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

Microemulsion-based gels (mu EGs) 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 mu EG formulation for topical application of an anti-inflammatory drug, celecoxib (CXB). For this, the mu E system was formulated using olive oil (similar to 10 %), Water (similar to 15 %), Tween-80 (similar to 67.5 %) and Span-80 (similar to 7.5 %) to enhanced the loading of CXB (similar to 2.0 wt.%), and then gelled to semisolid mu EG 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-mu E nanodroplets (similar to 65 nm), which didn't amalgamate to form spherical CXB-mu EG (similar to 95 nm) after gelation. Moreover, FTIR analysis showed effective encapsulation of CXB into hydrophobic microenvironment with no observable chemical interaction between CXB and mu E excipients, which was further verified by the peak-to-peak measurement of fluorescence. Further, ex-vivo permeation of CXB-mu EG 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 mu EG and the enhancement in transdermal delivery over its conventional topical formulations.