Applications of Photoacoustic Spectroscopy to Problems in Dermatology Research

The technique of photoacoustic spectroscopy (PAS) was applied in two areas of dermatology research: 1) drug detection and drug diffusion rates in skin, and 2) thermal properties and water content of skin. The drug studies involved detection of the drug tetracycline in the skin and determination of the diffusion rate of the drug through the skin. The water content studies involved determining the thermal properties of the epidermis as a function of water content and the effect of the water concentration gradient across the epidermis. A multilayer model for the photoacoustic effect was developed to account for the nonuniform thermal properties of the intact skin arising from the water concentration gradient. This model was used to determine the width of the region comprising the diffusional barrier in skin. The width of the barrier region was found to correspond to that of the outermost layer of the epidermis, the stratum corneum. This finding coincides with previous research indicating that the stratum corneum comprises the primary barrier to the diffusion of water through the epidermis.