Competitive protein adsorption mimicking in vivo behavior: Vroman effect on bioactive glasses

Abstract

Recent studies comparing the outcomes of in vitro and in vivo tests for bone-regenerating biomaterials revealed a very weak correlation between the two, highlighting the low reliability of the currently used in vitro models. Herein, it was proposed that this weak correlation is due to the poor knowledge concerning the intricate competitive adsorption of blood plasma proteins, namely the Vroman effect, on biomaterial surfaces post-implantation, which can form a protein layer that significantly impacts the implant’s properties. To address this, the singular and competitive adsorption profiles of the three main components of human blood plasma, human serum albumin (HSA), immunoglobulin G (IgG), and fibronectin (FN), were investigated on the surfaces of the FDA-approved and commercially available silicate bioactive glass (BG) S53P4. S53P4 surfaces were treated to increase the range of the investigated physicochemical properties, by conditioning the material with simulated body fluid (SBF) or subjecting it to 3-aminopropyltriethoxysilane (APTES) silanization, keeping the untreated material, as it is clinically used, as a control. Protein adsorption was implemented in static, semidynamic, and dynamic conditions, monitoring the process in real time with an electrokinetic analyzer. All the surfaces, before and after protein coating, have been finally imaged by confocal microscopy. Our findings indicate that SBF and APTES modifications significantly influence protein adsorption behavior. In the competitive adsorption of HSA, FN, and IgG onto bare and SBF-treated S53P4, HSA, likely due to its smaller size, has the lowest affinity, while FN and IgG appear to be more prevalent after displacing HSA. Nevertheless, HSA shows a strong affinity specifically to the S53P4 silanized with APTES, much higher than other protein-surface treatment combinations, potentially affecting in vivo biocompatibility of the APTES-treated BG. This study underscores the critical role of competitive protein adsorption and sheds light on the influence of surface treatments and assessment methods on the Vroman effect, advocating for more physiologically relevant in vitro models to improve the predictive accuracy for in vivo behavior.