Controlling protein-particle adsorption by surface tailoring colloidal alumina particles with sulfonate groups

In this study, we demonstrate the control of protein adsorption by tailoring the sulfonate group density on the surface of colloidal alumina particles. The colloidal alumina (d(50) = 179 +/- 8 nm) is first accurately functionalized with sulfonate groups (SO3H) in densities ranging from 0 to 4.7 SO3H nm(-2). The zeta potential, hydrophilic/hydrophobic properties, particle size, morphology, surface area and elemental composition of the functionalized particles are assessed. The adsorption of three model proteins, bovine serum albumin (BSA), lysozyme (LSZ) and trypsin (TRY), is then investigated at pH 6.9 +/- 0.3 and an ionic strength of 3 mM. Solution depletion and zeta potential experiments show that BSA, LSZ and TRY adsorption is strongly affected by the SO3H surface density rather than by the net zeta potential of the particles. A direct correlation between the SO3H surface density, the intrinsic protein amino acid composition and protein adsorption is observed. Thus a continuous adjustment of the protein adsorption amount can be achieved between almost no coverage and a theoretical monolayer by varying the density of SO3H groups on the particle surface. These findings enable a deeper understanding of protein-particle interactions and, moreover, support the design and engineering of materials for specific biotechnology, environmental technology or nanomedicine applications. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.