Pre-treatment of titanium surfaces by fibronectin: in situ adsorption and effect of concentration

In this work, kinetics data on adsorption of fibronectin (Fn) on passivated Ti surfaces (Ti quartz crystals) in phosphate buffered saline (PBS) solution were obtained from in situ investigations with electrochemical quartz crystal microbalance (EQCM): from experiments performed at 15 and 60 mg l(-1) Fn solution concentrations, the maximum adsorption was reached within 30 min, and Fn adsorption seemed to be partially reversible, as about 15% of the initially adsorbed protein were removed upon PBS rinsing. The remaining amount of adsorbed Fn was around 1000 ng cm(-2) and was similar for both protein concentrations in solution. Moreover, differences in kinetics were observed between the two concentrations: the initial adsorption rate was much larger at 60 mg l(-1) than at 15 mg l(-1). Ex situ X-ray photoelectron spectroscopy (XPS) characterizations were used to examine the surface after adsorption under flow (EQCM measurements) or in static conditions: identification of the adsorbed protein and of the passivated TiO2 layer on metallic Ti. With bulk Ti samples, an isotherm of adsorption of Fn in PBS was established on the basis of a selection of Fn solution concentrations and on the maximum time required to get a steady state, for a given concentration. The equivalent thicknesses of adsorbed Fn (d(Fn) (XPS), model of a continuous layer adsorbed on the passivated Ti samples) were estimated by XPS. At saturation, a plateau is reached corresponding to an equivalent thickness of 5.5 nm for Fn solution concentrations larger than 50 mg l(-1). Thed(Fn) (XPS) values of the experiments performed under flow are in satisfactory agreement with the values determined from static adsorption experiments. Copyright (C) 2010 John Wiley & Sons, Ltd.