Green Synthesis of Selenium Nanoparticles by Grape Seed Extract Synergized with Ascorbic Acid: Preparation Optimization, Structural Characterization, and Functional Activity

Selenium nanoparticles (SeNPs) have broad application prospects in food preservation and drug development. In this study, grape seed extract (GSE) was used as a natural reducing agent and stabilizer, combined with ascorbic acid (Vc) for the green synthesis of SeNPs (GSE-SeNPs). The preparation process and structural stability were systematically optimized. Response surface methodology (RSM) was employed to optimize the concentrations of Vc and GSE, reaction time, and reaction temperature, aiming to screen out the optimal synthesis conditions with small particle size, good dispersibility, and the smallest PDI value. The results showed that the average particle size of GSE-SeNPs was 74.86 ± 6.07 nm, the PDI was 0.159 ± 0.028, and the Zeta potential was -30.42 ± 0.54 mV, indicating good stability. Characterization results revealed that GSE participated in the reduction and stabilization of SeNPs through electrostatic interactions and hydrogen bonds, forming spherical nanoparticles with a dense structure and good surface organic coating. In addition, GSE-SeNPs exhibited excellent DPPH free radical scavenging ability and antibacterial activity against <i>Staphylococcus aureus</i> in vitro. GSE-SeNPs combine green synthesis, structural stability, and multifunctional biological activities, and have the potential to be used as functional nanomaterials in food preservation and safety fields.