Low levels of maximal BSA adsorption onto bare silica. BSA adsorption isotherms onto bare SiO2 particles in two different media: 1 mM NaCl, pH 6.3 or 5 mM Tris.HCl, pH 7.4. Open and filled circles refer to two independent experiments with each mixture evaluated in duplicate. Interaction between silica particles and protein took place for 1 h at 25°C. Final silica concentration is 0.1 mg/ml. BSA adsorption was expressed either as adsorbed BSA concentration in mg/ml (A and C) or as number of BSA molecules adsorbed per m2 silica (B and D).