Direct imaging of singlet oxygen luminescence generated in blood vessels during photodynamic therapy

Singlet oxygen (O-1(2)) is commonly recognized to be a major phototoxic component for inducing the biological damage during photodynamic therapy (PDT). In this study, a novel configuration of a thermoelectrically-cooled near-infrared sensitive InGaAs camera was developed for imaging of photodynamically-generated O-1(2) luminescence. The validation of O-1(2) luminescence images for solution samples was performed with the model photosensitizer Rose Bengal (RB). Images of O-1(2) luminescence generated in blood vessels in vivo in a well-controlled dorsal skinfold window chamber model were also recorded during PDT. This study demonstrated the capacity of the newly-developed imaging system for imaging of O-1(2) luminescence, and the first reported images of O-1(2) luminescence in blood vessels in vivo. This system has potential for elucidating the mechanisms of vascular targeted PDT.