The Relationship Between Protein Adsorption-Desorption And Surface Micro-Nano Structure Of Hydroxyapatite Particle

Within milliseconds after biomaterials come in contact with a protein solution such as blood, interstitial fluid, culturemedium, proteins begin to adhere to the surface and form a protein film through a process known as protein adsorption. By the time cells arrive, the material surface has already been coated in a monolayer of proteins; hence, the host cells do not "see" the material but "see" instead a dynamic layer of proteins. Therefore, the protein adsorption behavior on biomaterial has become an index to evaluate its biocompatibility and biological activity.In this study, Hydroxyapatite (HAP) particles were hydrothermally synthesized with the surface morphologies adjusted by cyclohexane-1,2,3,4,5,6-hexacarboxylic acid (H6E) as a result of control of crystal nucleation, growth and growth orientation. HAP particles were characterized by XRD、 BET、 SEM、 FTIR and other equipments to determine the crystal structure, specific surface area, particle size distribution, surface morphology, surface functional groups and other aspects of characterization.Then, the experiments research the influence of adsorption systemtic factors(such as ultrasonic pre-process, protein concentration, PO43-concentration, pH) on zeta potential(ζ) and protein adsorption behaviors of HAP particles using bovine serum albumin(BSA), lysozyme(LYS) as model proteins.Subsequently, in order to understand the influence of surface morphology of HAP particle on protein adsorption process, we had studied the protein adsorption behaviors between BSA, Fibrinogen(FN), LYS and5kinds of HAP micro-nano particles which have different surface morphologies.Finally, the study researches the protein release tests of protein-loaded HAP carriers with different micro-nano surface morphologies in votro. It found out that micro-nano surface structure has a key role on release behaviors of protein-loaded HAP carriers. Hollow structure HAP particle shows an obvious protein drug delivery performance. Main conclusions are drawn as follows:(1) Five kinds of HAP micro-nano particles with different morphologies were fabricated by template-assisted hydrothermal procedures in different H6E concentrations of0 mM,0.5mM,1mM,5mM,50mM, which show ribbon, hedgehog-like, cauliflower like, pompon, shell-shaped, respectively.(2) ζ at different pH or PO43-concentration is always negative, of which ζ increases with pH increasing, increases initially and decreases gradually with PO43-increasing. Ultrasonic dispersing of HAP particles promotes protein adsorption. The BSA adsorption ability on HAP particles decreases as pH or PO43-concentration increasing. The LYS adsorption ability on HAP particles increases as pH increasing, decreases as increasing of PO43-concentration. The BSA or LYS adsorption ability on HAP particles increases as the increasing of protein concentration.(3) The micro-nano structure on HAP particles has a selective protein adsorption function for different proteins. The ribbon-like HAP is propitious to adsorption of acidic proteins (BSA and FN), on the contrary, the shell-shaped HAP has a strong affinity for alkaline protein (LYS).(4) The in vitro accumulative release quantity of protein increases as the increasing quantity of pre-adsorption of proteins. The protein-loaded shell-like HAP particle (HAP50-protein) shows an excellent protein release behavior in vitro. The release amounts and release rates of proteins through the protein loaded-HAP particles increase as the increasing of PO43-concentration.It was concluded that H6E can build micro-nano structures on the surface of HAP particles. The protein adsorption property on HAP particle relates to HAP dispersion, pH, PO43-concentration, protein concentration, HAP surface morphologies and many other factors. The micro-nano structure on HAP particles has a selective protein adsorption function for different proteins and a key role on release behaviors of protein-loaded HAP carriers. This work indicates that the design and synthesis of HAP crystals with well-controlled orientation through a simple approach is an effective method to improve their specificity for the adsorption-desorption of bio-related substances.