Adsorption of Ferritin at Nanofaceted Al2O3 Surfaces

The influence of nanoscale surface topography on protein adsorption is of large importance for numerous applications in medicine and technology. Herein, the adsorption of ferritin at flat and nanofaceted Al2O3 surfaces is investigated by atomic force microscopy and X-ray photoelectron spectroscopy. The nanofaceted surfaces are generated by thermal annealing at temperature above 1000 °C, which leads to the formation of faceted saw-tooth-like surface topographies with perio-dicities of about 160 nm and amplitudes of about 15 nm. Ferritin adsorption at these nanofaceted surfaces is notably suppressed at a concentration of 10 mg/ml, which is attributed to lower ad-sorption affinities of the newly formed facets. Consequently, ferritin adsorption is restricted mostly to the grooves of the saw-tooth patterns, where the proteins can maximize their contact area with the surface. However, this effect depends on the applied protein concentration, with an inverse trend being observed at 30 mg/ml. Furthermore, different ferritin adsorption behavior is observed at topographically similar nanofacet patterns fabricated at different annealing temper-atures and attributed to different step and kink densities. These results demonstrate that while protein adsorption at solid surfaces can be notably affected by nanofacet patterns, fine-tuning protein adsorption in this way requires precise control of facet properties.