Photomechanical delivery of 100-nm microspheres through the stratum corneum: Implications for transdermal drug delivery

Background and Objectives: Photomechanical waves (PWs) render the stratum corneum permeable and allow molecules to diffuse into the epidermis. The aim of this study was to investigate the probe size that could be delivered through the stratum corneum and into the epidermis. Study Design/Materials and Methods: A single PW was applied onto the rat skin in vivo. Aqueous suspensions of fluorescent microspheres, 100 nm in diameter, were used as probes for transdermal delivery. The presence of the microspheres in the epidermis was measured by a fiber-based spectrofluorimeter after the stratum corneum was removed by tape-stripping (TS). Results: Exposure of the rat skin to a PW permeabilized the stratum corneum and allowed the fluorescent microspheres to diffuse into the epidermis. Conclusions: The experiments show that PWs can facilitate the delivery of very large molecules and probes into the epidermis.