Polyhydroxybutyrate nanoparticles for encapsulating carvacrol: release in food simulants, antimicrobial applications...

Biological food contamination is a serious public health and economic problem worldwide. Antibiotics are commonly used to address this issue, but rising bacterial resistance has sparked interest in natural alternatives, such as carvacrol. Carvacrol (CAR), a bioactive compound in oregano and thyme essential oils, has demonstrated potent antimicrobial properties. However, its high volatility and environmental sensitivity limit direct application in food systems, requiring encapsulation strategies to enhance stability and controlled release. This study aimed to develop and characterize polyhydroxybutyrate nanoparticles (CAR-PHB-NPs) encapsulating carvacrol for enhanced stability, antimicrobial activity, and controlled release behavior. Nanoparticles were synthesized via nanoprecipitation, yielding hydrodynamic diameters of 200-250 nm, polydispersity index values of 0.220-0.327, and zeta potential values of -25 to -43 mV, ensuring colloidal stability. Storage tests confirmed refrigeration-maintained nanoparticle stability for over 247 days. Among the tested formulations, 25%CAR-0.2%PHB-NPs exhibited the highest encapsulation efficiency (15.56%). Release kinetics studies demonstrated prolonged release, particularly in non-polar solvent systems simulating moderate and lipid-rich matrices. The antimicrobial activity of CAR-PHB-NPs was confirmed against Staphylococcus aureus and Listeria monocytogenes, with inhibitory effects of 0.76 log (CFU/mL) and 0.56 log (CFU/mL), respectively. Additionally, cytotoxic assay in A549 human lung epithelial cells revealed a dose-dependent reduction in cell viability, moderate concentrations maintaining viability above 50%, suggesting balance between biocompatibility and functional anticancer activity. Overall, CAR-PHB-NPs demonstrated a promising role in food preservation and biomedical applications by ensuring sustained antimicrobial activity and controlled cytotoxic effects. Future research should optimize formulations, assess gastrointestinal absorption mechanisms, and explore targeted drug delivery applications.