Hydrothermal Synthesis of Silver Nanoparticles and their Application as a Functionalizing Agent for Chitosan–Vanillin Film

Abstract

Perishable fruits and vegetables are highly susceptible to postharvest losses, driving the search for sustainable biopolymer-based packaging. Nevertheless, limited mechanical properties and lack of active functionalities remain major challenges. Here, we address these limitations by developing chitosan-vanillin films loaded with hydrothermally synthesized silver nanoparticles (AgNPs). AgNPs were characterized by UV–vis, DLS, NTA, AFM, SEM-EDS and FTIR, while chitosan acts as reducing agent and vanillin builds a Schiff-base network providing mechanical reinforcement and antioxidant activity. Antimicrobial testing relied on a contact-based viability assay, providing quantitative time-resolved data representative of real packaging conditions. AgNPs reduced viable populations of Escherichia coli (88.4–90.7% within 3 h) and Staphylococcus aureus (71.5% after 24 h), with no regrowth in loaded films. Vanillin increased DPPH and ABTS inhibition 4- and 7-fold, respectively, whereas AgNPs incorporation delayed moisture transmission by up to 17.4 h. These findings highlight chitosan-vanillin-AgNPs films as a promising candidate for sustainable active food packaging.