Evaluation of Cytotoxicity and Bioimaging of Nitrogen-Vacancy Nanodiamonds

Nanodiamonds, due to their chemical inertness and biocompatibility, have found extensive uses in drug delivery and biomedical applications. Fluorescent nanodiamonds with fluorescent properties generated by nitrogen-vacancy defects have been intensively investigated for bioimaging, due to their high quantum yield and high photobleaching stability. In addition, the surface properties and particle size of nanodiamonds have significant impacts on cellular uptake and imaging quality. In this study, nitrogen-vacancy nanodiamonds with different particle sizes (40 nm and 90 nm) have been physicochemically characterised and investigated for their cytotoxicity and potential in fluorescence imaging. The nanodiamonds (with concentrations up to 100 µg/mL) showed cell viability >70% with mesenchymal stromal cells. The number of nanodiamonds was observed to have a larger impact on cell viability than the mass of nanodiamonds. Larger nanodiamonds (90 nm) exhibited a lower level of cytotoxicity, higher cellular uptake and fluorescence intensity. The results indicate the potential of using fluorescent nanodiamonds as a nanoprobe for effective bioimaging and cell tracking.