Self-assembled Trehalose Amphiphiles as Molecular Gels: A Unique Formulation to Wax-free Cosmetics

Trehalose has been used as an emollient and antioxidant in cosmetics. However, we aimed to explore trehalose amphiphiles as oil structuring agents for the preparation of gel-based lip balms as part of wax-free cosmetics. This article describes the synthesis of trehalose fatty acyl amphiphiles and their corresponding oleogel-based lip balms. Trehalose dialkanoates were synthesized by esterifying the two primary hydroxyls of trehalose with fatty acids (C4-C12) using a facile, regioselective lipase catalysis. The gelation potential of as-synthesized amphiphiles was evaluated in organic solvents and vegetable oils. Stable oleogels were subjected to X-ray diffraction (XRD), thermal (DSC), and rheological studies and further used for the preparation of lip balms. Trehalose dioctanoate (Tr8), trehalose didecanoate (Tr10) were found to be super gelators as their minimum gelation concentration is ≤ 0.2 wt%. XRD studies revealed their hexagonal columnar molecular packing while forming the fibrillar networks. Rheometry proved that the fatty acyl chain length of amphiphiles can influence the strength and flow properties of oleogels. Further rheometry (at 25 °C, 37 °C, and 50 °C) and DSC studies have validated that Tr8- and Tr10-based oleogels are stable for commercial applications. Tr8- and Tr10-based olive oil oleogels were used for the preparation of lip balms. The preliminary results suggested that the cumulative effect of trehalose's emolliency and vegetable oil gelling nature can be achieved with trehalose amphiphiles, specifically, Tr8 and Tr10. This study has also demonstrated that Tr8- and Tr10-based lip balms can be used as an alternative to beeswax and plant wax lip balms, indicating their huge potential to succeed as a new paradigm to formulate wax-free cosmetics.