Long-term craniofacial osteoblast culture on a sodium phosphate and a calcium/sodium phosphate glass

The aim of this study was to determine the characteristics of human craniofacial osteoblasts cultured on sodium phosphate glass and calcium-sodium phosphate glass in a long-term culture of up to 28 days. The characteristics studied were attachment, proliferation, alkaline phosphatase activity, collagen-1 production, and mineralization. A comparison of the degradation rate, measured by mass loss of the glasses, which are intended for use as a component of a novel degradable composite for craniofacial bone repair, was also performed. It was our hypothesis that the glass would be degradable with a change in degradation rate observed by calcium addition and support osteoblast proliferation and expression of the above characteristics. The inclusion of calcium into the reaction mixture significantly decreased the degradation rate, and it is suggested that the slower degradation is the result of pseudo crosslinking (ionic crosslinks rather than covalent bonding) of the polyphosphate chains by the calcium ions. Therefore, twice as many P-O bonds will need to be hydrolyzed for dissolution of the metal phosphate to occur, therefore greatly reducing the rate of hydrolysis. Osteoblasts were able to attach, spread, and proliferate in a manner comparable with the positive control, as shown by analysis of variance. Formation of a collagen-rich mineralized matrix was also observed. The results presented here suggest that a biocompatible soluble glass has been produced, which has potential to be included in a novel biodegradable craniofacial implant.