Study of Human Serum Albumin Adsorption and Conformational Change on DLC and Silicon Doped DLC Using XPS and FTIR Spectroscopy

Abstract

Diamond-likecarbon (DLC) coatings are extremely useful for creating biocompatible surfaceson medical implants. DLC and silicon doped DLC synthesised on silicon wafersubstrate by using plasma enhanced chemical vapour deposition (PECVD). The effects of surface morphology on theinteraction of HSA with doped and undoped DLC films have been investigated. Thechemical composition of the surface before and after adsorption was analysedusing X-ray photoelectron spectroscopy(XPS) and Fourier transform infrared (FTIR). Results showed that siliconincorporation DLC tends to increase of sp3/sp2 hybridization ratio by decreasing sp2 hybridized carbon bondingconfigurations. Following exposure to solutions containing (0.250 μg/ml) HSA, theresults indicated that significant changes in the C, N and O levels on thesurfaces with reducing of the Si2p band at 100 eV. From FTIR spectrum, the peaks occur the following functional groups wereassigned as amide I and II groups at 1650 cm-1 and 1580 cm-1. Both XPS and FTIR spectroscopy confirm that HSA was bound onto the surfaces of the DLC and Si-DLCfilms via interaction of ionized carboxyl groups and the amino group did notplay a significant role in the adsorption of protein. These results from peakintensity show that an adsorbed layer of HSA is higher at high level (19%)silicon doping. Therefore doping of DLC may provide an approach to controllingthe protein adsorption.