Human risk assessment of lead toxicity in maize: a novel approach using TiO2- and MgO-nanoparticles

Abstract

Nanotechnology is capturing great interest worldwide owing to their stirring applications in various fields. In particular, individual applications of titanium dioxide-nanoparticles (TiO₂-NPs) and magnesium oxide-nanoparticles (MgO-NPs) have been extensively studied. However, the combined application of TiO₂- and MgO-NPs is a novel approach and has been explored in only a few studies. This study was conducted considering the positive effects of TiO₂- and MgO-NPs in reducing lead (Pb) toxicity in plants. A pot experiment was conducted to determine the effects of single and/or combined application of different levels [25 and 50 μM L⁻¹] of TiO₂- and MgO-NPs on Pb accumulation and morpho-physio-biochemical attributes of maize (Zea mays L.), which was exposed to severe Pb stress [0 (without Pb stress) to 100 mg kg⁻¹]. The research outcomes indicated that elevated levels of Pb stress in the soil significantly (P ≤ 0.05) decreased plant growth and biomass, photosynthetic pigments, and gas exchange parameters. However, Pb stress also triggered oxidative stress in the plants by increasing malondialdehyde (MDA) and hydrogen peroxide (H₂O₂), health risk index (HRI), and also defected cellular organelles which were observed under scanning electron microscope (SEM), which also induced increased compounds of various enzymatic and non-enzymatic antioxidants and also the gene expression and sugar content. Furthermore, a significant (P ≤ 0.05) increase in proline metabolism and the ascorbate–glutathione (AsA–GSH) cycle was observed. The application of TiO₂- and MgO-NPs showed a significant (P ≤ 0.05) increase in plant growth and biomass, gas exchange parameters, and enzymatic and non-enzymatic compounds and their gene expressions, and it decreased the oxidative stress. In addition, the application of TiO₂- and MgO-NPs enhanced cellular fractionation and decreased the proline metabolism and AsA–GSH cycle in Z. mays plants. These results offer new insights for sustainable agriculture practices and hold immense promise in addressing the pressing challenges of heavy metal contamination in agricultural soils.