Toxicity and biodistribution of nanodiamond coupled with calcein

Due to its small particle size, high specific surface area, functional capability and long-term stable fluorescence, nanodiamond (ND) has been widely used in biomedical applications including fluorescent probes, drug delivery and biological imaging. Nevertheless, the metabolism of ND and its derivatives is not yet well understood for diverse biomedical applications. In this study, to evaluate the cytotoxicity and biodistribution of the ND derivative, pure ND was functionalized with ethylenediamine (EDA) as a linker (ND-EDA) and then covalently labeled with an organic fluorescent dye called calcein. The modified ND is referred to as ND-EDA-calcein. Even at the maximum dose of 0.1 mg·mL −1 , the in vitro results for ND-EDA-calcein against HepG2 and LO2 cell lines showed negligible cytotoxicity, which was in line with the in vivo observations. In addition, it was found that following an intraperitoneal injection, ND-EDA-calcein could be accumulated mostly in the liver and kidney of the mice but not in the spleen. It is interesting to note that after 5 days following intraperitoneal injection, mice can totally metabolize the elimination of ND-EDA-calcein outside of their bodies. Therefore, our findings suggested that NDs can be considered for various nanomedicine applications including drug delivery and biomarkers.