Application of a modified Coomassie brilliant blue protein assay in the study of protein adsorption on carbon thin films

The aim of this study is to investigate the adsorptive property of proteins on surfaces of three kinds of carbon films (DLC, CN0.088, and CN0.15) and the medical origin of PMMA. The carbon films were first synthesized by magnetron sputtering with different deposition parameters. The surface characteristics of both the carbon films and the original samples were then measured using a contact-angle meter. A modified Coomassie brilliant blue (CBB) protein assay (or Bradford method) was used to detect the amount of proteins adsorbed on the material surfaces after the pilot research for the optimal ratio of protein- to CBB-solution had been performed. The results of the pilot research show that the optimal ratio of protein- to CBB-solution is 1:3, and the protein adsorption results show that the sequence amounts of proteins adsorbed on four kinds of surfaces are DLC > CN0.088 > PMMA > CN0.15. This was the same as the hydrophobicity sequence of four kinds of surfaces obtained from the contact-angle test. However, the ratio of albumin to IgG (RA/I) adsorbed on the four surfaces has an order of PMMA > CN0.15 > DLC > CN0.088, which indicates the anti-thrombogenicity property of the four kinds of surfaces.