Formulation and Evaluation of a Transfersomal Hydrogel of Salicylic Acid for the Treatment of Psoriasis
Abstract
Background: Psoriasis is a chronic inflammatory skin disease that severely impacts patients' quality of life. Traditional topical deliveries of salicylic acid (SA) often cause localized irritation and face systemic limitations due to the formidable barrier properties. Objective: This study aimed to formulate, optimize, and evaluate an ultra-deformable vesicular carrier system—transfersomes—incorporated into a carbopol hydrogel base for the sustained and enhanced topical delivery of salicylic acid. Methods: Salicylic acid-loaded transfersomes were prepared via the thin-film hydration technique utilizing Soya-phosphatidylcholine (PC) and Span 80 in varying ratios. The prepared vesicles were characterized for particle size, zeta potential, and entrapment efficiency (%EE). The optimized formulation (TF4) was successfully incorporated into three different concentrations of Carbopol 934 gel bases (0.5%, 1.0%, and 2.0% w/w). The hydrogels were extensively evaluated for their organoleptic parameters, pH, viscosity, spreadability, drug content, and in-vitro drug diffusion kinetics via a modified Franz diffusion cell over 14 hours. Results: The vesicle sizes of the prepared transfersomes ranged from 161.08 nm to 552.8 nm with an encapsulation efficiency between 63.70% and 90.89%. The optimized formulation, TF4, presented a vesicle size of 269.00 nm, high entrapment efficiency of 73.70%, and a stable zeta potential of -35.6 mV. The formulated hydrogels displayed excellent homogeneity and acceptable pH ranges (6.9 to 7.3). In-vitro diffusion profiling revealed that formulation TF2 (1.0% w/w Carbopol) exhibited the most balanced, controlled release profile, reaching 94.08% drug delivery at the end of 14 hours. Mathematical modeling demonstrated compliance with zero-order kinetics and a non-Fickian anomalous transport mechanism (0.5 < n < 1.0). Conclusion: The developed transfersomal hydrogel serves as an advanced, highly elastic vesicular platform that effectively bypasses the skin barrier, offering sustained release while potentially reducing the localized toxicity associated with standard salicylic acid treatments.