Oil components modulate the skin delivery of 5-aminolevulinic acid and its ester prodrug from oil-in-water and water-in-oil nanoemulsions

Abstract

The study evaluated the potential of nanoemulsions for the topical delivery of 5-aminolevulinic acid (ALA) and Me ALA (mALA). The drugs were incorporated in oil-in-water (O/W) and water-in-oil (W/O) formulations obtained by using soybean oil or squalene as the oil phase. The droplet size, zeta potential, and environmental polarity of the nanocarriers were assessed as physicochem. properties. The O/W and W/O emulsions showed diams. of 216-256 and 18-125 nm, which, resp., were within the range of submicron- and nano-sized dispersions. In vitro diffusion expts. using Franz-type cells and porcine skin were performed. Nude mice were used, and skin fluorescence derived from protoporphyrin IX was documented by confocal laser scanning microscopy (CLSM). The loading of ALA or mALA into the emulsions resulted in slower release across cellulose membranes. The release rate and skin flux of topical drug application were adjusted by changing the type of nanocarrier, the soybean oil O/W systems showing the highest skin permeation. This formulation increased ALA flux via porcine skin to 180 nmol/cm2/h, which was 2.6-fold that of the aq. control. The CLSM results showed that soybean oil systems promoted mALA permeation to deeper layers of the skin from ∼100 μm to ∼140 μm, which would be beneficial for treating subepidermal and s.c. lesions. Drug permeation from W/O systems did not surpass that from the aq. soln. An in vivo dermal irritation test indicated that the emulsions were safe for topical administration of ALA and mALA. [on SciFinder(R)]