Nanodiamonds of Different Surface Chemistry Influence the Toxicity and Differentiation of Rat Bone Mesenchymal Stem Cells .

The nanodiamonds (NDs) have attracted much attention in biomedical applications due to their excellent magnetic and optical properties. However, comprehensive study of different surfacemodified NDs on toxicity and differentiation of mesenchymal stem cells are very deficient. In this study, three types of NDs, i.e., ND-COOH, ND-NH₃ and ND-PEG were co-cultured with rat bone mesenchymal stem cells (MSCs) to assess their biosafety and effects on differentiation. In a dry state, they had a similar diameter of about 6-7 nm, and aggregated into ˜100 nm (hydrodynamic size) in cell culture medium. Co-culture with MSCs showed that the ND-COOH and ND-PEG had lower cytotoxicity than ND-NH₃. Alkaline comet assay showed slight genotoxicity for all the NDs regardless of their surface coatings. The reactive oxygen species (ROS) test showed that the cytotoxicity and genotoxicity of NDs may be attributed to the NDs-mediated intracellular oxidative stress. All the NDs did not show significant impact on the osteogenic differentiation of MSCs, whereas the ND-COOH and ND-PEG slightly impaired the adipogenic differentiation. Taken together, these findings provide some momentous implications for the design of surface chemical structures of NDs for their applications in biological field.