The aim of this study was to analyze the distribution of chlorin type photosensitizers (PS): chlorin e6 (Ce6) and dimethyl ester of chlorin e₆ (DME), in human  adenocarcinoma HT29 monolayer and multicellular spheroid cell cultures. There is an assumption,  that the chemical modification of Ce6 molecules  causes a change  of intracellular location and the enhanced photosensitizing activity. Indeed, photodynamic therapy  on monolayer cell culture with DME showed two times higher photokilling ability comparing with that of non-modified analogue.

Ce6 and  DME biodistribution  processes  in tumor  tissue  were studied  on multicellular tumor  spheroids  model. Total amount  of DME in multicellular  tumor  spheroids  exceeded 1,3 times  accumulation  of Ce6. According  to  fluorescence  microscopy  studies, Ce6 and  DME distribution patterns in the spheroids bulk were similar. Application of 2D and 3D tumor models for the analysis of photosensitizer distribution may allow predicting the photosensitizer biodistribution  features for photodynamic therapy in vivo.

Optimized irradiation regimens for intraperitoneal photodynamic therapy with porphyrin and phthalocyanine photosensitizers are determined in in vitro and in vivo studies.

The experimental  study on НЕр2 cell line showed that reduce of power density for constant  light dose increased significantly the efficacy of photodynamic therapy (the reduce of power density from 20-80 mW/cm² to 10 mW/cm² had the same results (90% cell death) for half as much concentration of the photosensitizer).

The obtained results were confirmed in vivo in mice with grafted tumor S-37. For light dose of 90 J/cm²  and power density of 25 mW/cm² none of animals in the experimental  group had total resorption of the tumor. For the same light dose and decrease  of power density to 12 mW/cm²  total tumor resorption was achieved in 34% of animals, 66% of animals died from phototoxic  shock. For twofold decrease  of light dose – to 45 J/cm²  with the same low-intensity power density (12 mW/cm²) we managed total tumor resorption in 100% of animals.

In the following studies of optimized irradiation regimen for intrapleural photodynamic therapy the reaction of intact peritoneum of rats on photodynamic exposure was assessed and optimized parameters of laser irradiation, which did not cause necrosis and intense inflammatory reaction of peritoneum, were determined – light dose of 10 J/cm²  with power density of mW/cm².

Thus, the reasonability for use of low-intensity regimens of irradiation for intraperitoneal photodynamic therapy was confirmed experimentally with possibility of high efficacy of treatment without inflammatory reactions of peritoneum.

Results  of  autofluorescence dermatoscopy  using  videodermatoscope  «EcoSkin»  in  patients   with  different  dermatologic diseases  are represented. The study included 64 patients, 27 of them had different types of psoriasis, 11 – acne, 3 – rosacea, 5 – eczema, 3 – mite-induced dermatitis, 4 – superficial mycosis of the glabrous skin, 7 – atopic dermatitis, 4 – seborrheic dermatitis. The major changes of autofluorescence were detected in pathological foci in patients with psoriasis. Authors suppose that increased autofluorescence of porphyrins in psoriatic plaques in the study is associated  with enhanced prolyferation in pathological  tissues and with liver dysfunction. The analysis of autofluorescence images in patients  with rosacea, eczema, atopic and mite-induced dermatitis did not show significant difference in autofluorescence images of affected skin comparing  with intact skin in same patients. In patients  with acne a pattern of spot red-orange autofluorescence of skin in seborrheic  areas corresponding with location of openings  of pilosebaceous apparatus was detected that  was associated  by authors  with Propionibacterium acnes infection.

The article summarizes the main mechanisms  underlying the radiosensitizing effect of photosensitizers.

According to literature data many authors  consider the formation of reactive oxygen species to be the key element  in the implementation of the antitumor  effect of ionizing radiation, which transfers the photosensitizer molecule from the ground  state to the excited state. Their formation leads to the development of oxidative stress. The consequence of the realization of the oxidative stress induced by ionizing radiation is apoptosis of tumor cells.

The first photosensitizers, which radiosensitizing  activity was confirmed, were hematoprofyrin and photophryn II. A detailed  analysis of the results of experimental  studies of radiosensitizing effect of photosensitizers on cell culture and laboratory animals with transplanted lines of malignant gliomas (glioma C6, gliosarcoma 9L, glioblastoma U87-MG) was made.

The method of tumor radiosensitizing by administration of photosensitizers has been tested in patients with recurrent gliomas grade III-IV in a number of oncological centers. The obtained results show its good tolerability and antitumor  efficacy.

We have not found publications  on the study of the radiosensitizing effect of chlorine-based photosensitizers in the available literature, that makes following studies in this field relevant.

The article presents  a clinical observation  of the patient  of 38 y.o. with cancer of the left breast stage IIIC урТ4bN3М0L1V1. On the 1^st  step of the treatment the patient  had 2 courses of CAF neoadjuvant chemotherapy, on the 2^nd  step – extended radical mastectomy on the left with intraoperative photodynamic therapy and closure of the defect with ТRАМ-flap, on the 3^rd step – continuation of the chemotherapy (8 courses), on the 4^th  step  – radiation  therapy  to the chest wall on the left and zones of regional lymph drainage, targeted therapy  with herceptin  a (1 year). Four years later a silicone implant was inserted  into the left breast. Corrective surgery (reduction  mammoplasty on the right side) was performed in april, 2017. Currently, the patient has remission of the disease of the left breast, the period of remission accounts for 8 years. 

The  results  of the  clinical observation  of a female  patient  with squamous cell carcinoma  of the  cheek  skin treated  by the  method of photodynamic therapy (PDT) using the photosensitizer of fotoditazin are represented. The patient  had single course of PDT. Fotoditazin was injected in a dose of 0.8 mg/kg of body weight as a single intravenous  infusion in 0.9% sodium chloride. The irradiation was performed  once, 2.5 h after injection of the photosensitizer (power density of laser irradiation – 200-300 mW/cm², light dose of a single session of 300-350 J/ cm²). There were no side effects after photosensitizer injection and after irradiation. The result of the treatment was defined as partial tumor regression. For nowadays the follow-up period is 2 months. The repeated course of PDT is scheduled.