25154 Enhanced topical delivery of salicylic acid from an encapsulated system

Abstract

Salicylic acid is a beta hydroxy acid that is clinically proven in the prevention and treatment of acne by encouraging skin exfoliation and unclogging of pores. Despite its bioactivity, the low water solubility of salicylic acid makes it challenging to formulate, and also limits its permeation into skin when applied topically. Various carrier-based delivery systems have been developed in recent years targeting either enhanced penetration for better efficacy, or controlled release for less side effect and long-lasting benefit. Among them, the multilamellar vesicle (MLV) delivery system encapsulates active ingredients in its onion-like structure; the individual “layers” peel off over time to provide deep and sustained active release. In this study, we compared the skin penetration of 2% salicylic acid from a topical gel with and without a specific MLV delivery system. Human skin explants were treated with the gel formulations for 24 hours in triplicates on a Franz diffusion cell setup. ATR-FTIR imaging was conducted on skin cross sections after the treatment. Unique spectrospopic signals (eg, 850 cm-1) were identified to monitor salicylic acid. The hyperspectral images revealed that a deeper and overall greater level (2-fold) of salicylic acid was delivered into skin through MLV encapsulation as compared with the control formula, which contains an equal amount of salicylic acid in free form. This proves that the MLV is an effective vehicle for topical delivery of salicylic acid.