Evaluation of cellular influences induced by stable nanodiamond dispersion; the cellular influences of nanodiamond are small

The increased production of nanoparticles is providing increased investigation of the biological influences they induce. Studies of the biological influences of nanocarbons are also increasing. Some nanocarbons, such as carbon black, fullerene and carbon nanotubes, induce oxidative stress on cultured cells. On the other hand, there are few reports about the cellular influences of nanodiamond. A risk assessment based on accurate evaluation of biological influences is essential for the effective utilization of nanodiamond. In the present study, we prepared nanodiamond culture medium dispersions kept stable for the experimental period and examined their cellular influences. The secondary particle size of nanodiamond in the medium dispersion was 41–103nm. The dispersion was exposed to HaCaT and A549 cells at concentrations of 1.0, 0.1 and 0.01mg/mL for 6 and 24h. After that, mitochondrial activity, apoptosis, intracellular reactive oxygen level, lipid peroxidation, colony formation and cellular uptake were examined. Transmission electron microscopic observations showed cellular uptake of nanodiamond. Slight apoptosis and inhibition of colony formation were shown in the HaCaT cells at a concentration of 1.0mg/mL. Nanodiamond did not influence cell viability, cell membrane injury, or intracellular oxidative stress. Our results suggest that the cellular influences of nanodiamond are smaller than other nanocarbons. ► Nanodiamond-medium dispersion including nano-scale aggregates was prepared. ► Transmission electron microscopic observations showed cellular uptake of nanodiamond. ► The cellular influences were small when the zeta potential was negative. ► Positive zeta potential affects intracellular ROS level via protein adsorption.