Photochemical effects and hypericin photosensitized processes in collagen

Emission and excitation spectra of collagen were recorded in the ultraviole t and visible regions. The existence of several types of chromophores absor bing and emitting throughout these spectral regions was observed. It was sh own that laser irradiation at 355 and 532 nm caused collagen fluorescence p hotobleaching by 30%, when the delivered light doses were 9 and 18 J/cm(2), respectively. This process of collagen fluorophores photodestruction was f ound to be a one-photon effect. The effect of hypericin (HYP), a polycyclic quinone, photosensitization on collagen was also studied. Addition of HYP aqueous solution to collagen produced quenching, redshift of the maximum, a nd broadening of the spectral form of its fluorescence. These effects becam e more prominent with increasing HYP concentration. The fluorescence of HYP sensitized collagen decreased in a spectrally nonproportional manner durin g laser irradiation at both 355 and 532 nm. (C) 2001 Society of Photo-Optic al Instrumentation Engineers.