Bovine serum albumin adsorption on titania surfaces and its relation to wettability aspects

The adsorption of bovine serum albumin (BSA) from sodium chloride solution and Hanks' balanced salt so- lution (HBSS) onto TiO2-silicon surfaces is studied by reflec- tometry in stagnation point flow. The results are compared with those obtained by dynamic contact-angle (DCA) analy- sis of titanium substrates. The adsorption isotherms show that the adsorbed amount of protein always is lower in HBSS, that is, in the presence of calcium and phosphate ions. This may be related to the increase in surface hydrophilicity caused by these ions, as suggested by the authors in previ- ous works. The rate of adsorption also is lower in HBSS solutions. Comparison of the initial adsorption rates with the rate of mass transfer to the surface reveals that in both solvents only a small fraction of the protein that arrives at the surface adsorbs onto it. Electrostatic and/or conforma- tional effects can explain the energy barrier to adsorption. The DCA analysis of high concentration (4 mg/mL) protein solutions shows a strong reduction of the contact-angle hys- teresis, both in HBSS and in NaCl solutions, which confirms that the immediate adsorption of the protein to the surface forms a stable, hydrophilic film. © 1999 John Wiley & Sons, Inc. J Biomed Mater Res, 46, 376-381, 1999.