Enhanced Proliferation and Growth of Non-Differentiated and Osteoblast-Differentiated Human Stem Cells on the Surface of HVOF-Sprayed Nano TiO2-HA Coatings

HVOF-sprayed biomedical coatings produced from nano-TiO₂ and nano-TiO₂+10wt%HA powders have been engineered as possible future alternatives to APS HA coatings. This approach was chosen due to (i) the stability of TiO₂ in the human body (i.e., no dissolution) and (ii) bond strength values on Ti-6Al-4V substrates more than two times higher than those of APS HA coatings. To explore the bioperformance of these novel materials, human mesenchymal stem cells (hMSCs) and osteoblast differentiated-hMSCs (hMSCs-ob) were cultured from 1 to 21 days on the surface of HVOF-sprayed nano TiO₂ and nano TiO₂+10wt%HA coatings. APS HA coatings and Ti-6Al-4V substrates were employed as controls. The active profiles of the hMSCs and hMSCs-ob were evaluated via (i) biochemical analysis (alkaline phosphatase activity (ALP), osteocalcin (OC), type I C-terminal collagen propeptide (CICP)), (ii) cytoskeleton organization (confocal microscopy) and (iii) cell/substrate interaction (SEM). The biochemical analysis indicted that the bioactivity of the hMSCs and hMSCs-ob on the surface of HA and nano TiO₂+10wt%HA coatings exhibited similar levels. However, the cytoskeleton organization and the cell/substrate interaction evaluation demonstrated a higher degree of cell proliferation and attachment on the surface of the HVOF-sprayed nano TiO₂+10wt%HA coatings. These results are considered promising for the development of biomedical coatings.