PEI-coated PLA nanoparticles to enhance the antimicrobial activity of carvacrol

Carvacrol (CAR) is a natural bioactive compound with antioxidant and antimicrobial activity that is present in essential oils. The application of CAR in food preservation is hampered by its high volatility, low solubility in water, and susceptibility to light, heat and oxygen degradation. Polylactide (PLA) is an FDA-approved polymer derived from renewable resources. Controlled release of CAR from PLA nanoparticles (NPs) could improve its antimicrobial efficacy and storage. In this study, negatively charged CAR-NPs and positively charged polyethylenimine (PEI)-coated CAR-(PEI)NPs were formulated by nanoprecipitation methods and characterised by dynamic light scattering, electron microscopy, encapsulation efficiency, and drug loading capacity. The positively charged (PEI)NPs enhanced the in vitro antimicrobial activity of CAR against Escherichia coli, Listeria monocytogenes, Salmonella enterica and Staphylococcus aureus. Bacterial uptake, evaporation tests, release studies and NP stability after storage were assessed to provide evidence supporting CAR-(PEI)NPs as a potential nanocarrier for further development in food preservation.