Adsorption of fibrinogen on glass: reversibility aspects

The interactions of human fibrinogen with borosilicate glass have been studied using a radio-labeling technique. Adsorption in this system is not significantly affected by shear rate. Concentration dependence follows a Langmuir-like isotherm with plateau surface concentration of about 0.7 μg cm−2 in 0.05 M Tris, pH 7.35. With increasing NaCl or increasing Tris concentration, the level of adsorption decreases. Fibrinogen turnover between surface and solution is demonstrated by a double labeling technique. Only a fraction of the adsorbed layer is exchangeable under given conditions. The ratio of exchangeable to nonexchangeable fractions is found to increase with increasing concentrations of fibrinogen, NaCl, and Tris at pH 7.35. However this ratio is not significantly affected by shear. The rate of exchange is considerably faster than that observed previously (Brash and Samak, J. Colloid Interface Sci. 65, 495, 1978) for albumin on polyethylene. Although there is no desorption into the starting buffer, desorption (up to 80% of the adsorbed layer at the isotherm plateau) does take place into solutions of increased Tris concentration, even in the presence of fibrinogen. These data provide evidence of inherent reversibility in this system.