Impact of Fe3O4-porphyrin hybrid nanoparticles on wheat: Physiological and metabolic advance

Iron-magnetic nanoparticles (Fe-NMPs) are widely used in environmental remediation, while porphyrin-based hybrid materials anchored to silica-coated Fe₃O₄-nanoparticles (Fe₃O₄-NPs) have been used for water disinfection purposes. To assess their safety on plants, especially concerning potential environmental release, it was investigated for the first time, the impact on plants of a silica-coated Fe₃O₄-NPs bearing a porphyrinic formulation (FORM) - FORM@NMP. Additionally, FORM alone and the magnetic nanoparticles without FORM anchored (NH₂@NMP) were used for comparison. Wheat (Triticum aestivum L.) was chosen as a model species and was subjected to three environmentally relevant doses during germination and tiller development through root application. Morphological, physiological, and metabolic parameters were assessed. Despite a modest biomass decrease and alterations in membrane properties, no major impairments in germination or seedling development were observed. During tiller phase, both Fe₃O₄-NPs increased leaf length, and photosynthesis exhibited varied impacts: both Fe₃O₄-NPs and FORM alone increased pigments; only Fe₃O₄-NPs promoted gas exchange; all treatments improved the photochemical phase. Regarding oxidative stress, lipid peroxidation decreased in FORM and FORM@NMP, yet with increased O₂^-• in FORM@NMP; total flavonoids decreased in NH₂@NMP and antioxidant enzymes declined across all materials. Phenolic profiling revealed a generalized trend towards a decrease in flavones. In conclusion, these nanoparticles can modulate wheat physiology/metabolism without apparently inducing phytotoxicity at low doses and during short-time exposure. ENVIRONMENTAL IMPLICATION: Iron-magnetic nanoparticles are widely used in environmental remediation and fertilization, besides of new applications continuously being developed, making them emerging contaminants. Soil is a major sink for these nanoparticles and their fate and potential environmental risks in ecosystems must be addressed to achieve more sustainable environmental applications. Furthermore, as the reuse of treated wastewater for agricultural irrigation is being claimed, it is of major importance to disclose the impact on crops of the nanoparticles used for wastewater decontamination, such as those proposed in this work.