Emulgels Containing Carbopol 934P and Different Vegetable Oils for Topical Propolis Delivery: Bioadhesion, Drug Release Profile, and Ex Vivo Skin Permeation Studies

Topical administration can enable a more efficient therapy based on the improved bioavailability and patient compliance. Wounds and infections can lead to modifications of skin physiology and body protective function. Propolis (PRP) is utilized for skin protection and treatment. However, PRP extracts do not show suitable rheological characteristics and can cause irritation, pain, ulceration, and healing difficulties when they are administered on the harmed skin. Emulgels composed of Carbopol 934P (C934P) and different vegetable oils have been proposed for propolis extract release and may be a good strategy for topical delivery. The aim of this study was to investigate the bioadhesive properties, PRP release profile, skin permeation, and retention, by Franz’s diffusion cell and photoacoustic spectroscopy (PS), of these emulgels. Formulations were composed of C934P and passion fruit oil (PF), sweet almond oil (SA), or andiroba oil (AO). PRP or by-product extracts were added to the systems, drug release profile was investigated, and porcine ear skin was utilized for analyses of bioadhesive properties, skin permeation, and retention. All formulations displayed similar bioadhesive force (0.05–0.07 N); PRP release was modified (prolonged), dependent on formulation composition, and mainly governed by diffusion. PS and analysis using diffusion cell showed that the systems could provide dermal permeation and retention, which was more effective for formulations containing AO. Considering the importance of propolis for many skin therapies, the emulgels containing AO for PRP delivery are worthy of biological studies and further clinical evaluation.