Systematic rare Earth doping to adopt an R32 type huntite structure in NdSc3(BO3)4 crystals

This study is focused on determining the type and quantity of REE impurities responsible for converting the structure of NdSc3(BO3)4 into an R32 polymorph. According to the single crystal X-ray diffraction of RxNdyScz(BO3)4 (R = Sm-Lu, x + y + z = 4) the samples probably contain several polymorphic modifications. However, the predominant structure has been defined as R32 for R = Eu, Er, Tm, and Yb and P3221 for R = Sm, Gd, Tb, Dy, and Ho. Another potential limitation to the future use of the crystals is a compositional zoning found in the crystals with significant substitution in the scandium position.

Plasmonic Nanocomposites of ZnO-Ag Produced by Laser Ablation and Their Photocatalytic Destruction of Rhodamine, Tetracycline and Phenol

Hydrosphere pollution by organic pollutants of different nature (persistent dyes, phenols, herbicides, antibiotics, etc.) is one of the urgent ecological problems facing humankind these days. The task of water purification from such pollutants can be effectively solved with the help of modern photocatalytic technologies. This article is devoted to the study of photocatalytic properties of composite catalysts based on ZnO modified with plasmonic Ag nanoparticles. All materials were obtained by laser synthesis in liquid and differed by their silver content and preparation conditions, such as additional laser irradiation and/or annealing of produced powders. The prepared ZnO-Ag powders were investigated by electron microscopy, X-ray diffraction and UV-Vis spectroscopy. Photocatalytic tests were carried out with well- known test molecules in water (persistent dye rhodamine B, phenol and common antibiotic tetracycline) using LED light sources with wavelengths of 375 and 410 nm. The introduction of small concentrations (up to 1%) of plasmonic Ag nanoparticles is shown to increase the efficiency of the ZnO photocatalyst by expanding its spectral range. Both the preparation conditions and material composition were optimized to obtain composite photocatalysts with the highest efficiency. Finally, the operation mechanisms of the material with different distribution of silver are discussed.

Unraveling the Structural and Compositional Peculiarities in CTAB-Templated CeO2-ZrO2-MnOx Catalysts for Soot and CO Oxidation

Structure-performance relationships in functional catalysts allow for controlling their performance in a wide range of reaction conditions. Here, the structural and compositional peculiarities in CTAB-templated CeO2-ZrO2-MnOx catalysts prepared by co-precipitation of precursors and their catalytic behavior in CO oxidation and soot combustion are discussed. A complex of physical-chemical methods (low-temperature N2 sorption, XRD, TPR-H2, Raman, HR TEM, XPS) is used to elucidate the features of the formation of interphase boundaries, joint phases, and defects in multicomponent oxide systems. The addition of Mn and/or Zr dopant to ceria is shown to improve its performance in both reactions. Binary Ce-Mn catalysts demonstrate enhanced performance closely followed by the ternary oxide catalysts, which is due the formation of several types of active sites, namely, highly dispersed MnOx species, oxide-oxide interfaces, and oxygen vacancies that can act individually and/or synergistically.

Ni-Based SBA-15 Catalysts Modified with CeMnOx for CO2 Valorization via Dry Reforming of Methane: Effect of Composition on Modulating Activity and H2/CO Ratio

Dry reforming of methane with ratio CH4/CO2 = 1 is studied using supported Ni catalysts on SBA-15 modified by CeMnOx mixed oxides with different Ce/Mn ratios (0.25, 1 and 9). The obtained samples are characterized by wide-angle XRD, SAXS, N2 sorption, TPR-H2, TEM, UV-vis and Raman spectroscopies. The SBA-15 modification with CeMnOx decreases the sizes of NiO nanoparticles and enhances the NiO-support interaction. When Ce/Mn = 9, the NiO forms small particles on the surface of large CeO2 particles and/or interacts with CeO2, forming mixed phases. The best catalytic performance (at 650 °C, CH4 and CO2 conversions are 51 and 69%, respectively) is achieved over the Ni/CeMnOx/SBA-15 (9:1) catalyst. The peculiar CeMnOx composition (Ce/Mn = 9) also improves the catalyst stability: In a 24 h stability test, the CH4 conversion decreases by 18 rel.% as compared to a 30 rel.% decrease for unmodified catalyst. The enhanced catalytic stability of Ni/CeMnOx/SBA-15 (9:1) is attributed to the high concentration of reactive peroxo (O-) and superoxo (O2-) species that significantly lower the amount of coke in comparison with Ni-SBA-15 unmodified catalyst (weight loss of 2.7% vs. 42.2%). Ni-SBA-15 modified with equimolar Ce/Mn ratio or Mn excess is less performing. Ni/CeMnOx/SBA-15 (1:4) with the highest content of manganese shows the minimum conversions of reagents in the entire temperature range (X(CO2) = 4-36%, X(CH4) = 8-58%). This finding is possibly attributed to the presence of manganese oxide, which decorates the Ni particles due to its redistribution at the preparation stage.

Development of DNA Aptamers for Visualization of Glial Brain Tumors and Detection of Circulating Tumor Cells

Here, we present DNA aptamers capable of specific binding to glial tumor cells in vitro, ex vivo, and in vivo for visualization diagnostics of central nervous system tumors. We selected the aptamers binding specifically to the postoperative human glial primary tumors and not to the healthy brain cells and meningioma, using a modified process of systematic evolution of ligands by exponential enrichment to cells; sequenced and analyzed ssDNA pools using bioinformatic tools and identified the best aptamers by their binding abilities; determined three-dimensional structures of lead aptamers (Gli-55 and Gli-233) with small-angle X-ray scattering and molecular modeling; isolated and identified molecular target proteins of the aptamers by mass spectrometry; the potential binding sites of Gli-233 to the target protein and the role of post-translational modifications were verified by molecular dynamics simulations. The anti-glioma aptamers Gli-233 and Gli-55 were used to detect circulating tumor cells in liquid biopsies. These aptamers were used for in situ, ex vivo tissue staining, histopathological analyses, and fluorescence-guided tumor and PET/CT tumor visualization in mice with xenotransplanted human astrocytoma. The aptamers did not show in vivo toxicity in the preclinical animal study. This study demonstrates the potential applications of aptamers for precise diagnostics and fluorescence-guided surgery of brain tumors.

Unraveling the low-temperature activity of Rh-CeO2 catalysts in CO oxidation: probing the local structure and Red-Ox transformation of Rh3+ species

The local structure of the active sites is one of the key aspects of establishing the nature of the catalytic activity of the systems. In this work, a detailed structural investigation of the Rh-CeO₂ catalysts prepared by the co-precipitation method was carried out. The application of a variety of physicochemical methods such as XRD, Raman spectroscopy, XPS, TEM, TPR-H₂, and XAS revealed the presence of highly dispersed Rh³⁺ species in the catalysts: Rh³⁺ single ions and RhO_x clusters. The substitution of Ce⁴⁺ ions by Rh³⁺ species, which provided a strong distortion of the CeO₂ lattice, is shown. XAS data ensured the refinement of the Rh local structure. It was shown that single Rh³⁺ sites located next to each other can merge the formation of RhO_x clusters with Rh local environment close to the one in Rh₂O₃ and CeRh₂O₅ oxides. The distortion of the CeO₂ lattice around single and cluster rhodium species had a beneficial effect on the catalytic activity of the samples in low-temperature CO oxidation (LTO-CO). TEM, XAS, and in situ XRD data allowed establishing the structural transformations of the catalysts under Red-Ox treatments. The reduction treatment led to Rhn metallic cluster formation localized on defects of the reduced CeO_2-δ. The reduced sample demonstrated efficient CO conversion at 0 °C. However, this system was not stable: its contact with air led to ceria reoxidation and partial reoxidation of Rh to highly dispersed Rh³⁺ species at room temperature, while heating in an oxidizing atmosphere resulted in the complete reoxidation of metallic rhodium species. The results of the work shed light on the structural aspects of the reversibility of the Rh-CeO₂ catalysts based on the highly dispersed Rh³⁺ species under treatment in the reaction conditions.

Synthesis and Growth of Rare Earth Borates NaSrR(BO3)2 (R = Ho-Lu, Y, Sc)

NaSrR(BO₃)₂ (R = Ho-Lu, Y, Sc) compounds were obtained for the first time. Their structures exhibit disordered positions of Sr²⁺ and Na⁺ atoms while RO₆ polyhedra are connected through the BO₃ groups. Large distances between R atoms and high transparency in the range of 250-900 nm make them promising for phosphor applications. A pathway to obtain single crystals was shown by growing NaSrY(BO₃)₂ and NaSrYb(BO₃)₂ by the top seeded solution growth method with Na₂O-B₂O₃-NaF flux.

Structure- and Interaction-Based Design of Anti-SARS-CoV-2 Aptamers

Aptamer selection against novel infections is a complicated and time-consuming approach. Synergy can be achieved by using computational methods together with experimental procedures. This study aims to develop a reliable methodology for a rational aptamer in silico et vitro design. The new approach combines multiple steps: (1) Molecular design, based on screening in a DNA aptamer library and directed mutagenesis to fit the protein tertiary structure; (2) 3D molecular modeling of the target; (3) Molecular docking of an aptamer with the protein; (4) Molecular dynamics (MD) simulations of the complexes; (5) Quantum-mechanical (QM) evaluation of the interactions between aptamer and target with further analysis; (6) Experimental verification at each cycle for structure and binding affinity by using small-angle X-ray scattering, cytometry, and fluorescence polarization. By using a new iterative design procedure, structure- and interaction-based drug design (SIBDD), a highly specific aptamer to the receptor-binding domain of the SARS-CoV-2 spike protein, was developed and validated. The SIBDD approach enhances speed of the high-affinity aptamers development from scratch, using a target protein structure. The method could be used to improve existing aptamers for stronger binding. This approach brings to an advanced level the development of novel affinity probes, functional nucleic acids. It offers a blueprint for the straightforward design of targeting molecules for new pathogen agents and emerging variants.

Antibacterial Ferroelectric Hybrid Membranes Fabricated via Electrospinning for Wound Healing

In the present study, wound healing ferroelectric membranes doped with zinc oxide nanoparticles were fabricated from vinylidene fluoride-tetrafluoroethylene copolymer and polyvinylpyrrolidone using the electrospinning technique. Five different ratios of vinylidene fluoride-tetrafluoroethylene to polyvinylpyrrolidone were used to control the properties of the membranes at a constant zinc oxide nanoparticle content. It was found that an increase of polyvinylpyrrolidone content leads to a decrease of the spinning solution conductivity and viscosity, causing a decrease of the average fiber diameter and reducing their strength and elongation. By means of X-ray diffraction and infrared spectroscopy, it was revealed that increased polyvinylpyrrolidone content leads to difficulty in crystallization of the vinylidene fluoride-tetrafluoroethylene copolymer in the ferroelectric β-phase in membranes. Changing the ratio of vinylidene fluoride-tetrafluoroethylene copolymer and polyvinylpyrrolidone with a constant content of zinc oxide nanoparticles is an effective approach to control the antibacterial properties of membranes towards Staphylococcus aureus. After carrying out in vivo experiments, we found that ferroelectric hybrid membranes, containing from five to ten mass percent of PVP, have the greatest wound-healing effect for the healing of purulent wounds.

Development of Electrochemical Aptasensor for Lung Cancer Diagnostics in Human Blood

We describe the preparation and characterization of an aptamer-based electrochemical sensor to lung cancer tumor markers in human blood. The highly reproducible aptamer sensing layer with a high density (up to 70% coverage) on the gold electrode was made. Electrochemical methods and confocal laser scanning microscopy were used to study the stability of the aptamer layer structure and binding ability. A new blocking agent, a thiolated oligonucleotide with an unrelated sequence, was applied to fill the aptamer layer’s defects. Electrochemical aptasensor signal processing was enhanced using deep learning and computer simulation of the experimental data array. It was found that the combinations (coupled and tripled) of cyclic voltammogram features allowed for distinguishing between the samples from lung cancer patients and healthy candidates with a mean accuracy of 0.73. The capacitive component from the non-Faradic electrochemical impedance spectroscopy data indicated the tumor marker’s presence in a sample. These findings allowed for the creation of highly informative aptasensors for early lung cancer diagnostics.

Study of an EuBO3-ScBO3 system and EuSc3(BO3)4, EuSc(BO3)2 orthoborates

The EuBO₃-ScBO₃ system was investigated by solid state synthesis and DSC methods. In this system, a new EuSc(BO₃)₂ compound was found. It crystallizes in the R3̄ space group with unit cell parameters of a = 4.8939(1) Å and c = 16.2663(5) Å. Whereas another compound in the system EuSc₃(BO₃)₄ possesses two modifications: a low-temperature α-C2/c (a = 7.687(1) Å, b = 9.810(2) Å, c = 12.021(2) Å, and β = 105.379(4)°) and a high-temperature β-R32 (a = 9.7473(1) Å and c = 7.9205(2) Å). The α-EuSc₃(BO₃)₄ crystal was grown with LiBO₂-LiF flux, and β-EuSc₃(BO₃)₄ was obtained by the solid state synthesis. All of the obtained crystals exhibited typical Eu³⁺ luminescence spectra with peaks at 589 nm, 596 nm, 615 nm, 657 nm and 689 nm, which corresponded to the ⁵D₀ → ⁷F_J (J = 0, 1, 2 and 4) electron transitions. The strongest peak of luminescence was located at 615 nm and corresponded to the ⁵D₀ → ⁷F₀ transition.

In situ probing of Pt/TiO2 activity in low-temperature ammonia oxidation

NAP-XPS and operando XAS study of Pt/TiO₂ catalysts shows that Pt⁰ species stabilized on TiO₂ surface have the highest activity at low-temperature NH₃ oxidation.

Study of an SmBO3–ScBO3 system and new SmSc(BO3)2 orthoborate

A new SmSc(BO₃)₂ compound was discovered from the study of SmBO₃–ScBO₃ phase diagram.

Highly Defective Dark Nano Titanium Dioxide: Preparation via Pulsed Laser Ablation and Application

The development of methods to synthesize and study the properties of dark titania is of the utmost interest due to prospects for its use, primarily in photocatalysis when excited by visible light. In this work, the dark titania powder was prepared by pulsed laser ablation (Nd:YAG laser, 1064 nm, 7 ns) in water and dried in air. To study the changes occurring in the material, the thermal treatment was applied. The structure, composition, and properties of the obtained powders were studied using transmission electron microscopy, low-temperature N2 adsorption/desorption, X-ray diffraction, thermogravimetry/differential scanning calorimetry, X-ray photoelectron, Raman and UV-vis spectroscopies, and photoluminescence methods. The processes occurring in the initial material upon heating were studied. The electronic structure of the semiconductor materials was investigated, and the nature of the defects providing the visible light absorption was revealed. The photocatalytic and antibacterial activities of the materials obtained were also studied. Dark titania obtained via laser ablation in liquid was found to exhibit catalytic activity in the phenol photodegradation process under visible light (> 420 nm) and showed antibacterial activity against Staphylococcus aureus and bacteriostatic effect towards Escherichia coli.

Aptamer-Conjugated Superparamagnetic Ferroarabinogalactan Nanoparticles for Targeted Magnetodynamic Therapy of Cancer

Nanotechnologies involving physical methods of tumor destruction using functional oligonucleotides are promising for targeted cancer therapy. Our study presents magnetodynamic therapy for selective elimination of tumor cells in vivo using DNA aptamer-functionalized magnetic nanoparticles exposed to a low frequency alternating magnetic field. We developed an enhanced targeting approach of cancer cells with aptamers and arabinogalactan. Aptamers to fibronectin (AS-14) and heat shock cognate 71 kDa protein (AS-42) facilitated the delivery of the nanoparticles to Ehrlich carcinoma cells, and arabinogalactan (AG) promoted internalization through asialoglycoprotein receptors. Specific delivery of the aptamer-modified FeAG nanoparticles to the tumor site was confirmed by magnetic resonance imaging (MRI). After the following treatment with a low frequency alternating magnetic field, AS-FeAG caused cancer cell death in vitro and tumor reduction in vivo. Histological analyses showed mechanical disruption of tumor tissues, total necrosis, cell lysis, and disruption of the extracellular matrix. The enhanced targeted magnetic theranostics with the aptamer conjugated superparamagnetic ferroarabinogalactans opens up a new venue for making biocompatible contrasting agents for MRI imaging and performing non-invasive anti-cancer therapies with a deep penetrated magnetic field.

Development of DNA Aptamers to Native EpCAM for Isolation of Lung Circulating Tumor Cells from Human Blood

We selected DNA aptamers to the epithelial cell adhesion molecule (EpCAM) expressed on primary lung cancer cells isolated from the tumors of patients with non-small cell lung cancer using competitive displacement of aptamers from EpCAM by a corresponding antibody. The resulting aptamers clones showed good nanomolar affinity to EpCAM-positive lung cancer cells. Confocal microscopy imaging and spectral profiling of lung cancer tissues confirmed the same protein target for the aptamers and anti-EpCAM antibodies. Furthermore, the resulted aptamers were successfully applied for isolation and detection of circulating tumor cells in clinical samples of peripheral blood of lung cancer patients.

Comparative Study of Physicochemical and Antibacterial Properties of ZnO Nanoparticles Prepared by Laser Ablation of Zn Target in Water and Air

Here, we report on ZnO nanoparticles (NPs) generated by nanosecond pulsed laser (Nd:YAG, 1064 nm) through ablation of metallic Zn target in water and air and their comparative analysis as potential nanomaterials for biomedical applications. The prepared nanomaterials were carefully characterized in terms of their structure, composition, morphology and defects. It was found that in addition to the main wurtzite ZnO phase, which is conventionally prepared and reported by others, the sample laser generated in air also contained some amount of monoclinic zinc hydroxynitrate. Both nanomaterials were then used to modify model wound dressings based on biodegradable poly l-lactic acid. The as-prepared model dressings were tested as biomedical materials with bactericidal properties towards S. aureus and E. coli strains. The advantages of the NPs prepared in air over their counterparts generated in water found in this work are discussed.

Copper Nanoparticles for Ascorbic Acid Sensing in Water on Carbon Screen-printed Electrodes

A carbon screen-printed electrode was modified with copper nanoparticles from their dispersion obtained via pulsed laser ablation of a copper target in ethanol. The modified electrode exhibited activity in ascorbic acid electrochemical oxidation, giving an anodic current peak on voltammograms. Linear sweep and cyclic voltammetry have shown a linear dependence of the signal (both peak height and peak area) on the ascorbic acid concentration. The linear range from 1 to 250 μM of ascorbic acid was studied, and the detection limit was experimentally found to be 0.5 μM. The amperometric response to the addition of ascorbic acid portions into the solution was recorded. For the case of the simultaneous presence of ascorbic acid and glucose, two separate signal were obtained. Thus, the modified electrodes are characterized by the following advantages: disposable use; small amount of the samples required for the analysis; lower price (cheap copper is used); simple and easy modification procedure; good metrological characteristics; selectivity.

Dispersion properties of sulfur doped gallium selenide crystals studied by THz TDS

High optical quality nonlinear crystals of solid solution GaSe(1-x)S(x), x=0, 0.05, 0.11, 0.22, 0.29, 0.44, 1 were grown by modified Bridgman method with heat field rotation. Ordinary and extraordinary wave dispersion was studied in detail as a function of sulfur content by terahertz time-domain spectroscopy (THz TDS) in the 0.3-4 THz range using cleaved and processed (cut and polished) crystals. Suitable dispersion equations for different parts of the entire transparency range were derived, utilizing comparative analyses of the measured data, the available published data, and approximations in the form of Sellmeier equations. A criterion was proposed for selecting measurement results of adequate quality, based on the etalon patterns in the transmission spectrum.

Cloning and expression of genes coding for carbohydrate degrading enzymes of Anaerocellum thermophilum in E.coli

A gene library of Anaerocellum thermophilum Z-1320 was constructed in Escherichia coli using plasmid pUC18. Clones were selected by screening for hydrolysis of CMC, MU-Cel, lichenan and xylan. Recombinant clones expressing two beta-1,4-glucanases and two different xylanases were obtained. Both beta-1,4-glucanases were capable of degrading Avicel. Clones with xylanase activity also cleft PNPXyl, MU-Glu and MU-Cel. The genes of one beta-1,4-glucanase and one xylanase are probably located in the same region of A.thermophilum chromosome.

Cloning and expression in Escherichia coli of Thermotoga neapolitana genes coding for enzymes of carbohydrate substrate degradation

A genomic library of thermophilic anaerobic eubacterium Thermatoga neapolitana was constructed in E. coli using the pTZ19R plasmid vector. Some groups of recombinant clones with different cellulase activities were revealed: clones carrying genes for an 1,4-beta-glucanases, 1,3-beta-glucanases, beta-xylanases, beta-glucosidases and beta-xylosidases. One clone possessing avicelase activity was obtained. Some clones were selected with amylolytic activities toward amylose, amylopectin and pullulan.