The research presents a novel synthetic photosensitizer for photodynamic therapy (PDT) of malignant tumors - meso-tetra(3-pyridyl) bacteriochlorin, which absorbs at 747 nm (in the long-wavelength region of the spectrum) and is stable when stored in the dark. H2Py4BC demonstrates pronounced photoinduced activity in vitro against tumor cells of various genesis (IC50 varies from 21 to 68 nM for НЕр2, EJ, S37, CТ26, and LLC cultured cells) and provides in vivo pronounced antitumor efficacy in the treatment of mice bearing small or large S37, Colo26, and LLC metastatic tumors, as well as in the treatment of rats bearing RS-1 liver cholangioma. As a result, total regress of primary tumor nodules and cure of 40 to 100% of the animals were proved by the experiment criteria, MRI, and histological analysis. Meso-tetra(3-pyridyl) bacteriochlorin quickly penetrates and accumulates in the tumor tissue and internal organs of mice, and after 24 hours 80% of the dye is excreted from skin as well as 87% - 92% from liver, kidneys, and spleen.

Background Research in the subject of the influence of SARS-CoV-2 mechanisms on human’s homeostasis remains actual problem. Particular interest is the study of pathomorphological changes in the appendix in children with COVID-19. Objectives Aim of the study: morphological and molecular biological evaluation of the appendix in children of different age groups with COVID-19. Methods Groups were formed on the basis of anamnestic, clinical and morphological data: I (n = 42; aged 2 to 18 years, average - 10.8 years) – with an established clinical diagnosis: coronavirus infection (COVID-19; PCR+); II (n = 55; aged 2 to 18 years, average - 9.7 years) – with a confirmed clinical diagnosis of acute appendicitis; collected before the onset of the COVID-19 pandemic in 2017-2019; III (n = 38; aged 2 to 18 years, average - 10.3 years) - control group. Histological and immunohistochemical studies were conducted using primary antibodies to CD3, CD4, CD68, CD163, CD20, CD138 and to pro-inflammatory (IL-1, IL-6) and anti-inflammatory (IL-4, IL-10) cytokines. Results In most samples of appendix in children with COVID-19 were discovered signs of destructive phlegmonous-ulcerative and gangrenous appendicitis. An increase in CD3+, CD4+, CD68+, CD163+, CD20+ CD138+ immunocompetent cells was found in the appendix of children with COVID-19. As well, there is an increase in pro-inflammatory (IL-1, IL-6) and anti-inflammatory (IL-4, IL-10) cytokines. Conclusions The aforementioned pathological and immunohistochemical changes were more pronounced in the group of children aged 6-12 years (childhood).