Photomechanical transdermal delivery: The effect of laser confinement

Background and Objectives: Photomechanical waves can transiently permeabili ze the stratum corneum and facilitate the delivery of drugs into the epider mis and dermis. The present study was undertaken to assess the effect of pu lse characteristics to the penetration depth of macromolecules delivered in to the skin. Study Design/Materials and Methods: Photomechanical waves were generated by confined ablation with a Q-switched ruby laser. Fluorescence microscopy of frozen biopsies was used to assay the delivery of macromolecules through t he stratum corneum and determine the depth of penetration. Results: Photomechanical waves generated by confined ablation of the target have a longer rise time and duration than those generated by direct ablati on. Confined ablation required a lower radiant exposure (from similar to7 J /cm(2) to similar to5 J/cm(2)) for an increase in the depth of delivery (fr om similar to 50 mum to similar to 400 mum). Conclusions: Control of the characteristics of the photomechanical waves is important for transdermal delivery as they can affect the depth of drug pe netration into the dermis. Lasers Surg. Med. 28:344-347, 2001. (C) 2001 Wil ey-Liss, Inc.