Topical delivery and photodynamic evaluation of a multivesicular liposomal Rose Bengal

We investigated the pharmaceutical and physicochemical properties of different multivesicular liposome (MVL) formulations for the delivery of Rose Bengal (RB) into skin layers for topical photodynamic therapy. The drug content, uniformity, spreadability and release kinetics of the optimum hydrogel formulation were studied. Skin penetration of the prepared gels was studied in albino mice using fluorescence microscopy and the photodynamic properties were evaluated. The loading efficiency of MVL ranged from 56% to 79%. In vitro RB release from MVL followed Higuchi's diffusion mechanism and the amount of RB released after 2 h from the optimum MVL (comprising d,l-dipalmitoylphosphatidyl choline, cholesterol and tripalmitin at a molar ratio of 1:0.7:0.1, respectively) was 2.5-fold higher than from the other MVL formulations. The type and concentration of phospholipids did not significantly (p > 0.05) affect vesicle size but significantly (p < 0.05) increased the encapsulation capacity and thermal properties. RB in hydrogel was spreadable and uniformly distributed. Fluorescence microscopy 30 min after topical application to the skin of mice showed that RB loaded into MVL was significantly (p < 0.05) more distributed into the dermal layers than free RB which accumulated in the epidermis. This finding was confirmed by the presence of superficial necrotic cells in histological sections of skin treated with free RB and the presence of RB in the deep dermal layers of sections of skin treated with the MVL-RB formulation and irradiated for 10 min with light of wavelength 550 nm from a light emitting diode at 80 mW. MVL hydrogel is a promising topical delivery system which allows successful delivery of RB into skin layers for different photodynamic therapies in dermatology.