Modulating conformational stability of human serum albumin and implications for surface passivation applications

Human serum albumin (HSA) is one of the most abundant proteins in the human body and also used as a biomaterial coating. While there is significant interest in modifying the properties of solid supports to control HSA adsorption, there is an outstanding need to investigate whether modulating the conformational properties of HSA proteins can influence adsorption properties, especially in the context of surface passivation applications. Herein, we investigated how ionic strength - a key modulator of electrostatic forces influencing protein folding and protein-substrate interactions - can affect the conformational stability of HSA proteins and the resulting adsorption of HSA proteins onto silica surfaces for surface passivation applications. Thermal denaturation experiments identified that HSA is prone to unfolding and aggregation under physiologically relevant ionic strength conditions while HSA is more conformationally stable in low salt conditions. In line with these observations, we also determined that the adsorption of native HSA monomers onto silica surfaces was strongly influenced by electrostatic forces, with greater uptake in low ionic strength conditions. By contrast, the adsorption uptake of heat-denatured HSA was greatest in high ionic strength conditions and related to oligomer size. It was further revealed that native HSA is superior to heat-denatured HSA for passivating silica surfaces against serum biofouling. Taken together, our findings demonstrate that modulating the conformational stability of HSA proteins influences the adsorption pathway and passivation properties, offering fundamental insights that can lead to improved protein coatings.