Evaluation of glycine adsorption on diamond like carbon (DLC) and fluorinated DLC deposited by plasma-enhanced chemical vapour deposition (PECVD)

To gain a better understanding of protein adsorption onto biomaterial surfaces is required for the control of biocompatibility and bioactivity. Various samples of (DLC) and fluorine-doped DLC thin films (F-DLC) were deposited onto silicon substrates using plasma-enhanced chemical vapour deposition (PECVD) with source gases of Argon, acetylene (C2H2) and carbon tetra-fluoride (CF4). The adsorption of the simplest amino acid glycine on the surfaces of the thin films was investigated in order to elucidate the mechanism of protein adsorption on biomaterials. The properties of prepared films were examined using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, spectroscopic ellipsometry (SE) and atomic force microscopy (AFM). The results highlighted an increase in both the Id/Ig ratio and surface roughness with increasing the fluorine dopant levels. Following exposure to glycine solutions, the presence of bands at 1738 cm− 1, 1438 cm− 1 and 1199 cm− 1 indicates that the adsorption of glycine onto the surfaces has taken place via both deprotonated carboxyl and protonated amino groups. AFM analysis showed that the surface roughness value well significantly increased following exposure to glycine. The results indicate that at low fluorine doping the adsorption of the amino acid was enhanced whilst increased doping levels led to a reduced adsorption compared to undoped DLC. Therefore, doping of DLC may provide an approach to control the protein adsorption.

► Fluorine content DLC increases both the ID/IG value and surface roughness.
► Significant change of surface morphology after adsorption of glycine.
► Small amount of fluorine content DLC enhances the glycine adsorption.
► Glycine was bound to the surfaces via both carboxyl and amino groups.