Cysteine-induced hormesis effect of silver nanoparticles.

The toxicity of silver nanoparticles (AgNPs) is widely exploited, but their hormesis effect has, so far, received little attention. This study reports the hormesis effect at low AgNPs concentrations of 0.34 mg L-1, with a 29.9% increase in bacterial viability compared with the control. Cysteine can induce a hormesis effect at a higher concentration. 12.5 mg L-1 cysteine induced a hormesis effect in the AgNP concentration range of 1.7-5.1 mg L-1. Results suggest that this cysteine-induced hormesis effect is concentration-dependent; the concentration that make sulfuration rate (ns/nAg) of 6.15 shows strong excitation to cells.