Influence of humic acid and UV-irradiation on iron-based nanoparticle toxicity in Girardia tigrine.

The rapid advancement of nanotechnology has led to the increasing application of metal oxide nanoparticles (NPs) in various fields, including agriculture, where they offer potential benefits such as improved nutrient delivery and pest control. However, concerns about their environmental impact necessitate a comprehensive assessment of their safety. This study investigated the potential toxic effects of iron-based nanoparticles (NPs) on freshwater planarian and the influence of abiotic factors such as humic acid (HA) and UV exposure on their toxicity. Three different types of iron-based NPs were tested, including commercially available Sigma iron oxide magnetic NPs (Sig_IOMNPs), biologically synthesized BS_IOMNPs and Zn-Fe and bulk FeSO4. Sigma and biogenic nanoparticles had predominantly magnetite (Fe3O4) structure whereas Zn-Fe possessed a bimetallic conformation. Interaction of these NPs with abiotic factors (HA and UV light) led to an increase in their hydrodynamic diameter. In contrast to the commercial sources (Sig_IOMNPs and bulk FeSO4), the biologically synthesized NPs did not cause any acute or sublethal toxicity to the planarian when alone or in combination with HA and UV. These results suggest that biologically synthesized iron-based NPs (Zn-Fe and BS_IOMNPs) may be a safe alternative to conventional bulk iron-based fertilizers. This study highlights the importance of investigating the physicochemical changes of NPs in environmentally realistic conditions and assessing their potential toxicity to aquatic organisms. These findings can contribute to the development of safe and sustainable agricultural practices, promoting the use of iron-based NPs as a new generation of fertilizers.