The adsorption of bovine serum albumin (BSA) at the TiO 2it is not the sole criterion. Compatibility also depends largely aqueous NaCl interface was studied as a function of pH and elecon what protein the surface denatures and in what sequence. trolyte concentration using kinetic and steady-state measure-For example, low-temperature isotropic carbon, which is a ments. The electrokinetic properties of BSA-covered TiO 2 particles good blood-compatible material, first adsorbs and denatures and the acid-base character of the protein were monitored by albumin in blood and passivates the substrate, preventing electrophoretic mobilities and acid-base potentiometric titration, the activation of blood coagulation proteins. Since during respectively. Some experiments were also outlined to analyze the implantation, proteins and macromolecules from the body different affinities of BSA monomers, dimers, and polymers for the surface. The adsorption process is fast; less than 10 min is fluids adsorb, and may promote or inhibit hemocompatibilenough to achieve steady-state conditions. All measured isotherms ity, a basic study of protein adsorption onto TiO 2 particles showed high initial slopes even under adverse electrostatic condicould contribute to elucidating the mechanisms involved in tions, resulting in high-affinity isotherms. Adsorption plateau valtitanium biocompatibility. Although titanium implantation ues ( G max ) had a great pH dependence; G max -pH curves reached has been reported in clinical studies lasting up to 25 years, a maximum at around the isoelectric point of BSA and showed a there are in the literature only a few works concerning prodrastic decrease on the acid side. Both structural and electrostatic tein adsorption on TiO 2 surfaces. In fact, most of the protein effects must be invoked to explain the diminution of adsorbed adsorption studies performed on inorganic surfaces involve BSA on either side of the isoelectric point. Structural effects were mainly to silica particles (7,(10)(11)(12)(13)(14)(15)(16)(17)(18), to a lower extent hemarelated to the different conformational states that BSA molecules tite (16, 19-21), and in a few, hydroxyapatite (22,23) or adopt with pH changes, whereas electrostatic effects were analyzed assuming that BSA molecules behave as soft particles. This reason-TiO 2 (2)(3)(4)18).
ing also allows us to explain the independence of the G max -pH A survey of the literature (20,(24)(25)(26) shows that several curves from electrolyte concentration.