Preparation of orpiment nanoparticles and their cytotoxic effect on cultured leukemia K562 cells

An investigation has been made into the antitumor effect on K562 cells of orpiment nanoparticles which were prepared chemically and analyzed by transmission electron microscope and energy dispersive spectrometry (EDS). Methyl thiazolyl tetrazolium and flow cytometry assays were performed to examine their antitumor effect compared with that of traditional orpiment at various concentrations. The average diameters of the two types of orpiment nanoparticles prepared were 60 nm and 140 nm, respectively, and EDS identified that only orpiment was present. Orpiment nanoparticles greatly inhibited the proliferation of K562 cells by apoptosis, in a concentration-and time-dependent manner, much more effectively than traditional orpiment (p < 0.001). The survival ratio of cells treated with orpiment nanoparticles at 2, 4, 8, and 16 micromol/l after 72 h was 23.0%, 10.1%, 3.2%, and 0.5%, respectively, much lower than 80.0%, 69.0%, 52.3%, and 31.7% of cells treated with traditional orpiment at the corresponding concentration for 72 h. The IC50 of orpiment nanoparticles in K562 cells for 48 h was only 1.27 micromol/l, in comparison with 13.0 micromol/l of traditional orpiment. After treated with orpiment nanoparticles at 4, 8, and 16 micromol/l for 48 h, the apoptotic rate of cells was 11.55%, 20.70%, and 26.45%, respectively, but that in cells treated with traditional orpiment at the same concentration for 48 h was only 3.16%, 3.86%, and 6.46%, respectively. Thus, orpiment nanoparticles can produce a much better cytotoxic effect on cancer cells than that of traditional orpiment.