Investigation of changes in the absorption spectrum of modern chlorine-containing medicines for photodynamic therapy and methylene blue as a result of exposure to led emissions with a wavelength of 656 $\pm$ 10 nm

Changes in the absorption spectra of aqueous solutions of modern chlorinated photosensitizing drugs for photodynamic therapy “Revixan” (Areal, Russia) and “Chloderm” (Chloderm, Russia) in the range of 600–700 nm depending on the intensity and time of exposure to LED emission with a wavelength of 656 $\pm$ 10 nm have been studied. The parameters of the CIE Lab color model of the “Revixan” water solution image before and after LED exposure have been studied. In the range of 400–900 nm, the changes in the absorption spectra of an aqueous solution of methylene blue with different initial concentrations after exposure to LED emission with a wavelength of 656 $\pm$ 10 nm and an intensity of 180 $\pm$ 20 mW/cm$^2$ have been studied. It has been shown that the effect of LED emission changes the absorption spectra of the studied substances and increases the parameter $L$ (brightness) of the CIE Lab color model for “Revixan”. An increase in the intensity of the LED emission and exposure time causes a decrease in the absorption for “Revixan” and “Chloderm” in the range of 600–700 nm and a shift of the peak of the absorption band lying in this range to the infrared region. The effect of the LED emission on an methylene blue aqueous solution causes a decrease in its absorption in the range of 400–900 nm.