Potential impact of engineered silver nanoparticles in the control of aflatoxins, ochratoxin A and the main aflatoxigenic and ochratoxigenic species affecting foods

The potential use of nanotechnology in the control of toxigenic fungi and mycotoxin production has been little explored. In this report, engineered silver nanoparticles (AgNPs) were synthesized and characterized by single particle Inductively Coupled Plasma Mass Spectrometry. Then, their effectiveness in the control of the growth of the main aflatoxigenic and ochratoxigenic species affecting foods and aflatoxins (AFs) and ochratoxin A (OTA) production was studied. The target species and their associated mycotoxins were Aspergillus flavus (AFB(1) and AFB(2)), A. parasiticus (AFB(1), AFB(2), AFG(1) and AFG(2)), A. carbonarius, A. niger, A. ochraceus, A. steynii, A. westerdijkiae and Penicillium verrucosum (OTA). Spore suspensions supplemented with AgNPs (average diameter size 30 rim, range 14-100 nm) at doses 0-45 mu g/mL were incubated for 2-30 h. At selected exposure times aliquots were removed and cultured on maize-based medium (MBM) for 10 days. In these cultures, percentage of viable spores, effective doses (EDs) to inhibit the number of viable spores to 50%, 90% and 100%, colony lag phases, colony growth rates (GR), EDs to inhibit the colony GR to 50%, 90% and 100% were estimated. AF and OTA levels were determined by UPLC-MS/MS. Under the assayed conditions, effective doses of the AgNPs against all the studied fungal species could be estimated. These doses generally decreased with increasing exposure time and were higher for A. flavus and A. parasiticus than for ochratoxigenic species. Colonies from spores treated at high exposure times (20-30 h) and variable AgNP doses showed long lag phases or even did not occur depending on the fungal species. Colony GR, as well as AF and OTA levels in MBM cultures decreased when AgNP dose and contact period increased. The factors species, AgNP dose, exposure time and their interactions significantly affect fungal growth and AF and OTA accumulation in MBM. The results suggest that AgNPs only or as active ingredient hosted in paints, films or other polymers could be a good strategy in the management of the main aflatoxigenic and ocratoxigenic species affecting food and AF and OTA contamination.