In vitro response of human osteoblasts to multi-step sol-gel derived bioactive glass nanoparticles for bone tissue engineering

A multi-step sal-gel process was employed to synthesize bioactive glass (BC) nanoparticles. Transmission electron microscopy (TEM) revealed that the BC nanoparticles were spherical and ranged from 30 to 60 nm in diameter. In vitro reactivity of the BC nanoparticles was tested in phosphate buffer saline (PBS), Tris-buffer (TRIS), simulated body fluid (SBF), and Dulbecco's modified Eagle's medium (DMEM), in comparison with similar sized hydroxyapatite (HA) and silicon substituted HA (SiHA) nanoparticles. Bioactivity of the BC nanoparticles was confirmed through Fourier transform infrared spectroscopy (FTIR) analysis. It was found that bone-like apatite was formed after immersion in SBF at 7 days. Solutions containing BC nanoparticles were slightly more alkaline than HA and SiHA, suggesting that a more rapid apatite formation on BC was related to solution-mediated dissolution. Primary human osteoblast (HOB) cell model was used to evaluate biological responses to BC nanoparticles. Lactate dehydrogenase (LDH) cytotoxicity assay showed that HOB cells were not adversely affected by the BC nanoparticles throughout the 7 day test period. Interestingly, MTS assay results showed an enhancement in cell proliferation in the presence of BC when compared to HA and SiHA nanoparticles. Particularly, statistically significant (p < 0.05) alkaline phosphatase (ALP) activity of HOB cells was found on the culture containing BC nanopartides, suggesting that the cell differentiation might be promoted by BC. Real-time quantitative PCR analysis (qPCR) further confirmed this finding, as a significantly higher level of RUNX2 gene expression was recorded on the cells cultured in the presence of BC nanoparticles when compared to those with HA and SiHA.