Topical gel based nanoparticles for the controlled release of oleanolic acid: design and in vivo characterization of a cubic liquid crystalline anti-inflammatory drug

BACKGROUND: Oleanolic acid (OA) has multiple pharmaceutical applications including anti-inflammatory activity, but low permeability of the molecule limits its widespread use. METHODS: A cubic liquid crystalline nanoparticle (LCNP)-based gel was prepared as a potential topical delivery system for OA. The LCNP-based gel was optimized using rheological, drug release kinetic, and ex vivo permeation studies. RESULTS: The studies showed that the OA was trapped in the interior of the LCNP with a crystal form of Pn3m space. The optimized LCNP formulation performed well using in vitro release studies for up to 12 h (85.49 ± 0.21%). Ex vivo permeation studies showed that the LCNP-based gel formulation was superior to a standard gel formulation. The r(2) value from the Peppas equation indicated good linearity, but showed irregular (non-Fickian) diffusion, suggesting that drug release was controlled by multiple processes. CONCLUSIONS: In this study, OA-loaded LCNPs were prepared by the precursor method, resulting in a well-characterized OA-LCNP gel preparation. The gel was shown to be effective in a rodent carrageenan-induced hind paw inflammation model with sustained efficacy after a single application.