Influence Of Absorption And Scattering Coefficients On Singlet Oxygen Luminescence During Pnotosensitization In Skin-stimulating Phantom

Singlet oxygen (1O2) is widely considered to be the major cytotoxic species generated during Type-II photochemical reaction of photodynamic therapy(PDT), and its production is crucial for the treatment outcome of PDT. The influence of absorption and scattering coefficients on singlet oxygen luminescence during photosensitization in the skin-stimulating phantom was quantitatively studied. For this, aluminum phthalocyanine disulfonic acid (AlPcS) was utilized as the model photosensitizer, and India ink and 20% Intralipid were chosen as the absorber and scatterer for optical phantom, respectively. An custom-built time and spectral-resolved near-infrared (NIR) detection system was used for singlet oxygen luminescence measurement in which the spectral signal discrimination can be achieved using three narrow-band filters centered at 1230,1270 and 1310nm. As compared to AlPcS diluted in pure PBS solution, the intensity of singlet oxygen luminescence, and the lifetimes of AlPcS triplet state and singlet oxygen were varied significantly as the increase of absorption and scattering coefficients for skin-stimulating phantom. The obtained results indicate that the real singlet oxygen luminescence could be only determined by subtract NIR background signal from the control sample, while subtraction using NIR background signal obtained from the reference filters 1230 and 1310 nm is not reliable for skin-stimulating phantom. This study implies that NIR background signal from control sample in vitro or lesion in vivo is required to quantify singlet oxygen production during photosensitization.