The Survival of the Infusoria Paramecium caudatum in the Presence of Aluminum Oxide Nanoparticles

Abstract: Acute toxicity of nanoparticles of aluminum oxide (Al2O3) with a size of 13–16 nm was investigated by the biotesting method using Paramecium caudatum ciliates in the concentration range of 10–100 μg/mL. Aluminum oxide has an acute toxic effect on paramecium at concentrations of 20–100 μg/mL. The mean lethal dose (LD50) is equal to the concentration of nanoparticles at which the mortality of ciliates in relation to the control reached 50%. The LD50 for Al2O3 nanoparticles is 23 μg/mL at a 24-h exposure. According to published data, the toxic effect of Al2O3 nanoparticles is specific and depends on the size and surface charge of the particles and on the interfacial interaction of nanoparticles with the cell surface, as well as on the concentration and exposure time

A historical-architectural analysis of the panoramic image of Kazan by Cornelis de Bruijn

© 2020 Saint Petersburg State University. All rights reserved. This essay presents the results of application of modern software for analysis of microscopic images in order to establish the veracity of an intriguing primary source, an early eighteenth-century depiction of the skyline of the city of Kazan. This image is an engraving made on the basis of a sketch of the city's panorama created by the Dutch artist and diarist Cornelis de Bruijn during his journey down the Volga in May 1703. The meticulous comparison between the computer processed drawing by de Bruijn and early photographs of Kazan enables to conclude that the Dutch traveler provided a highly accurate picture, the first of its kind, of the contours of Early Modern Kazan. In terms of precision, his picture surpassed earlier illustrations of the city such as those published by Adam Olearius. As a result, certain questions regarding the age of some of Kazan's landmarks, for example, the Söyembikä Tower, are clarified. It has been established that this building predates the eighteenth century, and the authors suggest that its purpose may have been different from being military or defensive. In addition, de Bruijn's illustration elucidates the nature of the renovation carried out in the defensive towers of Kazan's city walls during Peter the Great's reign when the risk of raids or invasions into Muscovite territory from the south and east diminished considerably, which reduced the importance of Kazan as a fortified stronghold

Fluorescent gold nanoclusters stabilized on halloysite nanotubes: in vitro study on cytotoxicity

Fluorescent gold nanoclusters (AuNCs) with an average diameter of 2.7 ± 1.0 nm stabilized with 11-mercaptoundecanoic acid were supported on halloysite nanotubes modified with aminosilane. The cytotoxicity of the obtained fluorescent material was investigated in A549 human cells. The AuNCs stabilized on halloysite showed good uptake by the cells. The material did not cause a pronounced toxic effect and visible membrane damage within the 25–50 μg/mL concentration range. An increase in nanocomposite concentration to 100 μg/mL led to massive cell death via apoptosis. This concentration-dependent toxicity mechanism allows for using AuNCs stabilized on halloysite for halloysite visualization in biological objects, bioimaging, and cancer therapy

Comparative characteristics of various fibrous materials in in vitro experiments

Aim. Comparative assessment of the effect of fibrous materials on cell cultures RAW264.7 and BEAS-2B. Methods. The effects of various fibrous materials - single-walled carbon nanotubes of two types (SWCNT-1 and SWCNT-2), differing in morphological characteristics, and chrysotile asbestos as a positive control - was assessed on two cell lines macrophages RAW 264.7 and human bronchial epithelium BEAS-2B cells. The studied materials' concentration range for experiments on cells was selected taking into account the SWCNT content in the air of the working area and the subsequent modeling of SWCNT deposition in the human respiratory tract. Suspensions of the studied materials were prepared based on cell culture media by ultrasonication. Cytotoxicity assessment after 48 hours of incubation was performed by using the MTS colorimetric assay. The expression level of apoptosis markers was assessed by immunoblotting using the corresponding monoclonal antibodies. Visualization of SWCNT-1, SWCNT-2 and chrysotile asbestos in BEAS-2B cell cultures was carried out by improved dark-field microscopy. Results. According to dark-field microscopy, all the studied fibrous materials were found on the surface or cytoplasm of the cells. SWCNT and chrysotile asbestos did not have a direct cytotoxic effect in the MTS assay and did not induce apoptosis according to the results of Western blotting in cell cultures of RAW264.7 macrophages and BEAS-2B bronchial epithelium. In the cells of the bronchial epithelium (BEAS-2B) that showed greater sensitivity, a slight increase in the expression of pro-apoptotic protein PARP, which was more pronounced for shorter SWCNT-2, was revealed. Conclusion. Both types of SWCNTs, despite the differences in morphological characteristics, demonstrated similar effects in in vitro experiments; this result, with its further verification, can have an important practical application in justifying approaches to determining the safety criteria for single-walled carbon nanotubes as a class of nanomaterials of the same type

Dispersion of Single-Walled Carbon Nanotubes in Biocompatible Environments

© 2020, Pleiades Publishing, Ltd. Abstract: The unique physical and chemical properties of carbon nanotubes (CNTs), including SWCNTs (single-walled carbon nanotubes), allow their applications in many fields, including biomedicine. The optical properties of SWCNTs are attractive for application in the field of nanobiotechnology compared to MWCNTs (multi-walled carbon nanotubes). An important objective of SWCNT application for biomedical purposes is obtaining homogenous dispersions characterized by bioavailability and biocompatibility. The possibility of obtaining homogenous dispersions of different types of SWCNTs in biocompatible media for further use in different biomedical experiments and applications has been investigated. The sizes of SWCNT agglomerates in prepared dispersions were measured by the method of dynamic light scattering; bioavailability was studied by dark field microscopy in BEAS-2B bronchial epithelium cells. The dispersions were analyzed for the presence of bacterial contamination. Biocompatible and bioavailable dispersions have been obtained on the basis of cell culture media and 1% bovine serum albumin, which can be used in experiments on assessing the safety of SWCNTs at biological objects but have a number of limitations in the field of biomedicine. Dispergents based on lung surfactant components, which could be used in biomedical applications (DPPC and Survanta®), did not show efficency

Ru/CdS Quantum Dots Templated on Clay Nanotubes as Visible-Light-Active Photocatalysts: Optimization of S/Cd Ratio and Ru Content

© 2020 Wiley-VCH GmbH A nanoarchitectural approach based on in situ formation of quantum dots (QDs) within/outside clay nanotubes was developed. Efficient and stable photocatalysts active under visible light were achieved with ruthenium-doped cadmium sulfide QDs templated on the surface of azine-modified halloysite nanotubes. The catalytic activity was tested in the hydrogen evolution reaction in aqueous electrolyte solutions under visible light. Ru doping enhanced the photocatalytic activity of CdS QDs thanks to better light absorption and electron–hole pair separation due to formation of a metal/semiconductor heterojunction. The S/Cd ratio was the major factor for the formation of stable nanoparticles on the surface of the azine-modified clay. A quantum yield of 9.3 % was reached by using Ru/CdS/halloysite containing 5.2 wt % of Cd doped with 0.1 wt % of Ru and an S/Cd ratio of unity. In vivo and in vitro studies on the CdS/halloysite hybrid demonstrated the absence of toxic effects in eukaryotic cells and nematodes in short-term tests, and thus they are promising photosensitive materials for multiple applications

Bidirectional alterations in antibiotics susceptibility in Staphylococcus aureus—Pseudomonas aeruginosa dual-species biofilm

© 2020, The Author(s). In mixed infections, the bacterial susceptibility differs significantly compared to monocultures of bacteria, and generally the concentrations of antibiotics required for the treatment increases drastically. For S. aureus and P. aeruginosa dual species biofilms, it has been numerously reported that P. aeruginosa decreases S. aureus susceptibility to a broad range of antibiotics, including beta-lactams, glycopeptides, aminoglycosides, macrolides, while sensitizes to quinolones via secretion of various metabolites. Here we show that S. aureus also modulates the susceptibility of P. aeruginosa to antibiotics in mixed cultures. Thus, S. aureus—P. aeruginosa consortium was characterized by tenfold increase in susceptibility to ciprofloxacin and aminoglycosides compared to monocultures. The same effect could be also achieved by the addition of cell-free culture of S. aureus to P. aeruginosa biofilm. Moreover, similar increase in antibiotics efficacy could be observed following addition of S. aureus suspension to the P. aeruginosa mature biofilm, compared to P. aeruginosa monoculture, and vice versa. These findings open promising perspectives to increase the antimicrobial treatment efficacy of the wounds infected with nosocomial pathogens by the transplantation of the skin residential microflora