3D-nanoflowers of rutile TiO2 as a film grown on conducting and non-conducting glass substrates for in vitro biocompatibility studies with mouse MC3T3 osteoblast and human HS-5 cells

摘要

Thin films of 3D-nanoflowers of rutile TiO2 on conducting (FTO and ITO) and non-conducting (glass) substrates were grown using a surfactant free one-step hydrothermal process. Field emission scanning electron microscopy (FE-SEM) observations confirmed the transformation of TiO2 nanostructures from mesh-like to 3D-nanoflowers with an increase in hydrolysis rate during the growth of the TiO2 films. The X-ray diffraction (XRD) pattern of the TiO2 nanostructures as films grown on different substrates showed that under various conditions, they have a phase pure rutile crystallite structure. The high resolution transmission electron microscopy (HR-TEM) diffraction pattern of the TiO2 nanostructures showed tightly packed assemblies of titanium atoms and a lattice spacing of 0.23 nm along the longitudinal axis direction of rutile TiO2. X-ray photoelectron spectroscopic (XPS) analysis of the TiO2 nanostructures grown as films on glass substrates showed a spectral shift of 0.53 eV in binding energy, which confirms the charge accumulation on the non-conducting substrate, whereas there was no spectral shift observed for TiO2 films with similar structures grown on conducting substrates. The accumulated charge on the conducting surfaces can be easily neutralized, whereas the non-conducting surfaces may retain these accumulated charges. The adhesion, viability and proliferation response of mouse osteoblast (MC3T3) and human stromal (HS-5) cells on the 3D-nanoflowers of TiO2 as films grown on conducting and non-conducting substrates were assessed. The adhesion and proliferation of both the type of cells showed a better response on non-conducting surfaces as compared to conducting surfaces, despite the similar crystallite structures and nanomorphology of TiO2. Stromal cells had potential to prepare extracellular matrix scaffolds for the ex vivo expansion/differentiation of stem cells. Therefore, the current findings can be used to prepare 3D TiO2 nanostructure supported cellular scaffolds for regenerative medicine in the future.