Protein Adsorption on Biomaterial Surfaces: Subsequent Conformational and Biological Consequences – A Review

Abstract

Protein adsorption on solid surfaces is an immensely complex event comprising versatile biological and physico-chemical factors. This review focuses to ascertain the nature and biocompatibility of solid matrices essential for the medical needs during prosthetic implantations. It deals with number of important factors; nature of the biomaterial surfaces, the native protein structure, and induced configurational changes during the adsorbed state, andphysico-chemical influences liable for the event. The adsorption process demonstrates that solid surfaces are enabling to alter the protein structure. The conversion of neutral zymogens factor XII, and factor VII (FXII and FVII) to active enzymatic state (FXIIa and FVIIa) initiating the blood coagulation cascade following intrinsic or extrinsic pathway is a prime example regarding the configuration alteration during adsorbed state compared to its nativestate. Additionally, the activation of the complement cascade arises as a result of immune activation due to the adsorbed proteins on solid matrices. It is well known that interfacial tension compels the protein molecules to alter their structure, and is the prime factor behind the configuration transformation. Influences like contact angle, wettability, zeta potential and hydrophobicity along with other inter-aligned forces are involved. It is found that hydrophobic surfaces allow more proteins to bind but fail to activate the coagulation cascade. Contrarily, hydrophilic surfaces despite the feeble adsorption ability impose adequate changes to induce the enzymatic action. The nature of adsorption at the stationary state has been explained following the Gibbs' model of surface excess, Langmuir or any of the equivalent paradigms. But uniqueness in adsorption behavior is noticed in the ‘Vroman effect' while undergoing multiple protein interaction on the solid surfaces. Additionally, the property of cell adhesion heavily relies on the surface matter. Hydrophobicity, surface charge, chemical composition, and topography concertedly play crucial role. Further, prior adsorption of proteins on the adsorbent imposes profound effect on the cell and microbial adhesions which obviously depends on the character of proteins, and cells including the surface chemical composition of the adsorbents. The incident of bio-fouling which often enforces harmful effect arising from various implants is primarily instigated by the adsorption of proteins leading to subsequent invasion prompted by the immune cells. For avoidance, special categories of biomaterials are in the process of manufacturing. Despite having numerous adverse effects, cellular adhesion also shows few beneficial roles, like enhancing the growth of human vein endothelium cells and neurons. The adhesion of bacteria or microorganisms on many solid surfaces induces significantly different effects maintaining their longer survival period.