Investigation of the Changes in Extinction Spectrum of Modern Chlorine-Containing Photosensitizing Drugs under the Visible Light Action

The paper presents the results of a study of the extinction spectra (350–900 nm) of aqueous solutions of modern chlorine-containing photosensitizing drugs for photodynamic therapy “Chloderm" (Chloderm, Russia) and "Chloderm with hyaluronic acid" (Chloderm, Russia) before and after irradiation by visible light with wavelengths of 405 nm, 450 nm, and 656±10 nm, with exposure time 0–20 min and intensity 0–200 mW/cm2. It is demonstrated that the addition of hyaluronic acid does not deform the shape of the extinction spectrum of the photosensitizing drug but reduces its absorption in proportion to the drop in the concentration of the photosensitizer in the drug. Photodynamic light action in the investigated range of parameters leads to a slight decrease in the extinction coefficient of both drugs at the wavelengths of the exposure, but significantly reduces extinction and deforms the Qy 00 absorption band (600–700 nm), thereby changing the ratio of monomers and tetramers in the drugs. This band is most significantly deformed after exposure to light with a wavelength of 656±10 nm, the least – with a wavelength of 450 nm.