Role of Stearic Acid toward the Gelation of Cocoa Butter and Wheat Germ Oil-Based Oleogels: Preparation, Physical Properties, and Application in Topical Mupirocin Delivery

Abstract

Oleogel (OG) is one of the popular sources of unsaturated fatty acids that replace hazardous saturated fatty acids, synthesized by structuring edible oils using gelators. In our present investigation, we prepared OGs by varying the ratios of cocoa butter (CB), wheat germ oil (WGO), and a fixed amount of stearic acid (SA) for topical drug delivery application. The critical gelation concentration of CB in WGO was found to be 3% (w/w) in the presence of 7.75% (w/w) SA. Various characterization techniques were employed for the developed OGs, including bright-field and polarized light microscopy, crystallization kinetics, X-ray diffraction (XRD), and rheology. Micrographs captured by using polarized light and brightfield microscopes illustrated the crystalline structure of the OGs. OGs displayed a network of needle-shaped arrangements due to the presence of SA and CB. XRD results demonstrated the formation of a β′ polymorph structure inside the OG and rheological data proves that the OG formulation with 20% (w/w) CB (OG 20) forms the strongest OG among all formulations. Moreover, the crystallization kinetics was studied to observe the development of solid fat crystals in OGs. The in vitro release of mupirocin from the OGs was best described by the Korsmeyer−Peppas and Peppas−Sahlin models, indicating that drug diffusion occurred via Fickian mechanism. Additionally, OGs were investigated and explored for potential topical drug delivery applications through ex vivo permeation studies.