Cationic polymer-based micro-emulgel with self-preserving ability for transdermal delivery of diclofenac sodium

The objective of the present study was to develop a topical preparation with enhanced skin permeation, high safety and self-preserving ability. Microemulsion (ME) and cationic polymer based micro-emulgel (CPBM) were investigated for the transdermal delivery of diclofenac sodium (DS). Medium-chain triglyceride was selected as the oil phase of ME due to its good solubilization of DS and high safety. Orthogonal test was applied to optimize the formula of ME based on the cumulative skin permeation amount in vitro after preliminary formula test. Chitosan (CS) or polylysine was employed as the cationic polymer in the formula of CPBM. The transdermal delivery of DS was evaluated through in vitro skin permeation test. The results showed that the skin permeation rate of DS from the optimized CPBM (126.17 ± 15.82 μg/cm 2 /h) were 1.86-folds and 5.76-folds higher than that of DS commercial Emulgel and DS control hydrogel, respectively. MEs and the cationic polymer were found to have skin penetration co-enhancing effect when they were combined in the CPBM system. Furthermore, the CPBM showed a good growth inhibition of E. coli and S. aureus. The stability test revealed that the CPBM was stable at room temperature and 4 °C for a period of three months.