Well-Dispersed AgNP Immobilization on APTES-Modified Zinc Silicate Glass for Durable Antibacterial PLA Composites

Zinc silicate glass powder (ZS) is an inorganic antibacterial filler that releases zinc ions while improving surface hydrophilicity. Silver nanoparticles (AgNPs) possess strong antibacterial properties through direct contact with bacterial cells and the continuous release of silver ions. In this study, ZS was incorporated into a polylactic acid (PLA) matrix to develop biodegradable antibacterial composites, and AgNPs were immobilized onto either pristine ZS or APTES-functionalized ZS to prepare Ag@ZS and Ag@aZS fillers, respectively. The incorporation of ZS provided PLA composites with effective antibacterial activity against Escherichia coli. Furthermore, the introduction of Ag@ZS and Ag@aZS markedly enhanced antibacterial performance against both E. coli and Staphylococcus aureus, even at low filler loadings. Surface functionalization with APTES promoted a more uniform and stable immobilization of AgNPs on the ZS surface, resulting in higher silver loading and stronger interfacial interactions with the PLA matrix. These improvements led to enhanced mechanical performance and optical transparency while maintaining excellent antibacterial activity over an extended period. The results demonstrate that APTES-assisted AgNP immobilization is an effective strategy for producing multifunctional PLA composites with high antibacterial efficiency, good mechanical integrity, and long-term durability, making them promising candidates for sustainable antibacterial plastic applications.