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/cm 2 . 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.

The possibility of active laser delivery of a modern chlorine-containing photosensitizing drug Chloderm (Chloderm, Russia) under the nail plate by laser radiation with a wavelength of 450 nm for the purpose of photodynamic therapy of onychomycosis is studied. In an in vitro experiment, sequential laser microporation of the nail plate and active delivery of the drug under the nail plate by this laser radiation with an intensity of up to 200 W/cm2 were investigated. The results of studying the absorption spectra of an aqueous solution of Chloderm in the range of 400-900 nm before and after exposure to 450 nm laser radiation are presented. It is demonstrated that sequential laser microporation and active laser drug delivery under the nail plate is possible at laser radiation intensity greater than 178 W/cm2. It is shown that the maximum rate and efficiency of nail plate ablation by 450 nm laser radiation is achieved at an intensity of 200 W/cm2 and is 2750± 30 μm/s and 1.47 ± 0.05 μm/mJ, respectively. The delivery rate of Chloderm under the nail plate is 1.15± 0.1 mg/s. It is shown that exposure to 450 nm laser radiation at the intensity of 200 W/cm2 for a time sufficient to deliver the drug under the nail plate does not change the extinction coefficient of the drug at the laser wavelength and slightly changes the conformational state of Chloderm. Keywords: laser delivery, ablation, wavelength, absorption coefficient, chlorine-containing photosensitizing drug, laser radiation.

The possibility of active laser delivery of a modern chlorine-containing photosensitizing drug “Chloderm” (Chloderm, Russia) under the nail plate by laser radiation with a wavelength of 450 nm for the purpose of photodynamic therapy of onychomycosis is studied. In an in vitro experiment, sequential laser microporation of the nail plate and active delivery of the drug under the nail plate by this laser radiation with an intensity of up to 200 W/cm2 were investigated. The results of studying the absorption spectra of an aqueous solution of Chloderm in the range of 400–900 nm before and after exposure to 450 nm laser radiation are presented. It is demonstrated that sequential laser microporation and active laser drug delivery under the nail plate is possible at laser radiation intensity greater than 178 W/cm2. It is shown that the maximum rate and efficiency of nail plate ablation by 450 nm laser radiation is achieved at an intensity of 200 W/cm2 and is 2750 ± 30 μm/s and 1.47 ± 0.05 μm/mJ, respectively. The delivery rate of Chloderm under the nail plate is 1.15 ± 0.1 mg/s. It is shown that exposure to 450 nm laser radiation at the intensity of 200 W/cm2 for a time sufficient to deliver the drug under the nail plate does not change the extinction coefficient of the drug at the laser wavelength and slightly changes the conformational state of Chloderm.

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Double-stage active laser drug delivery (DSLADD) of an aqueous solution of methylene blue using Er:YLF laser radiation experimentally was investigated. Model for describe of the delivery of local drugs under a microporated nail plate taking into account the peculiarities of laser radiation exposure, capillary effects in microholes and diffusion in the nail plate was developed. The phenomenon of spreading of the drug consisting in the fact that after laser action drug is distributed in the nail bed not only in the area of the nail bed located directly under the microhole, but also along the border of the nail plate and the nail bed around the microhole was observed for the first time. Calculations performed within the framework of the developed model showed that, taking into account spreading phenomenon, the density of filling the nail area with microholes can be significantly reduced, which can proportionally increase the productivity of laser delivery in general.