Coating of polylactide films by chitosan: Comparison of methods

Control over biomaterials surface characteristics through surface modification or deposition of coatings is one of the key aspects of tissue engineering. This work was aimed to evaluate an effectiveness of various methods of chitosan-coating formations onto polylactide films using a number of techniques, such as vacuum deposition by electron-beam sputtering, chemical entrapment method, and electrospray procedure. Differently coated films were studied in terms of surface morphology (scanning electron and atomic-force microscopy), chemical structure (FTIR and X-ray photoelectron spectroscopy), and hydrophilic/hydrophobic balance (goniometry). The effect of coating technique on homogeneity of chitosan distribution over the substrate surface was evaluated using genipin and fluorescein isothiocyanate labeling as well as FTIR-microscopy. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48287.     

Structural Rearrangement of Dps-DNA Complex Caused by Divalent Mg and Fe Cations

Two independent, complementary methods of structural analysis were used to elucidate the effect of divalent magnesium and iron cations on the structure of the protective Dps-DNA complex. Small-angle X-ray scattering (SAXS) and cryo-electron microscopy (cryo-EM) demonstrate that Mg²⁺ ions block the N-terminals of the Dps protein preventing its interaction with DNA. Non-interacting macromolecules of Dps and DNA remain in the solution in this case. The subsequent addition of the chelating agent (EDTA) leads to a complete restoration of the structure of the complex. Different effect was observed when Fe cations were added to the Dps-DNA complex; the presence of Fe²⁺ in solution leads to the total complex destruction and aggregation without possibility of the complex restoration with the chelating agent. Here, we discuss these different responses of the Dps-DNA complex on the presence of additional free metal cations, investigating the structure of the Dps protein with and without cations using SAXS and cryo-EM. Additionally, the single particle analysis of Dps with accumulated iron performed by cryo-EM shows localization of iron nanoparticles inside the Dps cavity next to the acidic (hydrophobic) pore, near three glutamate residues.     

Measuring temperature profiles in high-power optical fiber components

We demonstrate a new method for measuring changes in temperature distribution caused by coupling a high-power laser beam into an optical fiber and by splicing two fibers. The measurement technique is based on interrogating a fiber Bragg grating by using low-coherence spectral interferometry. A large temperature change is found owing to coupling of a high-power laser into a multimode fiber and to splicing of two multimode fibers. Measurement of the temperature profile rather than the average temperature along the grating allows study of the cause of fiber heating. The new measurement technique enables us to monitor in real time the temperature profile in a fiber without the affecting system operation, and it might be important for developing and improving the reliability of high-power fiber components.     

Hydrophilicity of Graphene in Water through Transparency to Polar and Dispersive Interactions

Establishing contact angles on graphene‐on‐water has been a long‐standing challenge as droplet deposition causes free‐floating graphene to rupture. The current work presents ice and hydrogels as substrates mimicking water while offering a stable support for graphene. The lowest water contact angles on graphene ever measured, namely on graphene‐on‐ice and graphene‐on‐hydrogel, are recorded. The contact angle measurements of liquids with a range of polarities allow the transparency of graphene toward polar and dispersive interactions to be quantified demonstrating that graphene in water is hydrophilic. These findings are anticipated to shed light on the inconsistencies reported so far on the wetting properties of graphene, and most particularly on their implications toward rationalizing how molecules interact with graphene in water.     

Low temperature solution-phase growth of ZnSe and ZnSe/CdSe core/shell nanowires

High quality ZnSe nanowires (NWs) and complementary ZnSe/CdSe core/shell species have been synthesized using a recently developed solution-liquid-solid (SLS) growth technique. In particular, bismuth salts as opposed to pre-synthesized Bi or Au/Bi nanoparticles have been used to grow NWs at low temperatures in solution. Resulting wires are characterized using transmission electron microscopy and possess mean ensemble diameters between 15 and 28 nm with accompanying lengths ranging from 4-10 μm. Subsequent solution-based overcoating chemistry results in ZnSe wires covered with CdSe nanocrystals. By varying the shell's growth time, different thicknesses can be obtained and range from 8 to 21 nm. More interestingly, the mean constituent CdSe nanocrystal diameter can be varied and results in size-dependent shell emission spectra.     

俄罗斯联邦城市郊区问题初探

近年来,俄罗斯联邦的政治经济体制经历了重大的变革,迅速改变了城市和农村的关系以及郊区的人口增长和发展模式。作为承载城市发展多种功能的特殊区域,俄罗斯联邦城市郊区的开发利用在这场变革中逐渐为人们所关注,且对于其郊区问题的研究具有重要的现实意义。本文分析了俄罗斯联邦城市郊区发展的政治经济背景和现状特点,从农业经济、规划建设、生态环境、休闲功能等不同角度分析了郊区发展存在的问题及原因,并针对现存问题展开了一些初步的建议性思考。     

The contribution of polyphenols to plant resistance to Pb soil pollution

This article considers the concentration of lead, polyphenols and water-soluble antioxidants (AOA) in the leaves of 4 species of woody, 11 species of shrub and 7 species of herbaceous plants growing in different functional zones in the city of Kaliningrad. The accumulations of Pb – the principal pollutant in urban ecosystems – were studied in the urban topsoil and plant leaves. An increase in Pb concentration in soils was associated with a decrease in AOA in tissues of the species examined. Changes in the background concentrations of antioxidants make it possible to estimate plant resistance to environmental stresses. The authors examine the contribution of polyphenols to the antioxidant potential of urban plants in soil polluted by Pb. The results obtained can be used to determine urban plant resistance to human impact and to improve the monitoring of industrial pollution in urban areas.     

NIR-Absorbing RuII Complexes Containing α-Oligothiophenes for Applications in Photodynamic Therapy

The design of near-infrared (NIR)-active photosensitizers (PSs) for light-based cancer treatments such as photodynamic therapy (PDT) has been a challenge. While several NIR-Ru^II scaffolds have been reported, this approach has not been proven in cells. This is the first report of NIR-Ru^II PSs that are phototoxic to cancer cells, including highly pigmented B16F10 melanoma cells. The PS family incorporated a bis(1,8-naphthyridine)-based ligand (tpbn), a bidentate thiophene-based ligand (nT; n=0–4), and a monodentate 4-picoline ligand (4-pic). All compounds absorbed light >800 nm with maxima near 730 nm. Transient absorption (TA) measurements indicated that n=4 thiophene rings ( 4T ) positioned the PDT-active triplet intraligand charge transfer (³ILCT) excited state in energetic proximity to the lowest-lying triplet metal-to-ligand charge transfer (³MLCT). 4T had low-micromolar phototoxicity with PI_vis and PI_733nm values as large as 90 and 12, respectively. Spectroscopic studies suggested that the longer-lived (τ_TA=3–6 μs) ³ILCT state was accessible from the ³MLCT state, but energetically uphill in the overall photophysics. The study highlights that phototoxic effects can be achieved with NIR-absorbing Ru^II PSs as long as the reactive ³ILCT states are energetically accessible from the low-energy ³MLCT states. It also demonstrates that tissue-penetrating NIR light can be used to activate the PSs in highly pigmented cells where melanin attenuates shorter wavelengths of light.     

Nucleoside Analogs and Perylene Derivatives Modulate Phase Separation of SARS-CoV-2 N Protein and Genomic RNA In Vitro

The life cycle of severe acute respiratory syndrome coronavirus 2 includes several steps that are supposedly mediated by liquid–liquid phase separation (LLPS) of the viral nucleocapsid protein (N) and genomic RNA. To facilitate the rational design of LLPS-targeting therapeutics, we modeled N-RNA biomolecular condensates in vitro and analyzed their sensitivity to several small-molecule antivirals. The model condensates were obtained and visualized under physiological conditions using an optimized RNA sequence enriched with N-binding motifs. The antivirals were selected based on their presumed ability to compete with RNA for specific N sites or interfere with non-specific pi–pi/cation–pi interactions. The set of antivirals included fleximers, 5′-norcarbocyclic nucleoside analogs, and perylene-harboring nucleoside analogs as well as non-nucleoside amphiphilic and hydrophobic perylene derivatives. Most of these antivirals enhanced the formation of N-RNA condensates. Hydrophobic perylene derivatives and 5′-norcarbocyclic derivatives caused up to 50-fold and 15-fold enhancement, respectively. Molecular modeling data argue that hydrophobic compounds do not hamper specific N-RNA interactions and may promote non-specific ones. These findings shed light on the determinants of potent small-molecule modulators of viral LLPS.     

Heterogeneous Manifestations of Epithelial–Mesenchymal Plasticity of Circulating Tumor Cells in Breast Cancer Patients

To date, there is indisputable evidence of significant CTC heterogeneity in carcinomas, in particular breast cancer. The heterogeneity of CTCs is manifested in the key characteristics of tumor cells related to metastatic progression – stemness and epithelial–mesenchymal (EMT) plasticity. It is still not clear what markers can characterize the phenomenon of EMT plasticity in the range from epithelial to mesenchymal phenotypes. In this article we examine the manifestations of EMT plasticity in the CTCs in breast cancer. The prospective study included 39 patients with invasive carcinoma of no special type. CTC phenotypes were determined by flow cytometry before any type of treatment. EMT features of CTC were assessed using antibodies against CD45, CD326 (EpCam), CD325 (N-cadherin), CK7, Snail, and Vimentin. Circulating tumor cells in breast cancer are characterized by pronounced heterogeneity of EMT manifestations. The results of the study indicate that the majority of heterogeneous CTC phenotypes (22 out of 24 detectable) exhibit epithelial–mesenchymal plasticity. The variability of EMT manifestations does not prevent intravasation. Co-expression of EpCAM and CK7, regardless of the variant of co-expression of Snail, N-cadherin, and Vimentin, are associated with a low number of CTCs. Intrapersonal heterogeneity is manifested by the detection of several CTC phenotypes in each patient. Interpersonal heterogeneity is manifested by various combinations of CTC phenotypes in patients (from 1 to 17 phenotypes).