TiO2 nanoparticles reprogram cellular metabolism to mitigate UV-B-induced oxidative stress in lettuce

Titanium dioxide (TiO 2 ) nanoparticles (NPs) represent a promising nanobiotechnology approach for enhancing plant resilience to environmental stressors. This study elucidated the molecular mechanisms underlying TiO 2 NPs protect lettuce ( Lactuca sativa L. var. crispa) from UV-B radiation. The lettuce was grown under controlled conditions and exposed to supplemental UV-B irradiation. Using TiO 2 NP concentrations of 0, 100, and 200 mg/L under controlled UV-B exposure, we investigated plant stress responses through interactions at the nano-bio interface. TiO 2 NP treatment orchestrated a comprehensive cellular defense mechanism through modulation of specific antioxidant enzyme networks. The activity of superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase were enhanced, resulting in a significant reduction in the oxidative stress markers, hydrogen peroxide and malondialdehyde. This antioxidant activation was coupled with TiO 2 NP-mediated enhancement of photosynthesis as evidenced by higher electron transport rates and net photosynthesis levels, particularly at the 200 mg/L concentration. TiO 2 NPs treatment triggered coordinated metabolic reprogramming, simultaneously upregulating photoprotective pigments (chlorophyll b and carotenoids) and stress-responsive secondary metabolites (flavonoids and anthocyanins). This multi-layered protection system demonstrated quantifiable physiological benefits, with complete restoration of shoot biomass under UV-B stress conditions. Our data demonstrate that TiO 2 NPs act as multifunctional stress-mitigating agents through precise modulation of cellular redox homeostasis and photosynthetic efficiency. This nanomaterial approach offers significant potential for engineering effective methods of next-generation crop protection and sustainable agriculture in high-UV environments. • TiO 2 NPs enhance the activity of antioxidant enzymes, thereby mitigating UV-B oxidative stress. • TiO 2 NPs promote the accumulation of flavonoids, anthocyanins, and proline for UV protection. • TiO 2 NPs stabilize pigments, improve electron transport, and optimize photosynthesis. • Foliar TiO 2 NPs restore shoot biomass and growth under UV-B stress. • Responses vary by cultivar, reflecting differences in antioxidant and metabolite profiles.