Nano-selenium functionalized sodium alginate/pectin film with dual enzyme-like activity for antioxidant preservation of postharvest strawberries

Sodium alginate/pectin (SP) composite film functionalized with Nano-selenium (SeNPs) stabilized with Dendrobium officinale polysaccharides (DOP) was developed to enhance its physicochemical and biological activity properties. The addition of DOP significantly improved the dispersibility and surface potential of SeNPs, and the nanoparticles stabilized with 100% DOP exhibited the smallest particle size (210.45 nm), highest zeta potential (-7.95 mV), and optimal superoxide dismutase (SOD) and catalase (CAT) -like activities. Adding 2% SeNPs to SP film improved UV-blocking performance, matrix density, and thermal stability, as well as extensibility and barrier performance. Among the various formulations, SPS-2 film (SP film ccontaining 2% SeNPs) exhibited the highest antioxidant and antibacterial activity, effectively inhibiting Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) . The high-concentration SeNPs composite film demonstrated high biocompatibility, exhibiting no hemolytic activity against red blood cells and minimal cytotoxicity against RAW 264.7 cells. In a postharvest strawberry preservation test, the SPS-2 coating effectively reduced weight loss and spoilage, maintained firmness and soluble solids, and significantly enhanced antioxidant activity by preserving total phenol and flavonoid content. These results demonstrate that 2% SeNPs-added SP films provide an integrated strategy combining enzyme-mimetic activity, enhanced film performance, and high biosafety, and show promising potential for postharvest fruit preservation.