Antibacterial ZnO nanoparticle embedded polycaprolactone—polyhydroxybutyrate membranes for wound healing

Wound management remains a significant clinical challenge, driving the development of multifunctional biomaterials that combine mechanical integrity, antibacterial activity, and biocompatibility. In this study, polycaprolactone-polyhydroxybutyrate (PCL-PHB) composite membranes incorporating zinc oxide nanoparticles (ZnO NPs) were fabricated via a solvent-casting approach and systematically optimised for wound-healing applications. ZnO NPs were incorporated at varying loadings (0.5-2 wt%), and the resulting membranes were characterised for morphology, chemical structure, crystallinity, surface wettability, mechanical performance, antibacterial efficacy, and cytocompatibility. FTIR, XRD, FESEM, and EDX analyses confirmed successful integration of ZnO nanoparticles within the PCL-PHB matrix, while FESEM observations suggested relatively uniform nanoparticle dispersion at lower ZnO concentrations. Incorporation of ZnO NPs significantly enhanced tensile strength and antibacterial performance, with optimal properties observed at intermediate nanoparticle loadings (1-1.5 wt%). Nanoparticle incorporation enhanced tensile strength from 2.0 MPa for the control membrane to a maximum of 4.8 MPa at 0.5 wt% ZnO loading. Higher ZnO concentrations led to nanoparticle aggregation and a decline in mechanical properties. The composite membranes exhibited pronounced antibacterial activity of about 90% against Staphylococcus aureus and moderate activity against Pseudomonas aeruginosa (32.5%). Importantly, all ZnO-containing membranes demonstrated high cytocompatibility with THP-1 monocyte-derived immune cells, maintaining cell viability above 80% and preserving normal cytoskeletal organisation. These findings highlight the importance of nanoparticle loading optimisation and nanoscale dispersion in the design of multifunctional antibacterial polymer nanocomposites for wound management.