ABSTRACT
Lifshitz-van der Waals (LW) and Lewis acid–base (AB), together with electrostatic (EL) forces are the non-covalent forces acting in adhesion in condensed phase media, such that the work of adhesion, W adh = W LW + W AB + W EL. In the case of serum albumin (SA) and glass surfaces or silica particles, on a macroscopic scale, W LW > 0, W AB < 0 and W EL < 0, so that W adh is negative, i.e. repulsive. Nonetheless, in aqueous media, at neutral pH, SA adheres to glass surfaces, as well as to silica particles. It may be hypothesized that on a microscopic level, negatively charged, electron-donating SA moieties, located on prominent sites with a small radius of curvature, can penetrate the macroscopic repulsion field and bind to electron-accepting cations imbedded in the glass surfaces (Ca ions) or in silica particles (Si ions). The correctness of the hypothesis is supported by the fact that all adhering SA can be desorbed from, say, silica particles with Na2-EDTA. Furthermore, energy vs. distance diagrams demonstrate that the more prominently located SA sites with a small radius of curvature should indeed be able to overcome the macroscopic repulsion field and to adhere locally to microscopic cationic sites in the glass or silica. Thus, energy vs. distance balances of the extended DLVO type (including AB as well as LW and EL forces), combining macroscopic and microscopic interactions, can be used to predict adhesion in complex systems.
