Sargassum latifolium-mediated Se/CuO/MgO/ZnO nanocomposite enhances salt tolerance in Phaseolus vulgaris and exhibits antibacterial and antioxidant activities

Abstract

Abstract Macroalgae represents a powerful, renewable bioplatform for generating high-performance nanomaterials that bridge sustainability with advanced biotechnological applications. However, crop production and multi-drug resistance microbes are considered the main challenge worldwide. Also, the incorporation of macroalgae metabolites to generate multimetallic nanocomposite, as a new active compound, remains unexplored. In this work, the brown macroalga Sargassum latifolium was exploited as a robust biofactory for the green fabrication of multifunctional active tetrametallic Se/CuO/MgO/ZnO (TSCMZ) nanocomposite. The biosynthesized TSCMZ were characterized by FT-IR which explains the role of different algal-active metabolites in biofabrication process. Also, TEM, SAED, and EDX confirm the spherical shape with average sizes of 24   nm and the presence of metallic elements as main nanocomposite component. Polycrystalline architecture of synthesized nanocomposite was confirmed by XRD analysis. Under field conditions, Phaseolus vulgaris L. exposed to 100 mM NaCl experienced drastic impairments in growth, metabolism, and yield stability. Remarkably, foliar application of TSCMZ (50–200 ppm), especially at 200 ppm, significantly mitigate salt stress, elevating metabolic performance, and recovering key yield attributes. This enhancement was accompanied by substantial increases in chlorophylls (a, b, and a + b), carotenoids, free proline, carbohydrate and protein biosynthesis, indicating strengthened osmotic adjustment and redox homeostasis. Beyond its agronomic impact, TSCMZ displayed striking antibacterial potency, with low MIC values (12.5–25 µg mL –1 ) against multidrug-resistant (MDR) pathogens including E. coli and Klebsiella pneumoniae . Moreover, the algal-mediated tetrametallic nanocomposite demonstrated high antioxidant strength through potent DPPH radical scavenging at ≥ 125 µg mL –1 . Collectively, these findings demonstrate that TSCMZ is a salt-stress mitigation treatment and have the efficacy to inhibits the growth of MDR bacterial strains.