Agarose hydrogels containing aminopropyl triethoxy silane (APTS) have been prepared and evaluated as scaffolds for adhesion and proliferation of human mesenchymal stem cells (hMSCs). The preparation of the hydrogels involved the conventional melting of agarose in water followed by addition of APTS as functional group carrier. The resulting hydrogel supports have been studied by Fourier transformed infrared spectroscopy in order to get an insight into the hybrid molecular structure. X-ray photoelectron spectroscopy has been used for the analysis of the surface chemical composition of the hydrogels. It is deduced from these data that the resulting hybrid structure presents two phases with a clear tendency toward APTS surface segregation. Moreover, the observation of the desiccated hydrogel surfaces by atomic force microscopy shows that the films acquire a filament-mesh structure for increasing APTS content, while the pure agarose supports exhibit a granular structure. As a result of such a structure, the hydrogel surfaces show a hydrophobic behavior, as determined by water contact angle measurements. The biocompatibility of such platforms is supported by adhesion-proliferation assays performed with hMSCs. It is concluded that although adhesion is lower on APTS rich scaffolds, the proliferation rate on these surfaces is higher so that total number of proliferating cells does not significantly depend on APTS content in the hydrogels.

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.

Ti-doped ZnO thin films were obtained with the aim of tailoring ZnO film bioadhesiveness and making the optoelectronic properties of ZnO materials transferable to biological environments. The films were prepared on silicon substrates by sol–gel spin-coating and subsequent annealing. A Ti–O segregation limits the ZnO crystallite growth and creates a buffer out-layer. Consequently, the Ti-doped ZnO presents slightly increased resistivity, which remains in the order of 10 –3 Ω·cm. The strong biochemical interference of Zn 2+ ions released from pure ZnO surfaces was evidenced by culturing Staphylococcus epidermidis with and without the Zn 2+ coupling agent clioquinol. The Ti-doped ZnO surfaces showed a considerable increase of bacterial viability with respect to pure ZnO. Cell adhesion was assayed with human mesenchymal stem cells (hMSCs). Although hMSCs find difficulties to adhere to the pure ZnO surface, they progressively expand on the surface of ZnO when the Ti doping is increased. A preliminary microdevice has been built on the Si substrate with a ZnO film doped with 5% Ti. A one-dimensional micropattern with a zigzag structure shows the preference of hMSCs for adhesion on Ti-doped ZnO with respect to Si. The induced contrast of surface tension further induces a cell polarization effect on hMSCs. It is suggested that the presence of Ti–O covalent bonding on the doped surfaces provides a much more stable ground for bioadhesion. Such fouling behavior suggests an influence of Ti doping on film bioadhesiveness and sets the starting point for the selection of optimal materials for implantable optoelectronic devices.

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