Exploring the Synergy of Metallic Antimicrobial Agents in Ternary Blends of PHB/PLA/PCL

Abstract

This study provides a comprehensive investigation of antimicrobial additives (ZnO/AgNPs and SiO₂/AgNPs) on the properties of biodegradable ternary blends composed of poly(hydroxybutyrate) (PHB), poly(lactic acid) (PLA), and polycaprolactone (PCL) by examining the morphology, thermal stability, crystallinity index, and cell viability of these blends. Overall, transmission electron microscopy (TEM) analysis revealed that AgNPs and SiO₂ exhibited comparable sizes, whereas ZnO was significantly larger, which influences their release profiles and interactions with the blends. The addition of antimicrobials influences the rheology of the blends, acting as compatibilizers by reducing the intermolecular forces between biopolymers. Scanning electron microscopy (SEM) analysis revealed a matrix–core–shell structure, indicating enhanced interfacial interaction among the immiscible biopolymers, as predicted by their spreading coefficient. From thermal evaluations, PCL promotes overall thermal stability, where T₅ (the temperature at which the sample loses 5% of its weight through thermal degradation) was more than 22% higher than T₅ of blends, and the antimicrobials investigated tend to act as barriers to heat penetration, thereby influencing the degradation mechanism of the blends. Additionally, antimicrobials tend to increase material crystallinity, suggesting their nucleating effect. Both PLA and PCL have shown high viability for cell growth and proliferation. The 30/50/20 (PHB/PLA/PCL wt%) blends were conducive to cell adhesion and proliferation, achieving cell viability rates up to 85% irrespective of the antimicrobial concentration. SEM analysis also confirmed the presence of viable cells and attachment of organic cell structures over the surface of the produced materials. In conclusion, this study highlights the potential of biodegradable ternary blends containing antimicrobial NPs, particularly for use in medical devices such as ureteral stents.