Alleviation of Salinity Stress by Ternary Se/CuO/ZnO Nanocomposite Synthesis by Urtica urens Biomass and their Antioxidant, Cytotoxic Properties

Abstract

Salinity stress is a major environmental constraint that adversely affects plant growth and their productivity. In this work, ternary selenium/copper oxide/zinc oxide nanocomposite (Se/CuO/ZnO NCs; TSCZ NCs) were synthesized for the first time using aqueous leaf extract of Urtica urens and evaluated for their ability to alleviate salinity stress in Eruca sativa plants. The synthesized nanoparticles were characterized using TEM, SAED, EDX, and XRD analyses, which confirmed the formation of predominantly spherical crystalline nanoparticles (average size of 58.71 ± 3.58 nm) and distinct elemental composition of Se, CuO, and ZnO. A pot experiment was conducted under normal and saline conditions (100 mM NaCl) using different concentrations of TSCZ NCs (up to 200 ppm). Salinity stress significantly reduced shoot and root growth, photosynthetic pigments, carbohydrate and protein contents, while increasing proline accumulation, antioxidant enzyme activities, and lipid peroxidation. Foliar application of TSCZ NCs partially mitigated these adverse effects, particularly at 100 ppm. The nanoparticles also modulated antioxidant defense enzymes in treated plants. In addition, TSCZ NCs exhibited strong antioxidant activity in the DPPH assay, reaching 89.4% scavenging at 1000 µg/mL, and demonstrated low cytotoxicity toward Vero normal cell lines. These findings suggest that Se/CuO/ZnO NCs may represent a promising nano-enabled strategy for improving salinity tolerance in plants.