Studies on the cytotoxicity of diamond nanoparticles against human cancer cells and lymphocytes

• A hydroxylated nanodiamond surface can be the first step for drug carriers.
• Nanodiamonds were cytotoxic after cell treatment in a serum-free medium.
• Serum proteins protected cultured cells from the toxic effects of nanodiamonds.
• Lymphocytes were less sensitive to the nanodiamond toxic activity than cancer cells.

Detonation nanodiamonds (DND) are a widely studied group of carbon nanomaterials. They have the ability to adsorb a variety of biomolecules and drugs onto their surfaces, and additionally their surfaces may be subjected to chemical functionalization by covalent bonds. We present a procedure for the purification and surface oxidation of diamond nanoparticles, which were then tested by spectroscopic analysis such as ATR-FTIR, Raman spectroscopy, and thermogravimetric analysis. We also examined the zeta potential of the tested material. Analysis of the cytotoxic effect of nanodiamonds against normal lymphocytes derived from human peripheral blood, the non-small cell lung cancer cell line (A549) and the human colorectal adenocarcinoma cell line (HT29) was performed using MTT colorimetric assay. Evaluation of cell viability was performed after 1-h and 24-h treatment with the tested nanoparticles applied at concentrations ranging from 1 μg/ml to 100 μg/ml. We found that the survival of the examined cells was strongly associated with the presence of serum proteins in the growth medium. The incubation of cells with nanodiamonds in the presence of serum did not exert a significant effect on cell survival, while the cell treatment in a serum-free medium resulted in a decrease in cell survival compared to the negative control. The role of purification and functionalization of nanodiamonds on their cytotoxicity was also demonstrated.