Issue 21, 2013

Direct AFM force mapping of surface nanoscale organization and protein adsorption on an aluminum substrate

Abstract

We investigate the nanoscale organization of a superficially hydroxylated Al substrate and its effect on subsequent protein adsorption using atomic force microscopy (AFM). For this purpose we used a mode which allows a direct mapping of a variety of surface properties (adhesion, elasticity, dissipation, etc.) to be probed simultaneously with topographical images. The hydroxylation treatment leads to a drastic modification of the surface morphology, owing to the formation of AlOOH compounds. In air, AFM images revealed the formation of regular nanorod-like structures randomly distributed, inducing the appearance of nanoporous domains on the surface. In buffer solution, prior to the adsorption of proteins, the surface nanoscale organization is preserved, mainly due to the chemical stability of AlOOH compounds under these conditions. The adsorption of proteins on the obtained nanostructured surface was performed using either a globular (β-lactoglobulin) or a fibrillar (collagen) protein and by modulating the adsorbed amount through the incubation time or the concentration of proteins in solution. At low amounts, collagen adsorbs on the whole surface without preferential localization. The surface topography remains similar to the bare surface, while significant changes were evidenced on adhesion and elasticity maps. This is due to the fact that the surface became adhesive and less stiff, owing to the presence of a soft and hydrated protein layer. By contrast, β-lactoglobulin tends to diffuse into the nanoporous domains, leading to their filling up, and the surface is blurred with a thick and dense protein layer upon increasing the amount of adsorbed molecules. Our findings demonstrate the interest in using AFM for surface mapping to investigate the mechanism of protein adsorption at the nanoscale on materials with high surface roughness.

Graphical abstract: Direct AFM force mapping of surface nanoscale organization and protein adsorption on an aluminum substrate

Supplementary files

Article information

Article type
Paper
Submitted
11 Jan 2013
Accepted
03 Apr 2013
First published
05 Apr 2013

Phys. Chem. Chem. Phys., 2013,15, 8429-8440

Direct AFM force mapping of surface nanoscale organization and protein adsorption on an aluminum substrate

J. Landoulsi and V. Dupres, Phys. Chem. Chem. Phys., 2013, 15, 8429 DOI: 10.1039/C3CP00137G

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