Optical and structural phase transitions in TiO₂ nanoparticles with osteogenic differentiation potential

Herein, titanium dioxide nanoparticles were synthesized employing a simple sol-gel method followed by calcination at four different temperatures (450 °C, 650 °C, 850 °C, and 1050 °C). Effect of calcination temperature on surface morphology, particle shape and size, phase transitions, optical properties, and osteogenic differentiation were then studied. Phase changes (anatase, anatase-rutile, and rutile) of TiO₂ nanoparticle were observed as the calcination temperature increased to 450 °C, 650 °C, 850 °C, and 1050 °C. The surface morphology also transformed from smooth to granular as the calcination temperature increased from 450 °C to 1050 °C. The particle size of titanium dioxide nanoparticles was found to be about ∼ 300 nm. It remained almost the same as the calcination temperature increased from 450 °C to 850 °C. Optical spectra of TiO₂ nanoparticles prepared at 450, 650, and 850 °C showed maximum absorbance in the visible-NIR region whereas TiO₂ nanoparticles prepared at 1050 °C displayed maximum absorbance in the UV region with a distorted morphology. TiO₂ nanoparticles prepared at 450 °C and 650 °C were found to have excellent biocompatibility as suggested by cell viability analysis using fibroblasts. In addition, hBM-MSCs were used to evaluate osteogenic differentiation of different structural phases of TiO₂ nanoparticles calcined at various temperatures.