Albumin adsorption at solid substrates: A quest for a unified approach.

Adsorption of human serum albumin (HSA), recombinant HSA (rHSA) and the albumin dimer (dHSA) at solid/electrolyte interfaces is reviewed with the emphasis put on quantitative analysis of this process. Initially, various physicochemical data characterizing bulk properties of albumin molecules are discussed such as electrophoretic mobility, electrokinetic charge, zeta potential and diffusion coefficient. Adsorption kinetics of HSA, rHSA and dHSA at mica derived from AFM, streaming potential and XPS measurements is analyzed. Maximum coverages of irreversibly adsorbed molecules under various ionic strengths and pHs are quantitatively interpreted in terms of the random sequential adsorption model. Thorough acid-basic characteristic of albumin monolayers of well-controlled coverage are also presented. The results derived from the colloid deposition method that unveil albumin molecule orientation and charge distribution are discussed and interpreted in terms of the random site theory. Subsequently, adsorption of albumins at negatively and positively charged polymeric microparticles studied by the electrokinetic and the AFM aided concentration depletion methods is analyzed. These results are theoretically interpreted by applying the bead model of HSA and dHSA molecules. Orientation of adsorbed molecules and the stability of albumin monolayers in respect to pH cyclic changes are discussed. A universal, electrostatic interaction driven, mechanism of albumin adsorption at macroscopic surfaces and polymer microparticles is confirmed.