Formation mechanism of human serum albumin monolayers on positively charged polymer microparticles

• Published in: Colloids and surfaces, B, Biointerfaces B, Biointerfaces, 2017-11, Vol.159, p.929-936
• Main Authors: Nattich-Rak, Małgorzata, Sadowska, Marta, Adamczyk, Zbigniew, Cieśla, Michał, Kąkol, Małgorzata
• Format: Article
• Language: English
• Subjects: Adsorption of HSA on microparticles; HSA adsorption on microparticles; HSA monolayers; Maximum coverage of HSA on microparticles; Monolayers of HSA on microparticles; Zeta potential of HSA covered microparticles
• ISSN: 0927-7765; 1873-4367
• DOI: 10.1016/j.colsurfb.2017.08.051

[Display omitted] Mechanism of HSA adsorption on positively charge polymer microparticles •Maximum coverage of irreversibly adsorbed HSA positive and negative microparticles was determined.•A new bead model of the HSA molecule was developed.•Experimental data were quantitatively interpreted in terms of theoretical modelling.•Various orientations of HSA molecules on microparticles were predicted.•Electrostatic mechanism of HSA adsorption on microparticles was confirmed. Human serum albumin (HSA) adsorption on positively and negatively charged polystyrene microparticles was studied at various pHs and NaCl concentrations. Thorough electrophoretic mobility measurements were carried out that enabled to monitor in situ the progress of protein adsorption. The maximum coverage of irreversibly adsorbed HSA on microparticles was determined by different concentration depletion methods, one of them involving AFM imaging of residual molecules. An anomalous adsorption of HSA on the positive microparticles was observed at pH 3.5 where the maximum coverage attained 1.0mgm−2 for NaCl concentrations of 0.05M despite that the molecules were on average positively charged. For comparison, the maximum coverage of HSA on negatively charged microparticles was equal to 1.3mgm−2 at this pH and NaCl concentration. At pH 7.4 the maximum coverage on positive microparticles was equal to 2.1mgm−2 for 0.05M NaCl concentration. On the other hand, for negative microparticles, negligible adsorption of HSA was observed at pH 7.4 and 9.7. These experimental data were adequately interpreted in terms of the random sequential adsorption approach exploiting the bead model of the HSA molecule. Different orientations of adsorbed molecules, inert alia, the edge-on orientation prevailing for positively charged microparticles at pH 7.4, were confirmed. This was explained in terms of a heterogeneous charge distribution over the HSA molecule prevailing for a wide range of pHs.