Antiaflatoxigenic effect of fullerene C nanoparticles at environmentally plausible concentrations.

Increased interest in fullerene C and derivatives in recent years implies an intensification of their environmental spread. Yet, the potential risks for living organisms are largely unknown, including the interaction of C with fungal organisms. This may be especially relevant for mycotoxigenic fungi since C may both scavenge and produce reactive oxygen species (ROS), and oxidative stress induces mycotoxin production in fungi. Therefore, this study examined effects of environmentally plausible concentrations of C (0, 10, 50, and 100 ng/mL) on Aspergillus flavus growth and aflatoxin production in culture media. In addition, ROS-dependent oxidative stress biomarkers-thiobarbituric acid reactive substances (TBARS), reduced and oxidised glutathione ratio, superoxide dismutase isoenzymes, catalase, glutathione peroxidase, and glutathione reductase were determined in mycelia. Nanoparticles of fullerene C (nC) did not exhibit strong antifungal activity against A. flavus. At the same time, nC caused an antiaflatoxigenic effect at 10-100 ng/mL, and 50 ng/mL unexpectedly enhanced aflatoxin production. The TBARS content, reduced and oxidised glutathione ratio, and copper, zinc superoxide dismutase activity suggest that 10 ng/mL nC exerted antioxidative action and reduced aflatoxin B1 production within fungal cells. Detected prooxidative effects of 50 ng/mL fullerene exceeded cellular defenses and consequently enhanced aflatoxin B1 production. Finally, the results obtained with 100 ng/mL nC point to prooxidative effects, but the absence of increase in aflatoxin output may indicate additional, presumably cytotoxic effects of nC. Thus, a range of rather low levels of nC in the environment has a potential to modify aflatoxin production in A. flavus. Due to possible implications, further studies should test these results in environmental conditions.