Chitosan as a wall biomaterial for the encapsulation of essential oils: A comprehensive review of pharmaceutical breakthroughs and future directions.

The use of natural biopolymers has recently gained significant attention across various fields. Although various biopolymer essential oil (EO)-based formulations have been produced, the extensive use of these formulations on an industrial scale remains limited, possibly due to limitations such as high volatility, low stability, bioavailability, poor solubility, susceptibility to oxidation, and aroma effects. Thus, incorporating EOs into food products as emulsions, films, and coatings is challenging. Meanwhile, chitosan (CS), a widely utilized biopolymer, serves as an effective encapsulating agent that protects biomolecules from environmental and processing factors. Therefore, CS represents an ideal candidate for encapsulating EOs, either alone or in combination with other polymers. This review provides a brief history of CS, the production, structure, properties, and various modifications to improve the properties of CS. Additionally, this review explores the biosynthetic pathways of EOs, highlighting the specialized cellular mechanisms in aromatic plants, including enzymatic and genetic factors that contribute to the production of EOs. Moreover, this review explores the antibiotic resistance of a CS-EO combination through a mechanistic approach for antibacterial, antifungal, antioxidant, wound healing, and anticancer activities. Furthermore, this review projects the transformative impact of integrating nanotechnology and nanoencapsulation in the controlled delivery of EO antioxidants and imaging agents. Ultimately, this review aims to deliver valuable insights into the developments, challenges, and further investigations that must be conducted to optimize formulation scalability and discover clinical applications of EO nanoscale materials in pharmaceutical therapies.