Nanocrystalline diamond containing hydrogels and coatings for acceleration of osteogenesis

In the present study, we have compared the effects of ultrananocrystalline diamond/amorphous carbon composite films (UNCD/a-C) and nanocrystalline diamond (NCD) containing hydrogels to support the osteogenesis of endothelial progenitor cells (EPCs). The course of EPCs osteogenic differentiation was followed 21 days and assayed by measuring cell-associated alkaline phosphatase activity, calcium deposition, and expression of fibronectin. We found that EPCs were capable to adhere to both surfaces in flattened and elongated morphology. The attachment and spreading on the UNCD/a-C films were faster as compared to the hydrogels containing NCDs (by day 7), and this was connected with the release and adsorption of fibronectin to the surfaces. During the process of EPCs differentiation, the release of fibronectin was favored by hydrogels + NCD (day 21). The formation of calcium nodules, characteristic of osteoblastic mineralization, was detected by Alizarin Red S staining. Differentiation-induced calcium nodules were detected in EPCs growing on both surfaces. The EPCs cultured on hydrogels containing NCD deposited more extracellular calcium in comparison with those on UNCD/a-C films on day 21. These results were consistent with the data about the alkaline phosphatase activity on the same day and verified that an active EPC transformation to osteoblast phenotype occurred on both substrates. Our results could have direct implications in the use of biomaterials in tissue engineering strategies, and this work might be useful for the improvement of the methodologies for substrate preparation (including scaffolds). Thus both surfaces studied could be used for modification of bone implants (bone-anchoring parts of joint prostheses or bone replacements) in order to improve their integration with the surrounding bone tissue, for which improved cell–substrate adhesion is also needed.

Research Highlights
► Nanodiamond containing hydrogels and coatings for acceleration of osteogenesis.
► Support of osteogenic differentiation of endothelial progenitor cells.
► Nanodiamonds as biomaterials in tissue engineering strategies.