AbstractThe biological response to material surfaces is often influenced by protein layers formed at the bio-interface. Understanding this protein layer is of paramount importance for biomedical materials and cell culture devices, which often require protein coating for optimal cell growth. An insert system fitting exactly into standard tissue culture plates was developed and can be used for biological investigations without the influence of the cell culture material. Inserts prepared from polystyrene (PS), polycarbonate (PC), poly(styrene-co-acrylonitrile) (PSAN) and poly(ether imide) (PEI) exhibit a similar surface roughness and wettability so that only the chemistry is varied. Previously, stem cell adhesion responses were found to be different for these inserts, possibly because of their different protein adsorption profiles. This work investigated if the surface functional groups of these inserts influence their protein binding ability. Single and competitive adsorption of two most abundant blood proteins, human serum albumin (HSA) and immunoglobulin G (IgG) on these polymers was investigated by labeling both proteins with different near-infrared (IR) dyes. PEI showed the highest protein adsorption propensity in single and competitive adsorption of IgG and HSA while PS exhibited the least adsorption capability, whereas PSAN and PC showed an intermediate protein adsorption profile. Chemical inertness of PS could be the reason for this low protein binding ability and limited cell growth. Conclusively, a novel method to efficiently detect protein adsorption on polymer surfaces was established, and using this method the high relevance of the chemical composition of polymeric substrates on their protein adsorption profile could be proven.