Percutaneous absorptiometry by a laser photoacoustic method and its applications (Accounts)

Skin plays not only a physical role as the shelter for the living body but also many important biological roles. Observing the out- or inside of skin by the photoacoustic (PA) method, new information that is difficult to measure can be detected. We have attempted to measure the percutaneous absorption of chemical substances in order to investigate the effect and the toxicity of medicinal compounds. To do this, we had to develop a PA cell that could detect a chemical substance on skin with high sensitivity and accuracy. Several such investigations have been reported; however the conventional open-ended PA cells had unfavorable signal to noise ratio (S/N) and sensitivity. We have reported the development of percutaneous absorptiometry using the laser PA method. A series of in vitro and in vivo percutaneous absorptiometries was performed. As a result, it was concluded that this PA method is applicable to percutaneous absorption in situ.