Effect of the vehicle on in vitro skin permeation of glycolic acid loaded liposheres

Purpose: To evaluate the effect of the microencapsulation in lipospheres on glycolic acid percutaneous absorption from different vehicles. Methods: Lipospheres loaded with glycolic acid, prepared by the melt method using tristearin as the lipid phase and hydrogenated soybean phosphatidylcholine as the emulsifier, were introduced in three different cosmetic formulations (petrolatum jelly, W/O and O/W emulsions) obtaining a 10% glycolic acid concentration. The study of percutaneous absorption was carried out by means a properly adapted diffusion chamber through a lipophilized membrane simulating the horney layer. The data were compared with those obtained by assaying the formulations containing the unencapsulated active substance. Results: The entrapment of glycolic acid in lipospheres (loading level 27.2  4.1 % w/w) produced a significant decrease in glycolic acid skin penetration rate. Unlike the unencapsulated substance, showing a clear dependence on vehicle properties, the in vitro skin penetration behaviour from lipospheres resulted uneffected by the formulation. Conclusions: Lipospheres loaded with glycolic acid, characterized previously both in vitro for morphology, size, loading level and release and in vivo for skin tolerance and cell renewal efficacy, showed the capability to retain glycolic acid regardless its partitioning between the vehicle and the lipophilized membrane. Therefore, the microparticle structure, having a predominant role on the vehicle, can determine the modulation of the cutaneous absorption and, consequently, decrease glycolic acid side local effects.