Functional alginate-chitosan packaging nanofilms enhanced with calcium chloride and in situ synthesized ZnO@MgO nano-heterostructures

Abstract

The use of biodegradable materials in food packaging has gained increasing attention as a sustainable alternative to conventional plastics. In this study, calcium chloride-loaded nanofilms were developed using sodium alginate (NaAlg) as the primary polymer matrix, with chitosan (Ch) added at varying concentrations, resulting in three formulations (NF1–NF3). The films were further reinforced with bimetallic ZnO@MgO nanoparticles to enhance functionality. Comprehensive characterization was conducted to evaluate structural, morphological, thermal, and mechanical properties. FTIR analysis confirmed strong interactions between NaAlg and Ch, indicating successful formation of a blended polymer network, while characteristic bands verified nanoparticle incorporation. SEM observations showed that increasing chitosan content resulted in denser, rougher film surfaces, suggesting enhanced intermolecular interactions. Thermal analysis demonstrated improved stability of the nanofilms compared to neat polymers, likely due to crosslinking effects and the presence of inorganic nanoparticles. Mechanical testing revealed enhanced tensile properties across all formulations compared with pure alginate films. Biocompatibility assessment using Vero and Wi-38 cell lines confirmed low cytotoxicity, with cell viability remaining above safe limits. Antimicrobial activity significantly increased with higher chitosan and nanoparticle content, with NF3 showing the strongest inhibition against the tested microorganisms. Additionally, antioxidant activity improved progressively, reaching 87.50% in NF3. Moreover, biodegradation of the formulated films in soil was rapid. Calcium and bimetallic ion migration test exhibited controlled release in the food simulation system. In conclusion, the developed alginate–chitosan nanofilms reinforced with ZnO@MgONPs exhibited enhanced physicochemical, mechanical, antimicrobial, and antioxidant properties, highlighting their strong potential as safe and effective biodegradable materials for active food packaging applications.