A non-invasive laser enhancing transdermal drug delivery technique has been investigated. The second harmonic wavelength of 532 nm of a Q-Switched Nd:YAG laser with pulse duration of 15 ns was used to irradiate on a black polyethylene sheet covering on the surface of the drug solution, and hence produced pressure waves in the solution. Porcine skin and Rhodamine B were used as skin model and reagent respectively. Fluorescence microscope was employed to examine the mechanisms of drug delivery via the skin samples after laser treatment. The experiment revealed that the penetration depth of Rhodamine B under the illumination of laser increased with the energy density of the laser beam. After 20 laser shots at laser energy density of 70 mJ/cm2, the penetration depth reached 440 μm in 30 minutes, which was about three times as that without laser illumination. One possible explanation was that laser-induced pressure waves formed microchannels in the stratum corneum of the skin tissue. These microchannels provided much more effective paths for infiltration of Rhodamine B through the SC than follicular and intercellular paths. The drug solution diffused into the SC under the concentration gradient through the channels.
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