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The process of corrosion of composite welded joints of 20 steel and 08Kh18N9T stainless steel produced by manual argon-arc welding is investigated by electrochemical methods. It is shown that a contact galvanic couple is formed in the zone of the welded joint and, as a result, the surface of 20 steel in the vicinity of the weld turns into the anode and intensely corrodes. For this reason, composite welded joints should not be used in heart-power engineering. [ABSTRACT FROM AUTHOR]

The aim of this study was to create and evaluate a cell model designed for in vitro and in vivo testing of anti-human PD-L1 therapeutic and diagnostic agents' specificity., Materials and Methods: Genetically modified cells expressing human PD-L1 (strain CT26-PD-L1) were obtained by retroviral transduction of murine CT26 carcinoma cells. PD-L1 gene activity was assessed by real-time PCR, and PD-L1 expression on cells was identified by flow cytometry. Cells were tested using recombinant single-domain human anti-PD-L1 antibodies (nanoantibodies) conjugated with radioisotopes 68 Ga or 177 Lu. Immunoreactive fraction and cell internalization of the radioconjugates were evaluated in vitro. For in vivo experiments CT26-PD-L1 cells were transplanted into mice, radioimmunoconjugates were injected 9-14 days later, in 1-48 h the tumors were retrieved and subjected to direct radiometry. Intact CT26 cells not expressing the antigen served as a control., Results: CT26-PD-L1 strain of murine tumor cells expressing human membrane PD-L1 was created. When transplanted into intact BALB/c mice or sublethally irradiated F1(DBA×BALB/c) mice, these cells formed tumors. Thus, a significant advantage of the model was the possibility of in vivo testing of human PD-L1-affinity agents using animals under conventional vivarium conditions. When radioimmunoconjugates were administered to tumor bearing mice, radionuclides accumulated in tumors generated from the transplanted CT26-PD-L1 cells, but not CT26 cells. CT26-PD-L1 cells internalized anti-PD-L1 nanobodies in vitro. Due to a high density of target molecules, CT26-PD-L1 cells allowed both to confirm pharmaceuticals' specificity and to quantify the target-binding fraction of conjugates in a single test., Conclusion: The created cells are the first genetically engineered cells designed to evaluate affinity of anti-human PD-L1 therapeutic and diagnostic agents in Russia. Test results confirmed the model suitability for in vitro and in vivo testing of the specificity of pharmaceuticals targeting human PD-L1., Competing Interests: Conflicts of interest. There is no conflict of interest.

Quantification of the immunoreactive fraction (IRF) of radioactive isotope-labeled antibodies or their fragments is necessary to assess the specific activity of radiopharmaceuticals. Traditionally, cells expressing the target molecules on their surface are used to determine IRF, but such analysis is time-consuming and has difficulties with standardization. The aim of the study was to develop a fast and reliable method for quantitative determination of IRF by 68 Ga-labeled VHH antibodies to PD-L1 based on the use of magnetic particles coated with antigen molecules., Materials and Methods: Commercially available magnetic particles coated with protein A have been used in our study. The antigen conjugated with the Fc fragment (PD-L1-Fc) was immobilized on the particles. The IRF value of 68 Ga radionuclide-labeled nanobodies (VHH) against PD-L1 ( 68 Ga-VHH-PD-L1) was determined using magnetic particles coated with antigen molecules and cells expressing the antigen on their surface. When VHH antibodies were conjugated to 68 Ga radionuclide, protein molecules were modified using bifunctional chelating agents: tetraazacyclododecanetetraacetic acid (DOTA) or deferoxamine (DFO). The magnitude of IRF was defined as the ratio of radioactivity specifically bound to particles or cells to the total radioactivity added to the sample., Results: The specificity of the 68 Ga-VHH-PD-L1 radioimmunoconjugate binding to the antigen-coated magnetic particles has been proved. Some special aspects, which should be taken into consideration when using this method, have been established. The comparison of the IRF estimates using the antigen-expressing cells and magnetic particles has not revealed any significant differences in the results obtained in our study. Nevertheless, the presented method based on magnetic particles with immobilized antigen molecules requires only 15 min to determine the radioimmunoconjugate IRF, which is of fundamental importance for the routine assessment of the specificity of radiopharmaceuticals containing short-lived isotopes., Competing Interests: Conflicts of interest. The authors have no conflicts of interest to declare.