Effects of structural and chemical properties of surface coatings on the adsorption characteristics of proteins

Using Quartz Crystal Microbalance with Dissipation (QCM-D) and Atomic Force Microscopy (AFM), a series of functional surface coatings were investigated to establish the effects of surface structural and chemical properties on the adsorption characteristics of two model proteins, β-Lactoglobulin (β-Lg) and Bovine Serum Albumin (BSA). We show that a free contact scenario, e.g., droplet, that is widely used to evaluate surface energy, is not always equivalent to biofouling conditions where the liquid phase is continuous - releasing the entrapped air from surface geometries could influence the interfacial adsorption process of biomolecules. We observed that surface structuration favoured adsorption of both proteins, especially for the protein of smaller size (β-Lg) as larger amounts of molecules would be required to fill surface geometries. Compact proteinaceous adlayers were observed on the coatings without structure, particularly those containing -CF3 ligands, suggesting stronger adhesion mechanisms due to conformational reorientations of both proteins to facilitate surface binding, especially BSA. In contrast, surface structure led to the formation of soft adlayers as the filling of surface cavities might affect protein conformation and favour protein superposition, hindering removal. We demonstrate how protein-surface binding affinity and packaging density of adsorbed proteins can be modulated as a synergistic effect of surface chemistry and structure, which is of especially importance to the development of anti-fouling coatings.