The surface properties of porous silicon (PSi) evolve rapidly in phosphate-buffered saline. X-ray photoelectron spectra indicate the formation of a Si-OH and C-O enriched surface, which becomes increasingly hydrophilic with aging time. Multiscale stripe micropatterns of Si and PSi have been fabricated by means of a high-energy ion-beam irradiation process. These micropatterns have been aged in physiological conditions and used to analyze human mesenchymal stem cell (hMSC) adhesion. The actin cytoskeleton of hMSCs orients following the uniaxial micropatterns. In the wider Si stripes, hMSCs are dominantly located on Si areas. However, for reduced Si widths, adhesion is avoided on PSi by a split assembly of the actin cytoskeleton on two parallel Si areas. These results confirm that nanostructured Si-OH/C-O-rich surfaces with hydrophilic character are specially adapted for the creation of cell adhesion surface contrasts.

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The biomedical applications of ZnO are drastically limited by its intrinsic solubility, which shortens the stability and lifetime of devices. We show that the functionality of ZnO in human mesenchymal stem cell (hMSC) studies is limited due to poor cell adhesion. The sol-gel route has been employed to obtain zinc titanate thin films for their integration as surface protective layer on ZnO. These films were obtained from zinc acetate (ZnAc) and titanium isopropoxide (TIPT). So derived xerogels were dried and their thermal evolution studied by TGM-DTA to identify critical annealing temperatures. The evolution of the microstructure and composition of spun cast films was determined by XRD and FTIR. Organic and ionic byproducts were eliminated at T>300°C, which kickstarts a transformation of the amorphous materials into polycrystalline. Thin films consisted of the ZnTiO3 perovskite from annealing temperatures of 500°C. Cell adhesion on the synthesized samples (both amorphous and crystalline) was assayed by culturing hMSCs. Immunofluorescence images of actin cytoskeleton were obtained and proliferation studied using Ki67. Cell density, single cell area and proliferation rates on ZnTiO3 films were closer to control TiO2 surfaces than to ZnO films. Such behavior validates the short term biocompatibility of ZnTiO3 films and its potential use as surface layer for ZnO biomedical devices.

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