Carbopol hydrogel/sorbitan monostearate-almond oil based organogel biphasic formulations: Preparation and characterization of the bigels

Purpose: To obtain and evaluate carbopol hydrogel/sorbitan monostearate-almond oil-based organogel biphasic formulations (bigels) as a semi-solid vehicle for medicated topical applications. Methods: Bigel formulations were obtained under mild conditions at a hydrogel/organogel ratio of 80/20, 70/30, and 60/40 (w/w). Their stability, viscosity, spreadability, microarchitecture, and acute skin toxicity were evaluated. Results: Two formulations, prepared at ratios of 80/20 and 70/30, were stable based on intermediate stability testing, and had a similar viscosity and spreadability (38.0 +/- 1.0 mm and 37.3 +/- 0.6 mm, p > 0.05, respectively). Both of these formulations had a bimodal droplet size distribution and very similar values for the droplet mean diameter (0.33 +/- 0.05 mu m and 2.35 +/- 0.44; and 0.34 +/- 0.04 mu m and 2.59 +/- 0.21 mu m). The formulation obtained at a ratio of 60/40 was unstable during storage. The in vivo results did not reveal any signs of skin toxicity. Conclusion: Considering their beneficial properties, the developed bigels are a potential semi-solid vehicle for topical application and exhibit a moisturizing effect.