Exploiting the synergistic influence of AgNPs-TiO2NPs: enhancing phytostabilization of Pb and mitigating its toxicity in Vigna unguiculata.

Abstract

In this study, a composite of silver and titanium dioxide nanoparticles (AgNPs-TiO₂NPs) was examined for its synergistic effects on phytostabilization of lead (Pb) and mitigation of toxicity in cowpea (Vigna unguiculata (L) Walp). Seeds of V. unguiculata were wetted with water, 0.05 and 0.1 mgL^-1 Pb and 25 mgmL^-1 each of AgNPs, TiO₂NPs, and AgNPs-TiO₂NPs. Root lengths of V. unguiculata were reduced by 25% and 44% at 0.05 and 0.1 mgL^-1 Pb, respectively, while shoot lengths were reduced by 2% and 7%. In V. unguiculata, AgNPs and TiO₂NPs significantly improved physiological indicators and mitigated Pb effects, with TiO₂NPs modulating physiological parameters more effectively than AgNPs. The composite (AgNPs-TiO₂NPs) synergistically regulated V. unguiculata physiology better than individual nanoparticles. Compared to individual AgNPs and TiO₂NPs, the composite (AgNPs-TiO₂NPs) synergistically increased antioxidant activity by 12% and 9%, and carotenoid contents by 88%. Additionally, AgNPs-TiO₂NPs effectively reduced malondialdehyde levels by 29%, thereby mitigating the effects of Pb on V. unguiculata better than individual nanoparticles. AgNPs-TiO₂NPs enhanced Pb immobilization by 57%, reducing its translocation from soil to shoots compared to V. unguiculata wetted with water. The bioconcentration and translocation factors of Pb indicate that phytostabilization was most effective when the composite was used.