Toxicity assessment of cobalt ferrite nanoparticles on wheat plants

Cobalt ferrite nanoparticles (NPs) have received increasing attention due to their widespread therapeutic and agricultural applicability. In the environmental field, dry powder- and ferrofluid-suspended cobalt ferrite NPs were found to be useful for removing heavy metals and metalloids from water, while diluted suspensions of cobalt ferrite NP have been promisingly applied in medicine. However, the potential toxicological implications of widespread exposure are still unknown. Since cobalt ferrite NPs are considered residual wastes of environmental or medical applications, plants may serve as a point-of-entry for engineered nanomaterials as a result of consumption of these plants. Thus, the aim of this study was to assess the effects of dry powder and fresh cobalt ferrite NP on wheat plants. Seven-day assays were conducted, using quartz sand as the plant growth substrate. The toxicity end points measured were seed germination, root and shoot lengths, total cobalt (Co) and iron (Fe) accumulation, photosynthetic pigment production, protein (PRT) production, and activities of catalase (CAT), ascorbate peroxidase (APX), and guaiacol peroxidase (GPX). Increasing total Co and Fe in plant tissues indicated that wheat plants were exposed to cobalt ferrite NP. Seed germination and shoot length were not sufficiently sensitive toxicity end points. The effective concentration (EC₅₀) that diminished root length of plants by 50% was 1963 mg/kg for fresh ferrite NPs and 5023 mg/kg for powder ferrite NP. Hence, fresh ferrite NPs were more toxic than powder NP. Plant stress was indicated by a significant decrease in photosynthetic pigments. CAT, APX, and GPX antioxidant enzymatic activity suggested the generation of reactive oxygen species and oxidative damage induced by cobalt ferrite NP. More studies are thus necessary to determine whether the benefits of using these NPs outweigh the risks.

钴铁氧体纳米颗粒（nanoparticles, NPs）因其广泛的治疗与农业应用潜力而受到越来越多的关注。在环境领域中，干粉及铁磁流体悬浮的钴铁氧体纳米颗粒已被证实可用于去除水体中的重金属与类金属；而稀释悬浮的钴铁氧体纳米颗粒则在医学领域展现出良好的应用前景。然而，这类纳米颗粒广泛暴露所带来的潜在毒理学影响仍未明确。由于钴铁氧体纳米颗粒被视为环境或医学应用后的残留废弃物，人类或其他生物食用相关植物后，植物可能成为工程化纳米材料进入机体的途径。因此，本研究旨在评估干粉与新鲜钴铁氧体纳米颗粒对小麦植株的影响。本研究以石英砂作为植物生长基质，开展了为期7天的试验。所测定的毒性终点包括种子萌发率、根长与株高、钴（Co）与铁（Fe）的总积累量、光合色素含量、蛋白质（PRT）含量，以及过氧化氢酶（CAT）、抗坏血酸过氧化物酶（APX）与愈创木酚过氧化物酶（GPX）的活性。植株组织中Co与Fe总含量的升高，表明小麦植株已接触钴铁氧体纳米颗粒。种子萌发率与株高并非足够灵敏的毒性终点。使植株根长降低50%的半数有效浓度（EC₅₀）分别为：新鲜铁氧体纳米颗粒1963 mg/kg，干粉铁氧体纳米颗粒5023 mg/kg。由此可见，新鲜铁氧体纳米颗粒的毒性高于干粉纳米颗粒。光合色素的显著降低表明植株受到胁迫。CAT、APX与GPX的抗氧化酶活性提示，钴铁氧体纳米颗粒可诱导活性氧的产生并引发氧化损伤。因此，仍需开展更多研究以明确使用这类纳米颗粒的收益是否大于其潜在风险。