This is the first study showing that singlet oxygen kinetics of topically applied photosensitizers coincides with the microarchitecture of skin, e.g., fissures and hair follicles. The kinetics indicate a chemical interaction of singlet oxygen with the skin, which allows differentiating between residual crème, e.g., in the follicular orifice, and photosensitizer penetrated into the skin. We show the feasibility of an easy-to-use fiber optic application providing the opportunity for in situ investigation, as well as a setup with focused optics for high-resolution two-dimensional scanning of singlet oxygen luminescence kinetics in skin samples. The results show that time-resolved singlet oxygen luminescence detection in tissue is a desirable tool for medical therapy, diagnostics, and evaluation of singlet oxygen interaction with biological environments.

LEDs have more and more influence on daily life as well as on scientific equipment. In this paper we want to report results gained with the first LED powered setup for time resolved detection of the singlet oxygen luminescence in solution as well as in cell suspension. The results show, that this setup can compete with the best laser powered setups worldwide. The high sensitivity comes along with a superior long term stability and wavelength versatility. Setups based on LED excitation can simplify the technical part of such measurement very much and reduce the costs, making this technology available for a wider scientific community.