Polymeric nanoparticles for enhanced delivery and improved bioactivity of essential oils

Essential oils are volatile constituents that give aromatic plants their characteristic odour. The application of these plant actives in food, agriculture, pharmaceutics, and cosmetics has been widely studied. Aromatherapy, a complementary therapy involving the use of essential oils to treat several diseases ranging from microbial infections to metabolic dysfunctions, has been utilised for centuries. Anticancer, antimicrobial, and anti-inflammatory activities are well-established among other pharmacological properties of these aromatic oils. The oils, which are composed mainly of terpene-based compounds, have also been explored as nutraceuticals, alternative green preservatives, and functional additives in foods. However, due to their physicochemical properties, viz high volatility and low aqueous solubility, essential oil delivery to target receptors were challenging when administered as chemotherapeutics. Hence, formulating essential oils with suitable excipients to enhance their delivery and bioavailability, invariably improving their bioactivity and therapeutic efficacy becomes expedient. Nanotechnology presents a unique strategy to develop a particulate delivery system for the controlled, sustained, and extended release of essential oils. In this review, we examine and summarize the trends and developments in the formulation of essential oils using polymeric nanoparticles.