Preparation of Temperature-Sensitive Oleogels for the Controlled Release of Exocarpium citri grandisis Essential Oil in Oral Cavity

A novel Exocarpium citri grandisis essential oil (EEO) oleogel was designed to obtain a temperature-sensitive and sustained release system with beeswax in this study. With the increasing beeswax concentration (12, 14, 16, and 18% w/w), a more dense needle-like morphology was formed by the network of beeswax crystals within the EEO. EEO oleogels with higher beeswax content exhibited greater thermal stability due to the physical interactions between molecules, including van der Waals and hydrogen bonding, and there was no chemical interaction between EEO and beeswax according to structural analysis. Moreover, the higher beeswax concentration led to stiffer EEO oleogels with higher yield stress. EEO oleogels with 14% beeswax allowed for the burst release of EEO at 37 °C. This study provided a simple and new controlled release system for EEO, which could be slowly released in the oral cavity to directly exert its cough-relieving effect.