In this paper we studied the photodynamic activity (the rate of molecular oxygen utilization during irradiation) of methylene blue (MB) in erythrocyte suspensions in vitro. Using spectroscopy and confocal microscopy with fluorescent sensors for singlet oxygen and other active oxygen species, it was shown that with an increase in the MB concentration (10–100 mg/kg), the molar photodynamic activity decreases. It was found that 5–10% of the MB added to erythrocytes tightly binds to the erythrocyte membranes, and the generation of singlet oxygen (¹O₂) is suppressed in favor of type I reactions (formation of H₂O₂, O₂•⁻, •OH). Another 40% of the MB added to erythrocytes is converted into a colorless leuco form, but is reoxidized back to MB under photodynamic exposure. The maximum relative quantum yield of ¹O₂ generation (φ_Δ ) among those measured in erythrocyte suspensions was 0.014 for a 10 mg/kg MB concentration, which is an order of magnitude lower than the values for MB in organic solvents and for the aluminum sulfonated phthalocyanine comparison photosensitizer (PS) (φ_Δ = 0.38). Interaction with erythrocytes (aggregation, reduction to the leuco form, competition for oxygen) explains the decrease in the MB efficiency under physiological conditions compared to organic solvents. The obtained results are important from the point of view of optimizing the systemic use of MB in photodynamic therapy.

The use of UV-C radiation for the treatment of tumors is a stand-alone therapeutic intervention that can induce cellular apoptosis and is independent of photosensitizer or oxygen concentration in tumor. To explore the potential of using X-ray excited UV-C luminescent nanoparticles as a basis for creating drugs to improve radiation therapy, two colloidal solutions of monoclinic La_1–x Pr_x PO₄ nanoparticles with different morphologies of large nanofibers (x = 0.02) or small nanorods (x = 0.05) were prepared using a microwave-assisted hydrothermal method. Comparison of X-ray excited UV-C luminescence of colloidal solutions showed approximately 6.3 times higher brightness for larger nanoparticles. The intrinsic and X-ray-induced cytotoxicity of the prepared colloidal solutions on the viability of cancerous Mh22a and healthy L929 cell cultures were studied using MTT assay and fluorescence microscopy. Fluorescence microscopy showed differences in the types of cell death (apoptosis or necrosis) after incubation with nanofiber or nanorod samples. X-ray irradiation was performed in two modes with different voltage on the X-ray tube (50 and 80 kV) and the same radiation dose (8 Gy). Groups of cells incubated with nanoparticles and irradiated with 50 kV mode showed greater death rate. According to MTT analysis, irradiation of cells incubated with La_0.98 Pr_0.02 PO₄ nanofibers at a concentration of 2 mg/mL reduced survival by 20-30%, and at the same time, according to fluorescence microscopy data, the number of cells undergoing apoptosis exceeded the number of cells that died through necrosis and reached 50-70%. Quantitative analysis of the relative number of dead cells caused by X-ray-induced cytotoxicity of La_0.95 Pr_0.05 PO₄ nanorods did not reveal statistically significant results in reducing cell viability.

Polycationic photosensitizers have previously demonstrated high in vitro efficacy against lung cancer cells, including cancer stem cells, and low dark cytotoxicity. Polycationic phthalocyanines have high quantum yield of singlet oxygen and photostability. In addition, it is possible to relatively simply introduce different metal-complexing agents and substituents into phthalocyanine macrocycles, which enables varying their photophysical characteristics. In this work, we studied photophysical properties of photosensitizers based on polycationic phthalocyanine derivatives with different chemical structure with strong absorption in the long wavelength region (680–690 nm). The studied photosensitizers exhibit negligible aggregation in the 1–100 μM concentration range and show very high phototoxicity in an in vitro study on A549 lung carcinoma cells (IC₅₀ of 60–100 nM for ZnPcChol₈ and 100–300 nM for 4αZnPc4⁺ and 4αβZnPc4⁺, depending on the light dose), and low dark cytotoxicity.

Intraoperative determination of optical properties of biological tissues is an important task of medical physics, in particular, for photodynamic therapy, because it allows personalizing photodynamic treatment by accurately calculating the required light dose. In this work, we propose a new approach to simultaneous measurement of diffuse reflectance and transmission spectra of the colon wall tissue during intestinal anastomosis, based on the use of two fiber-optic devices to deliver broadband radiation both from the side of the intestinal lumen and from the outer side of the intestinal wall, from which diffuse scattered light is also recorded. To restore the optical properties of these tissues it was proposed to use the Kubelka-Munk model with transformation of the optical parameters of the model into the optical parameters of the diffusion approximation theory with custom equations based on the results of numerical modeling. The proposed approach have been tested ex vivo on the biological samples of GIT tissues, allowing us to conclude on its applicability in clinical conditions.

The article presents a clinical case of successful elimination of mechanical jaundice by means of a course of photodynamic therapy in a patient with a malignant neoplasm of the major duodenal papilla and multimorbid concomitant pathology. The patient, admitted with a clinical picture of mechanical jaundice, after additional examination was given a final diagnosis - moderately differentiated adenocarcinoma of the major duodenal papilla, stage IIa (T2N0M0), complicated by moderate mechanical jaundice. After primary stenting, a series of three consecutive courses of combined systemic and local photodynamic therapy were performed with a three-month interval between them. During the last course, stent migration into the duodenum was detected. Nevertheless, the complex therapy allowed to effectively eliminate the manifestations of mechanical jaundice, stabilize the patient's condition, prevent further growth of the primary tumor, restore the patency of the ducts of the major duodenal papilla and avoid relapses of mechanical jaundice, despite the migration of the stent. This experience demonstrates the promise of the photodynamic approach for solving complex clinical situations associated with tumor damage to the biliary system and allows to consider this method as an alternative in situations of high risk of complications of traditional surgery.

The aim of the study was to collect and analyze published data from clinical trials on the efficacy of photodynamic therapy (PDT) using 5-ALA-based drugs and its esters in patients with basal cell carcinoma (BCC). The review was conducted using the PubMed and ClinicalTrials.gov databases for the period from 1995 to 2025. Large prospective and retrospective studies with more than 20 patients were included in the analysis. The efficacy of PDT was examined and compared with traditional treatment methods. The analysis demonstrated significant efficacy of PDT in the treatment of BCC. The complete regression rate ranged from 84% to 99% after 3 months of therapy, from 62% to 96% after 12 months, and from 70% to 91% after 5 years. A significantly better cosmetic outcome was recorded compared with surgical methods. Studies have confirmed that PDT has a high safety profile, with severe side effects rare. The most common adverse effects include mild skin irritation, redness, and mild discomfort, which resolve on their own.