Formulation of Gelled Microemulsion for Effective Permeation of Celecoxib Across the Skin Barrier

Abstract Microemulsion‐based gels (μEGs) are smart colloidal carriers, superior to traditional topical formulations due to formulation simplicity, structural flexibility, high stability, and controlled delivery of topical drugs through biofilms. Here, we report a new μEG formulation for topical application of an anti‐inflammatory drug, celecoxib (CXB). For this, the μE system was formulated using olive oil (~10 %), Water (~15 %), Tween‐80 (~67.5 %) and Span‐80 (~7.5 %) to enhanced the loading of CXB (~2.0 wt.%), and then gelled to semisolid μEG by the addition of polyethylene glycol 6000 (PEG‐6000) (2.0 wt.%) to modulate CXB passage across the skin‐barriers. Optical microscopy showed the transition from water‐in‐oil (w/o) to oil‐in‐water (o/w) through bicontinuous networks. Dynamic light scattering and electron micrographs demonstrate very fine unimodal assembly of CXB‐μE nanodroplets (~65 nm), which didn't amalgamate to form spherical CXB‐μEG (~95 nm) after gelation. Moreover, FTIR analysis showed effective encapsulation of CXB into hydrophobic microenvironment with no observable chemical interaction between CXB and μE excipients, which was further verified by the peak‐to‐peak measurement of fluorescence. Further, ex‐vivo permeation of CXB‐μEG showed enhanced and persistent permeation (>99 %) within 10 hours at pH=5.5 into rabbit skin barrier. This demonstrates the sustained release of CXB in μEG and the enhancement in transdermal delivery over its conventional topical formulations.