Essential Oil Nano-Delivery Systems: Recent Developments and Emerging Applications

Essential oils (EOs) are aromatic compounds of plant origin with several bioactive properties. The current global essential oil production exceeds 300,000 tonnes, and the estimated EO market size in 2030 is approximately $ 39.5 billion USD. Such compounds undergo degradation upon exposure to environmental stresses during processing and storage. The nanocarrier systems primarily protect EO from environmental conditions, and the EO nanoformulations have demonstrated better performance compared to their free counterparts. For example, studies have reported a 2- to 9-fold increase in bioactivity, improved stability, and controlled release that extends from hours to days. The present review article is focused on the current state of knowledge of different advanced applications mediated through several nanoformulations of EO, such as nanoemulsions, nanoparticles, nanofibers, nanocapsules, nanoencapsulation, and nanoliposomes. The encapsulation efficiency of the formulations reaches up to 99% depending on the type of EO and the type of nanoformulation. It was seen that the usage of starch-based nanoformulation further enhances the nano-EO incorporation in aqueous matrices. Thereafter, the mechanism of action and release kinetics of EO nanoformulations are briefly discussed. Finally, the paper concludes with highlights on limitations that are frequently encountered, while emphasising the adaptability of nanoformulations for the target delivery of EO. Hence, the readers of this paper will gain a comprehensive knowledge through the information gathered from the literature of the latest years that will help advance future research on the safety evaluation, biodegradation, and long-term effects of the EO nanoformulation.