achieved on samples P and G, but not on the other five samples. Differences in the dimensions and in the phase contrast of HPF molecules adsorbed on P and G surfaces were observed and discussed. No correlation between surface topography and morphology of the adsorbed proteins was observed on surfaces P and G. Possible reasons for not detecting HPF with AFM on five of the seven sample types were attributed to the surface physico-chemical properties of these samples.