Nanodiamond mediated delivery of chemotherapeutic drugs

Nanodiamond materials have been studied as potential drug carriers for cancer therapy. In this study, doxorubicin hydrochloride (DOX), a chemotherapy drug, was physically adsorbed onto red fluorescent nanodiamond (FND) with a size of similar to 140 nm. Our results revealed that FND carrying DOX (FND-DOX) can efficiently deliver the drug inside living HeLa cells via a clathrin-dependent endocytosis pathway. In contrast, the uptake of DOX occurs through an energy-independent passive diffusion mechanism. Both FND-DOX and DOX displayed similar uptake kinetics regardless of the uptake pathway. The results from the confocal fluorescence microscopy study showed that free DOX could enter the nucleolus, while the FND-DOX particles were distributed in the cytoplasm, but DOX detached from FND-DOX could migrate and enter the nucleolus. In vitro release of DOX from FND-DOX nanoparticles was found to be considerably slower than that of free DOX in phosphate-buffered saline (PBS, pH 7.4) at 37 degrees C. Further analysis of confocal fluorescence microscopy images and MTT assay also indicated that the FND-DOX system has a slow and sustained drug release capability. We propose that nanodiamond can potentially be effective as drug carriers for cancer therapy and so merits further study.