Optimization effect of light on endogenous porphyrins in soft biological tissues

Light action spectra for skin chromophores are simulated. Endogenic porphyrins (Pp IX, Cp III, and Up III) are selected as target chromophores. They can produce singlet oxygen (SO) under tissue irradiation, which acts as a natural photosensitizer. The SO is toxic for cancer cells. This process is known to be widely used in photodynamic therapy (PDT). The irradiation at wavelengths ranging from $610$ to $630$ nm is significantly stimulates the production of endogenous porphyrins SO over the entire thickness of the dermis ($2$–$3$ times dermis at a depth $z < 0.15$ mm; $10$–$12$ times dermis $z\geqslant 0.15$ mm) compared with exposure to absolute absorption maxima (at about $501$ nm for uroporphyrin (UpIII), $495$ nm for coproporphyrin (CpIII) and $505$ nm for protoporphyrin (PpIX)). The presented results can provide new opportunities for the selection of the irradiation wavelengths under application of traditional PDT methods.