DYNAMIC INTERFACIAL BEHAVIOR 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. Th e 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 deter mined 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 be fore [A.P. Serro et al., Biomaterials, submitted] are used in the Youn g equation to obtain the solid/liquid interfacial tension. The liquid samples are Hank's balanced salt solution (HBSS) with a composition si milar to the blood plasma and solutions of bovine serum albumin(BSA) i n HBSS. The solid substrates are titanium samples of three types: oxid ized by exposure to air (type 0), pre-incubated in HBSS (type 1) and p re-incubated in HBSS+BSA solutions (type 2). For all the substrates th e solid/liquid interfacial tension involving the protein solution is h igher 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 p rotein desorption. (C) 1997 Elsevier Science B.V.