Partial ablation of stratum corneum by UV (193 nm) or IR (2.94 μm) pulsed lasers to enhance transdermal drug delivery rate

To develop the noninvasive transdermal drug delivery system, pulsed lasers (argon-fluoride excimer laser (ArF laser) and erbium:yittrium aluminum garnet laser (Er:YAG laser)) were used to partially ablate the stratum corneum (SC). Because of the barrier function of the SC to drug permeation, the number of drugs in particular macromolecules used in the transdermal drug delivery system without skin irritation has been limited. Ultrastructural changes on the SC surface of laser ablated Yucatan micropig skin in vitro were observed with environmental scanning electron microscope. This result indicated that the structural changes varied according to each laser sources and irradiation conditions (laser fluences and numbers of pulses). Many granular structures of about 2 μm were observed in the ablated sites on the ArF laser with lower fluence exposure (33 mJ/cm²/pulse, 215 pulses), and plane structures in the sites with higher fluence exposure (89 mJ/cm²/pulse, 80 pulses). In contrast, the ablation of the Er:YAG laser created some pores of about 20 μm across on the SC surface. Under the irradiation condition of the partial ablation, the skin permeability of macromolecule was enhanced. This partial SC ablation by the pulsed laser could be possible candidate of the noninvasive transdermal drug delivery system with good physiological conditions of skin.