Mesoporous TiO₂ as a nanostructured substrate for cell culture and cell patterning

We investigated the behaviors of mammalian cells such as adhesion, morphology and proliferation on mesoporous TiO₂-coated glass slides using NIH-3T3 fibroblasts as a model cell. A sol-gel process using amphiphilic poly(vinyl chloride) (PVC)-g-poly(oxyethylene methacrylate) (POEM) graft copolymer as a template produced defect or crack-free and homogeneous mesoporous TiO₂ films over a large area with high porosity and good connectivity. Cells grown on the mesoporous TiO₂ surfaces exhibited less spreading and had more filopodia than cells on the flat glass slides. The nanotopographical cues from the mesoporous TiO₂ resulted in the formation of more focal adhesions, promoting cell adhesion and proliferation without decreasing cell viability and functionality. We also demonstrated the capability of controlling spatial placement of cells onto chemically and topologically structured templates by fabricating poly(ethylene glycol) (PEG) hydrogel micropatterns on mesoporous TiO₂ films. Because a hydrogel precursor solution could infiltrate and become crosslinked within the multilayered mesoporous TiO₂ films, the resultant hydrogel micropatterns were firmly anchored on the substrate without the use of adhesion-promoting monolayers. While nanoscale topographic cues from mesoporous structure contributed to enhancement of cellular behaviors, different chemistry between cell-repelling PEG hydrogel and cell-adhesive mesoporous region facilitated confinement of cells on the micrometer scale. This study suggests that developed mesoporous TiO₂ films hold high potential for bioapplications showing high biocompatibility as surface coating materials for implants or as biomimetic platforms for cell patterning.