Effects of cobalt nanoparticles on human T cells in vitro.

Limited information is available on the potential risk of degradation products of metal-on-metal bearings in joint arthroplasty. The aim of this study was to investigate the cytotoxicity and genotoxicity of orthopedic-related cobalt nanoparticles on human T cells in vitro. T cells were collected using magnetic CD3 microbeads and exposed to different concentrations of cobalt nanoparticles and cobalt chloride. Cytotoxicity was evaluated by methyl thiazolyl tetrazolium and lactate dehydrogenase release assay. Cobalt nanoparticles dissolution in culture medium was determined by inductively coupled plasma-mass spectrometry. To study the probable mechanism of cobalt nanoparticles effects on T cells, superoxide dismutase, catalase, and glutathione peroxidase level was measured. Cobalt nanoparticles and cobalt ions could inhibit cell viability and enhance lactate dehydrogenase release in a concentration- and time-dependent manner (P < 0.05). The levels of cobalt ion released from cobalt nanoparticles in the culture medium were less than 40% and increased with cobalt nanoparticles concentration. Cobalt nanoparticles could induce primary DNA damage in a concentration-dependent manner, and the DNA damage caused by cobalt nanoparticles was heavier than that caused by cobalt ions. Cobalt nanoparticles exposure could significantly decrease superoxide dismutase, catalase, and glutathione peroxidase activities at subtoxic concentrations (6 μM, <CC(50)). These findings suggested that cobalt nanoparticles could generate potential risks to the T cells of patients suffer from metal-on-metal total hip arthroplasty, and the inhibition of antioxidant capacity may play important role in cobalt nanoparticles effects on T cells.