This study combines several fluorescence detection methods to distinguish structural features of the synovium and cartilage tissues and to visualize the localization of endogenous porphyrins in the sensitized tissues. Specimens of synovium and cartilage tissues obtained from rabbits with antigen-induced monoarthritis after intra-articular 5-aminolevulinic acid methyl ester injection and those from healthy rabbits were investigated ex vivo by means of fluorescence spectroscopy, fluorescence intensity, and lifetime microscopy. The presence of endogenous porphyrins was confirmed with the fluorescence spectra measured on sliced sensitized specimens. Application of the lifetime-gating method on fast fluorescence lifetime imaging microscopy images, allowed separate visualization of tissue structures possessing different average lifetimes. The presence of the structures has been validated by histopathological imaging based on conventional rapid hematoxylin–eosin staining of the specimens. The fluorescence lifetime of endogenous protoporphyrin IX has been assessed and employed for visualization of sensitized tissues.
Photo-bleaching of in-vivo skin autofluorescence intensity under continuous low power laser irradiation has been
studied. Temporal behavior of single-spot fluorescence and spectral fluorescent images have been studied at continuous
405 nm, 473 nm and 532 nm laser excitation and/or pre-irradiation, with power densities well below the laser-skin safety
limits. Skin autofluorescence photo-memory effects (laser signatures) have been observed and analyzed, as well.