Dynamic interfacial behaviour of bovine serum albumin solutions on titanium surfaces

In order to interpret the kinetics of the contact angles of biological model fluids in contact with titanium substrates, the time dependence of liquid/vapour and solid/liquid interfacial tensions is studied. The surface tension of the liquids is measured as a function of time by the pendant drop method and the surface tension of the solids is determined from the experimental contact angles of water and diiodomethane, using the geometric mean, the harmonic mean and the equation of state approaches. These values together with the contact angles measured before [A.P. Serro et al., Biomaterials, submitted] are used in the Young equation to obtain the solid/liquid interfacial tension. The liquid samples are Hank's balanced salt solution (HBSS) with a composition similar to the blood plasma and solutions of bovine serum albumin(BSA) in HBSS. The solid substrates are titanium samples of three types: oxidized by exposure to air (type 0), pre-incubated in HBSS (type 1) and pre-incubated in HBSS+BSA solutions (type 2). For all the substrates the solid/liquid interfacial tension involving the protein solution is higher than the equivalent value obtained with the solvent which should be related to the hydrophilicity of these substrates. The decrease of gamma(SL) with time for the substrate of type 2 may be explained by protein desorption. (C) 1997 Elsevier Science B.V.