Toxicity assessment of zinc oxide nanoparticles on seed germination, soil bacteria, and mammalian cells

Zinc oxide nanoparticles (nano-ZnO) are extensively used in commercial applications due to their antimicrobial, UV-blocking, and catalytic properties. Recently, they have been evaluated as nutrients to enhance plant growth. However, insufficient data exists on their toxicological effects, particularly in agricultural settings. This study aims to investigate the toxicity of nano-ZnO on seed germination, soil microorganisms, and mammalian cells (human lung fibroblast cells - MRC5). Nano-ZnO was synthesized using zinc nitrate hexahydrate, sodium hydroxide, and soluble starch as stabilizers, and characterized using various techniques. Seed germination assays were performed on wheat (Triticum aestivum), green gram (Vigna radiata), cowpea (Vigna unguiculata), and chickpea (Cicer arietinum). The minimum bactericidal (MBC) and inhibitory concentrations (MIC) of nano-ZnO were tested against soil bacteria such as Pseudomonas aeruginosa, P. putida, Bacillus megaterium, and Pantoea agglomerans. The study also assessed the impact on yeast, algae, and the viability of MRC5 fibroblast cells using the MTT assay. The results provide essential insights for the safe use of nano-ZnO in agriculture.