Nanodiamonds as intracellular transporters of chemotherapeutic drug

To explore the application of nanodiamonds (NDs) as anticancer drug delivery vehicles, firstly we examined the toxicity of NDs to three kinds of mammalian cells. The studies indicated that serum proteins in cell culture medium had significant effect. When cells were exposed to NDs dispersed in complete cell culture medium, no cytotoxicity was detected. However, severe cell death was found after exposed to NDs dispersed in serum-free medium. Possible reasons for serum-dependent cytotoxicity were discussed and the potential influence of serum on the test of efficacy was pointed for anticancer drug delivery system based on NDs. Then adsorption of anticancer drug 10-hydroxycamptothecin (HCPT) by NDs was studied. Experiments indicated that diluted NaOH solution could promote the loading of HCPT on NDs. And a slow release of HCPT from the HCPT-ND complex was established in low pH media. Assessments of cell viability and imaging with transmission electron microscopy demonstrated a much higher efficacy of the HCPT-ND complex compared with HCPT alone. On the basis of adsorption feature of ND aggregates, new strategy for the design of targeting drug delivery systems of NDs was proposed.