Synthesis of chitosan-encapsulated mono- and di-metallic (Zn/Ca) MOFs to modulate seed quality and antioxidant defense in Chenopodium quinoa under salinity stress

Soil salinity is a major environmental constraint that severely limits the growth and nutritional yield of Chenopodium quinoa Willd. Although metal-organic frameworks (MOFs) show strong potential in agricultural settings, hybridizing them with biopolymers facilitates application under environmental conditions. This study aimed to develop a novel biostimulant by synthesizing chitosan-encapsulated mono-metallic (Zn-MOF) and di-metallic (Zn/Ca-MOF) frameworks and evaluating their efficacy in quinoa under saline field conditions. The composites were synthesized and characterized for their structural and chemical properties. Quinoa plants were cultivated under saline field conditions and treated with chitosan-MOF composites to assess physiological and biochemical responses, with a focus on nutritional value and the antioxidant defense system. Our findings revealed that application of the chitosan-MOF composites-most notably the bimetallic Zn/Ca formulation-substantially enhanced plant growth, biomass accumulation, and physiological performance under saline field conditions. Treatment with the composite enhanced the accumulation of key nutritional constituents in the seeds, specifically increasing the relative proportions of phytosterols, unsaturated fatty acids, and essential amino acids. Furthermore, application of the composite enhanced antioxidant enzyme activities (including SOD and POD), which was accompanied by a marked reduction in lipid peroxidation (45%) and hydrogen peroxide levels (57%). These physiological improvements corresponded to significant gains in plant biomass and seed quality parameters under saline field conditions. Overall, this study demonstrates that chitosan-encapsulated di-metallic frameworks serve as an effective, multi-functional strategy for enhancing salt tolerance in quinoa, offering a sustainable approach to improving crop resilience and food security in saline environments.