Andrey M. Kovalskii

Boron Nitride Nanoparticles with a Petal-Like Surface as Anticancer Drug-Delivery Systems

Nanoparticles (NPs) have a great potential as nanosized drug-delivery carriers. Such systems must safely deliver the drug to the site of the tumor without drug leakage, effectively penetrate inside cancer cells, and provide intracellular drug release. Herein we developed an original and simple method aimed at the fabrication of spherical boron nitride NPs (BNNPs), 100-200 nm in diameter, with peculiar petal-like surfaces via chemical vapor deposition. Such structures were found to be able to absorb a large amount of antitumor drug-killing tumor cells. They revealed low cytotoxicity and rapid cellular uptake. BNNPs were saturated with doxorubicin (DOX) and then dispersed. The BNNPs loaded with DOX (BNNPs-DOX) were stable at neutral pH but effectively released DOX at pH 4.5-5.5. MTT assay and cell growth testing showed that the BNNPs-DOX nanocarriers had been toxic for IAR-6-1 cells. BNNPs loaded with DOX penetrated into the neoplastic IAR-6-1 cells using endocytic pathways, and then DOX released into the cytoplasm and cell nuclei and resulted in cell death.

Boron nitride nanotube growth via boron oxide-assisted chemical vapor transport-deposition process using LiNO3 as a promoter

High-purity straight and discrete multiwalled boron nitride nanotubes (BNNTs) were grown via a boron oxide vapor reaction with ammonia using LiNO3 as a promoter. Only a trace amount of boron oxide was detected as an impurity in the BNNTs by energy-dispersive X-ray (EDX) and Raman spectroscopies. Boron oxide vapor was generated from a mixture of B, FeO, and MgO powders heated to 1,150 °C, and it was transported to the reaction zone by flowing ammonia. Lithium nitrate was applied to the upper side of a BN bar from a water solution. The bar was placed along a temperature gradient zone in a horizontal tubular furnace. BNNTs with average diameters of 30–50 nm were mostly observed in a temperature range of 1,280–1,320 °C. At higher temperatures, curled polycrystalline BN fibers appeared. Above 1,320 °C, the number of BNNTs drastically decreased, whereas the quantity and diameter of the fibers increased. The mechanism of BNNT and fiber growth is proposed and discussed.

Effect of BN Nanoparticles Loaded with Doxorubicin on Tumor Cells with Multiple Drug Resistance

Herein we study the effect of doxorubicin-loaded BN nanoparticles (DOX-BNNPs) on cell lines that differ in the multidrug resistance (MDR), namely KB-3-1 and MDR KB-8-5 cervical carcinoma lines, and K562 and MDR i-S9 leukemia lines. We aim at revealing the possible differences in the cytotoxic effect of free DOX and DOX-BNNP nanoconjugates on these types of cells. The spectrophotometric measurements have demonstrated that the maximum amount of DOX in the DOX-BNNPs is obtained after saturation in alkaline solution (pH 8.4), indicating the high efficiency of BNNPs saturation with DOX. DOX release from DOX-BNNPs is a pH-dependent and DOX is more effectively released in acid medium (pH 4.0-5.0). Confocal laser scanning microscopy has shown that the DOX-BNNPs are internalized by neoplastic cells using endocytic pathway and distributed in cell cytoplasm near the nucleus. The cytotoxic studies have demonstrated a higher sensitivity of the leukemia lines to DOX-BNNPs compared with the carcinoma lines: IC50(DOX-BNNPs) is 1.13, 4.68, 0.025, and 0.14 μg/mL for the KB-3-1, MDR KB-8-5, K562, and MDR i-S9 cell lines, respectively. To uncover the mechanism of cytotoxic effect of nanocarriers on MDR cells, DOX distribution in both the nucleus and cytoplasm has been studied. The results indicate that the DOX-BNNP nanoconjugates significantly change the dynamics of DOX accumulation in the nuclei of both KB-3-1 and KB-8-5 cells. Unlike free DOX, the utilization of DOX-BNNPs nanoconjugates allows for maintaining a high and stable level of DOX in the nucleus of MDR KB-8-5 cells.

Single crystal growth, transport and scanning tunneling microscopy and spectroscopy of FeSe1−xSx

Single crystals of sulfur-substituted iron selenide, FeSe1−xSx, were grown within eutectics of molten halides, AlCl3/KCl, AlCl3/KCl/NaCl or AlCl3/KBr, under permanent temperature gradient. The innovative “ampoule in ampoule” design of a crystallization vessel allows obtaining mm-sized plate-like single crystals with a sulfur content up to x ∼ 0.19. The sharp anomalies in the physical properties indicate the superconducting and nematic phase transitions in FeSe0.96 at TC = 8.4 K and TN = 90 K, respectively. Scanning tunneling microscopy reveals the presence of dumbbell defects associated with Fe vacancies and dark defects at the chalcogen site associated with S within the FeSe1−xSx series of compounds. Scanning tunneling spectroscopy shows the presence of two different superconducting gaps at both hole and electron pockets of the Fermi surface for low S content levels. As a function of sulfur content, TC follows the conventional dome-shaped curve while TN decreases with x. The overall appearance of the T–x phase diagram of FeSe1−xSx suggests the importance of nematic fluctuations for the formation of the superconducting state in these compounds.

BN nanoparticle/Ag hybrids with enhanced catalytic activity: theory and experiments

Hexagonal boron nitride nanoparticles (BNNPs) with different amounts of boron oxide on their surfaces were used as catalyst carriers. BNNPs/Ag nanohybrids were produced via ultraviolet (UV) decomposition of AgNO3 in a mixture of polyethylene glycol and BNNPs. High temperature (1600 °C, 1.5 h) vacuum annealing of BNNPs promoted small size (5–10 nm) Ag nanoparticle (AgNPs) formation on BN surfaces with narrow size distribution, whereas using BNNPs in their as-produced state resulted in large AgNPs with various sizes. An increase in the B2O3 content on the BNNPs surfaces (up to a certain point) during BNNP pre-annealing in air led to larger amounts of AgNPs on their surfaces. Experimental results were confirmed by theoretical calculations of the adhesion energy of the (111)Ag with (0001)h-BN and (100)B2O3 surfaces. In contrast to the nonwettability of the h-BN surface by AgNPs, silver bound well to B2O3 with the formation of a covalent bond at the interface. Excessive fraction of B2O3, however, was not beneficial in terms of obtaining the optimal contents of AgNPs. Results of catalytic activity tests demonstrated that BNNPs/Ag nanohybrids synthesized using BNNPs with an optimized amount of B2O3 possess significantly enhanced catalytic activity compared to BNNPs without or with excess amounts of oxide. Finally, the catalytic activity of nanohybrids was theoretically analyzed using density functional theory (DFT) calculations.

BN/Ag hybrid nanomaterials with petal-like surfaces as catalysts and antibacterial agents

BN/Ag hybrid nanomaterials (HNMs) and their possible applications as novel active catalysts and antibacterial agents are investigated. BN/Ag nanoparticle (NP) hybrids were fabricated using two methods: (i) chemical vapour deposition (CVD) of BN NPs in the presence of Ag vapours, and (ii) ultraviolet (UV) decomposition of AgNO3 in a suspension of BN NPs. The hybrid microstructures were studied by high-resolution transmission electron microscopy (HRTEM), high-angular dark field scanning TEM imaging paired with energy dispersion X-ray (EDX) mapping, X-ray photoelectron spectroscopy (XPS), and infrared spectroscopy (FTIR). They were also characterized in terms of thermal stability, Ag+ ion release, catalytic and antibacterial activities. The materials synthesized via UV decomposition of AgNO3 demonstrated a much better catalytic activity in comparison to those prepared using the CVD method. The best catalytic characteristics (100% methanol conversion at 350 °C) were achieved using the UV BN/Ag HNMs without preliminary annealing at 600 °C in an oxidizing atmosphere. Both types of the BN/Ag HNMs possess a profound antibacterial effect against Escherichia coli K-261 bacteria.

Immobilization of Platelet-Rich Plasma onto COOH Plasma-Coated PCL Nanofibers Boost Viability and Proliferation of Human Mesenchymal Stem Cells

The scaffolds made of polycaprolactone (PCL) are actively employed in different areas of biology and medicine, especially in tissue engineering. However, the usage of unmodified PCL is significantly restricted by the hydrophobicity of its surface, due to the fact that its inert surface hinders the adhesion of cells and the cell interactions on PCL surface. In this work, the surface of PCL nanofibers is modified by Ar/CO2/C2H4 plasma depositing active COOH groups in the amount of 0.57 at % that were later used for the immobilization of platelet-rich plasma (PRP). The modification of PCL nanofibers significantly enhances the viability and proliferation (by hundred times) of human mesenchymal stem cells, and decreases apoptotic cell death to a normal level. According to X-ray photoelectron spectroscopy (XPS), after immobilization of PRP, up to 10.7 at % of nitrogen was incorporated into the nanofibers surface confirming the grafting of proteins. Active proliferation and sustaining the cell viability on nanofibers with immobilized PRP led to an average number of cells of 258 ± 12.9 and 364 ± 34.5 for nanofibers with ionic and covalent bonding of PRP, respectively. Hence, our new method for the modification of PCL nanofibers with PRP opens new possibilities for its application in tissue engineering.