The dynamics, kinetics and reversibility of protein adsorption onto the surface of biodegradable materials

Dynamic contact angle (DCA) analysis was used to investigate the kinetics and dynamics of protein interactions in a time-dependent manner for a group of organic natural-based surfaces during their initial contact with aqueous and protein solutions. Starch-based biomaterials were used to analyze the influence different materials with different surfaces had on the adsorption, desorption and configuration of proteins. Polymeric blends of starch and cellulose acetate (SCA), polycaprolactone (SPCL) and ethylene vinyl alcohol (SEVA-C) were used. The model protein systems included single protein solutions of human serum albumin, fibronectin, vitronectin and fibrinogen, and also complex solutions of human blood plasma. In the adsorption studies, very small and nearly equal advancing and receding contact angles were measured for all the materials. Highly wetting and low contact angle hysteresis, therefore, are exhibited by these surfaces. This effect was more noticeable for SCA surfaces. Moreover, the effect of protein concentration was also assessed and demonstrated to substantially affect the DCA wetting forces of SEVA-C and SPCL surfaces. In the desorption studies, during the rinsing phase with saline solution, the DCA loops became larger than that observed for the adsorption phase, which indicated increases in the contact angle hysteresis. The hysteresis of SCA and SPCL surfaces reversibly changed through the desorption phase, at the end of which, hysteresis was comparable to that of surfaces immersed in saline solution. The results indicated that adsorbed proteins could desorb more readily on SCA and SPCL than on SEVA-C. In the later case, stronger interactions such as hydrophobic forces were established and it is likely the rearrangement of protein conformation had occurred. Monitored by DCA, the evolution of hysteresis demonstrated the progressive bond strengthening between protein molecules and solid substratum, further elucidating the behaviour of proteins that regulate cellular interactions with implanted devices.The authors acknowledge funding from the Foundation for Science and Technology (FCT), Portugal for SFRH/BD/11188/2002 and for partial funding through FEDER and POCTI programmes and EU funded Project HIPPOCRATES (NMP3-CT-2003-505758). This work was carried out under the scope of the European Network of Excellence EXPERTISSUES (NMP3-CT-2004-500283)