Clobetasol propionate loaded nanostructured lipid carrier gel: formulation strategy and in vitro performance evaluation

Clobetasol propionate (CP) is a potent Class I corticosteroid widely used to treat dermatological conditions; however, its poor aqueous solubility limits bioavailability. In this study, a nanostructured lipid carrier (NLC)-based gel was developed via the microemulsion method to improve the topical delivery of CP. The formulation was optimized using stearic acid (solid lipid), Captex 300 (liquid lipid), Tween 20 and Span 80 (surfactants), and propylene glycol (co-surfactant), based on solubility and thermodynamic stability assessments. Vitamin E acetate was incorporated as an antioxidant to inhibit lipid oxidation and enhance formulation stability. The optimized CP-NLC (F5) formulation had a particle size of 75.96 ± 4.87 nm, a zeta potential of −23.88 ± 4.10 mV, and a polydispersity index (PDI) of 0.27 ± 0.11. Encapsulation efficiency was 93.72 ± 0.26%, and drug loading reached 100.69 ± 0.62%. Transmission electron microscopy (TEM) confirmed spherical morphology. The gel (CP-NLC-F5-G) prepared with Carbopol 934 demonstrated a pH of 5.58 ± 0.68 and drug content uniformity of 99.03 ± 1.18%. In vitro release studies using Franz diffusion cells revealed sustained CP release compared to a commercial product. Stability studies indicated long-term encapsulation retention, attributed to the antioxidant effect of Vitamin E acetate. These findings suggest the potential of CP-NLC systems for effective, sustained corticosteroid delivery with enhanced dermal retention.