1. Institute of Chemistry, Neuchâtel University, avenue de Bellevaux, P.O. Box 2, CH-2007 Neuchâtel, Switzerland, University Institute of Pathology, Centre Hospitalier Universitaire Vaudois (CHUV) and University of Lausanne (UNIL), Bugnon 25, CH-1011 Lausanne, Switzerland, and Swiss Federal Institute of Technology (EPFL), Laboratory of Photomedicine, EPFL, CH-1015 Lausanne, Switzerland