Cleaning of biomaterial surfaces: protein removal by different solvents.

The removal of biofilms or protein films from biomaterials is still a challenging task. In particular, for research investigations on real (applied) surfaces the reuse of samples is of high importance, because reuse allows the comparison of the same sample in different experiments. The aim of the present study was to evaluate the cleaning efficiency of different solvents (SDS, water, acetone, isopropanol, RIPA-buffer and Tween-20) on five different biomaterials (titanium, gold, PMMA (no acetone used), ceramic, and PTFE) with different wettability which were covered by layers of two different adsorbed proteins (BSA and lysozyme). The presence of a protein film after adsorption was confirmed by transmission electron microscopy (TEM). After treatment of the surfaces with the different solvents, the residual proteins on the surface were determined by BCA-assay (bicinchoninic acid assay). Data of the present study indicate that SDS is an effective solvent, but for several protein-substrate combinations it does not show the cleaning efficiency often mentioned in literature. RIPA-buffer and Tween-20 were more effective. They showed very low residual protein amounts after cleaning on all examined material surfaces and for both proteins, however, with small differences for the respective substrate-protein combinations. RIPA-buffer in combination with ultrasonication completely removed the protein layer as confirmed by TEM.