Successive nitric oxide and lipoic acid priming mitigates [ZnO]NPs toxicity in wheat: experimental and DFT insights

The global food security is threatened by the accumulation of anthropogenic nanomaterials in the environment. We investigated the phytotoxic effects of elevated zinc oxide nanoparticles ([ZnO]NPs: 300-400 mg L⁻¹) on wheat (Triticum aestivum L.) and evaluated a novel detoxification strategy using successive redox-priming. Wheat caryopses were primed with alpha-lipoic acid (LA) and sodium nitroprusside (SNP, a nitric oxide donor) either individually or in successive sequences (LA→SNP and SNP→LA). Exposure to [ZnO]NPs resulted in significant growth inhibition, reduction of biomass and degradation of chlorophyll. However, successive priming, particularly the LA+SNP combination, significantly attenuated these negative effects. This treatment effectively restored seedling growth by creating a strong antioxidant shield, greatly increasing the activities of SOD, POD, CAT, and APX, and raising metal chelating activity to 98.1%. Furthermore, Density Functional Theory (DFT) calculations, including HOMO-LUMO and molecular electrostatic potential (MEP) analyses, gave mechanistic insights into the molecular interactions of the priming agents and ZnO, highlighting their role as potent radical scavengers and stabilizers. The results indicate that a successive redox priming is an effective and sustainable approach to enhance crop tolerance to high concentrations of nanoparticle toxicity.