Transmission Electron Microscopy Research Articles

Nano-optics of transition metal dichalcogenides and their van der Waals heterostructures with electron spectroscopies

Abstract The outstanding properties of transition metal dichalcogenide (TMD) monolayers and their van der Waals (vdW) heterostructures, arising from their structure and the modified electron-hole Coulomb interaction in two-dimension, make them promising candidates for potential electro-optical devices. However, the production of reproducible devices remains challenging, partly due to variability at the nanometer to atomic scales. Thus, access to chemical, structural, and optical characterization at these lengthscales is essential. While electron microscopy and spectroscopy can provide chemical and structural data, accessing the optical response at the nanoscale through electron spectroscopies has been hindered until recently. This review focuses on the application of two electron spectroscopies in scanning (transmission) electron microscopes, namely cathodoluminescence and electron energy-loss spectroscopy, to study the nano-optics of TMD atomic layers and their vdW heterostructures. How technological advancements that can improve these spectroscopies, many of which are already underway, will make them ideal for studying the physics of vdW heterostructures at the nanoscale will also be discussed.

Synthesis of nitrogen-doped carbon dot/ tin disulfide nanosheet composite electro-catalysts for dye-sensitized solar cells.

Nitrogen-doped carbon dots (N-CDs) and vertically-grown tin disulfide (SnS2) nanosheets are synthesized via hydrothermal method and chemical vapor deposition (CVD) technique, respectively. The SnS2 nanosheets are directly fabricated on flexible carbon cloth (CC), and then their basal planes are decorated with N-CDs. The as-prepared composite electrodes are used as the counter electrode for the application in dye-sensitized solar cells (DSSCs). The characterizations of N-CDs and SnS2 nanosheets are studied by high resolution transmission electron microscopy (HR-TEM), scanning electron microscopic (SEM), energy dispersive X-ray spectrometer (EDS), Raman spectrometer and X-ray photoelectron spectroscopy (XPS) ect. Moreover, the cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and photocurrent-density voltage (J-V) are utilized to understand the electro-catalytic performance of N-CDs/SnS2/CC composite counter electrode. The N-CDs/SnS2/CC composite electrode shows higher cathodic reduction current density and lower charge transfer resistance in CV and EIS measurements, respectively, as compared to those of the electrodes with N-CDs or SnS2 alone. Meanwhile, the DSSC using N-CDs/SnS2/CC exhibits cell efficiency (η) of 7.68%, which is higher than those of cells having SnS2/CC (η=7.54%) and N-CDs/CC (η=5.66%) counter electrodes, repectively; it also reaches 94% cell efficiency of the cell using Pt/CC counter electrode (η=8.15%). The design concept of the modification of the basal planes by defect-rich carbon dots (i.e., N-CDs) and highly-exposed edge sites (i.e., vertically-grown SnS2 nanosheets) makes promising route to enhance the performance of two-dimensional electro-catalysts.

Electrochemical Liquid Phase TEM in Aqueous Electrolytes for Energy Applications: the Role of Liquid Flow Configuration.

Electrochemical liquid phase transmission electron microscopy (EC-LPTEM) is an invaluable tool for investigating the structural and morphological properties of functional materials in electrochemical systems for energy transition. Despite its potential, standardized experimental protocols and a consensus on data interpretation are lacking, due to a variety of commercial and customized electrical and microfluidic configurations. Given the small size of a typical electrochemical cell used in these experiments, frequent electrolyte renewal is crucial to minimize local chemical alterations from reactions and radiolysis. This study explores the effects of modifying the flow configuration within the liquid cell under experimental conditions relevant for energy applications in aqueous-based electrolytes, revealing how changes in mass transport dynamics drastically influence the electrochemical response of the cell. Two different cell designs are compared: convection- and diffusion-governed. Ex situ and in situ comparative flow experiments show that the diffusion cell mitigates gas bubbles formation and improves removal of gaseous products. The electrodeposition of Zn nanostructures and the characterization of a Cu-based catalyst are presented as proof-of-concept experiments for energy storage and CO2 reduction reaction (CO2RR) applications, respectively. The reported findings demonstrate that controlling mass transport in the liquid cell setup is crucial to obtain reliable operando experimental electrochemical conditions.

Effect of Transferrin-Modified Fe3O4 Nanoparticle Targeted Delivery miR-15a-5p Combined With Photothermal Therapy on Lung Cancer.

Existing studies have shown that transferrin receptor (TfR) is highly expressed on the surface of lung cancer cells, and nanoparticles (NPs) have been widely used as delivery vehicles. The aim of this study was to investigate the effect of the targeted delivery of Fe3O4 NPs modified with transferrin (Tf) compared with photothermal treatment for lung cancer. The morphology and properties of Fe3O4 NPs modified with Tf were tested by internal morphological characterization experiments including transmission electron microscopy, particle size meter infrared spectrometer and other experiments. The delivery of materials was investigated by cell proliferation and apoptosis experiments, and western blot experiment was used to detect yes-associated protein 1(YAP1) protein expression changes after delivering miR-15a-5p. In addition, animal models were constructed to further explore the targeting properties of the material. The results demonstrated that the nanomaterial has good stability and targeting properties. Meanwhile, we also discovered that the miR-15a-5p carried by NPs can inhibit cell growth after its entry to the lung cancer cells. The effect became more evident when the nanomaterials were assisted with laser therapy, as verified by invivo and invitro experiments. In terms of the related mechanism, miR-15a-5p inhibited YAP1 expression, which affected cell proliferation and apoptosis. In this study, Fe3O4 NPs modified with Tf delivered miR-15a-5p in combination with photothermal therapy for lung cancer. In future research, the targeted delivery of Tf and the photothermal synergy of nanomaterials will provide a theoretical basis for cancer treatment.

In situ Fe-doped thin carbon wires via AC high voltage arc discharge

This study explores the controlled, continuous production of thin carbon rods between graphite electrodes (continued electrode deposits) during an arc discharge of high voltage alternating current with a frequency of 50 Hz in liquid paraffin, along with in situ doping of the resulting material using a suspension of liquid paraffin and iron powder ( <10 μm). The surface morphology of the obtained carbon rod nanomaterials was characterized using scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX), scanning transmission electron microscopy (STEM) with EDX chemical composition analysis, X-ray microtomography (micro-CT), and atomic force microscopy (AFM). The AFM technique in scanning thermal microscopy (SThM) and conductive probe (CP) modes was employed to determine the temperature and electrical conductivity of the obtained nanostructures. Qualitative analysis was conducted using Raman spectroscopy, X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). This simple system for producing thin, stable carbon wires (< 1.2 mm thick) enables efficient and low-cost production and doping of these materials. The high-voltage alternating current (HVAC) arc discharge method for growing controlled, metal-doped electrode deposits presents a new approach to producing inexpensive, porous carbon nanomaterials for various scientific and technological applications.

Scanning transmission electron tomography to study virus assembly: Review for the retirement of Paul Walther.

In this short and popular review, we summarise some of our findings analysing the replication cycles of large DNA viruses using scanning transmission electron tomography (STEM tomography) that we applied in the laboratory of Paul Walther. It is also a tribute to a very kind and expert scientist, who recently retired. Transmission electron microscopy (TEM), in particular cryo-EM, has benefited tremendously from recent developments in instrumentation. However, TEM imaging remains limited by the thickness of the specimen and classical thin-section TEM typically generates 2D representations of 3D volumes. Although TEM tomography can partly overcome this limitation, the thickness of the sample, the volume that can be analysed in 3D, remains limiting. STEM tomography can partly overcome this problem, as it allows for the analysis of thicker samples, up to 1 µm in thickness. As such, it is an interesting imaging technique to analyse large DNA viruses, some of which measure 1 µm or more, and which is the focus of our research interest.

Effects of Mandibular Advancement Device on Genioglossus of Rabbits in Obstructive Sleep Apnea Through PINK1/Parkin Pathway.

Early treatment of mandibular advancement device (MAD) reverses the abnormal changes resulting from obstructive sleep apnoea (OSA), but the underlying mechanism is not clear. We analysed the changes of genioglossus function before and after MAD treatment in OSA rabbits and explored the mechanism of mitochondrial autophagy. Eighteen male New Zealand rabbits were randomised into three groups: the control group, Group OSA, and Group MAD. After successful modelling, all animals were induced sleep in supine positions for 4-6 h per day for 8 weeks. Cone beam computed tomography (CBCT) and polysomnography (PSG) were performed to record sleep conditions. The genioglossus contractile force and the levels of LC3-I, LC3-II, Beclin-1, PINK1 and Parkin were detected in three groups. Invitro, C2C12 myoblast cells were cultured under normoxic or hypoxic conditions for 24 h, and then the changes in mitochondrial structure and accumulation of autolysosomes were detected by transmission electron microscopy (TEM). The contractile tension of the genioglossus in Group OSA was significantly lower than that in the control group. The ratio of LC3II/LC3I and the levels of Beclin-1, PINK1 and Parkin were higher in Group OSA than that in the control group. And the abnormal changes were tended to be normal after MAD treatment. The mitochondrial structure was disrupted, and the number of autolysosomes increased in C2C12 after 24 h of hypoxia. MAD treatment in male rabbits may decrease the contractile tension of the genioglossus and increase the level of mitochondrial autophagy caused by OSA. And the mechanism of mitochondrial autophagy was mediated by the PINK1/Parkin pathway in male rabbits.

Effects of miR-214-5p and miR-21-5p in hypoxic endometrial epithelial-cell-derived exosomes on human umbilical cord mesenchymal stem cells

BACKGROUND Thin endometrium seriously affects endometrial receptivity, resulting in a significant reduction in embryo implantation, and clinical pregnancy and live birth rates, and there is no gold standard for treatment. The main pathophysiological characteristics of thin endometrium are increased uterine arterial blood flow resistance, angiodysplasia, slow growth of the glandular epithelium, and low expression of vascular endothelial growth factor, resulting in endometrial epithelial cell (EEC) hypoxia and endometrial tissue aplasia. Human umbilical cord mesenchymal stem cells (HucMSCs) promote repair and regeneration of damaged endometrium by secreting microRNA (miRNA)-carrying exosomes. However, the initiation mechanism of HucMSCs to repair thin endometrium has not yet been clarified. AIM To determine the role of hypoxic-EEC-derived exosomes in function of HucMSCs and explore the potential mechanism. METHODS Exosomes were isolated from normal EECs (EEC-exs) and hypoxia-damaged EECs (EECD-exs), before characterization using Western blotting, nanoparticle-tracking analysis, and transmission electron microscopy. HucMSCs were cocultured with EEC-exs or EECD-exs and differentially expressed miRNAs were determined using sequencing. MiR-21-5p or miR-214-5p inhibitors or miR-21-3p or miR-214-5p mimics were transfected into HucMSCs and treated with a signal transducer and activator of transcription 3 (STAT3) activator or STAT3 inhibitor. HucMSC migration was assessed by Transwell and wound healing assays. Differentiation of HucMSCs into EECs was assessed by detecting markers of stromal lineage (Vimentin and CD13) and epithelial cell lineage (CK19 and CD9) using Western blotting and immunofluorescence. The binding of the miRNAs to potential targets was validated by dual-luciferase reporter assay. RESULTS MiR-21-5p and miR-214-5p were lowly expressed in EECD-ex-pretreated HucMSCs. MiR-214-5p and miR-21-5p inhibitors facilitated the migratory and differentiative potentials of HucMSCs. MiR-21-5p and miR-214-5p targeted STAT3 and protein inhibitor of activated STAT3, respectively, and negatively regulated phospho-STAT3. MiR-21-5p- and miR-214-5p-inhibitor-induced promotive effects on HucMSC function were reversed by STAT3 inhibition. MiR-21-5p and miR-214-5p overexpression repressed HucMSC migration and differentiation, while STAT3 activation reversed these effects. CONCLUSION Low expression of miR-21-5p/miR-214-5p in hypoxic-EEC-derived exosomes promotes migration and differentiation of HucMSCs into EECs via STAT3 signaling. Exosomal miR-214-5p/miR-21-5p may function as valuable targets for thin endometrium.

Green synthesis of Brassica carinata microgreen silver nanoparticles, characterization, safety assessment, and antimicrobial activities

Nanotechnology has been a central focus of scientific investigation over the past decades owing to its versatile applications. The synthesis of silver nanoparticles (AgNPs) through plant secondary metabolites is a cost-effective and eco-friendly approach. The present study employed Brassica carinata microgreen extracts (BCME) to promote the reduction of silver nitrate (AgNO3) salt into Brassica carinata microgreen silver nanoparticles (BCM-AgNPs). The physicochemical properties of the biosynthesized AgNPs were characterized through both spectroscopy and microscopy techniques. Furthermore, the antimicrobial property of the biosynthesized AgNPs was assessed against six selected pathogenic microorganisms, and finally, their safety was evaluated on a normal Vero cell line through an MTT cytotoxicity assay. The UV-visible spectrum revealed that BCM-AgNPs exhibited an absorption peak at 420 nm. The potential functional groups involved in the biosynthesis of AgNPs were identified by Fourier transform infrared (FTIR) analysis. Scanning electron microscopy (SEM) revealed a spherical nature of the biosynthesized AgNPs. Transmission electron microscopy (TEM) analysis revealed the crystallinity of the AgNPs, averaging 34.68 nm in size. X-ray diffraction (XRD) investigation further confirmed the crystalline structure of the AgNPs. The zeta potential exhibited a significant value of − 22.5 ± 1.16 mV. Regarding the antimicrobial potential, BCM-AgNPs exhibited promising antimicrobial activity against the tested pathogens, with a minimum inhibitory concentration (MIC) of 62.5 µg/mL observed in Pseudomonas aeruginosa. Further cytotoxicity assessment of BCM-AgNPs conducted on Vero cells demonstrated their safety. This study presents a novel approach to synthesizing AgNPs using a nutraceutical microgreen, offering a biocompatible and promising alternative for combating multi-drug resistance.

Evolution of precipitate and its effect on dislocation loops during in-situ He+ irradiation and annealing

The microstructural evolution of irradiation-induced point defects around the precipitates during in-situ 30 keV He+ irradiation was systematically investigated in Mo3Nb alloy using transmission electron microscopy (TEM) at various temperatures: room temperature (RT), 573 K, and 1073 K. The average size and volume number density of dislocation loops were obtain under the influence of irradiation temperature, fluence and different types (sizes and shapes) of precipitates. The irradiated defects showed distinct characteristics that correlated with the precipitate types. Dislocation loops of larger size and lower density were observed around the larger precipitates, which were also influenced by the precipitate morphology. Temperature had a great effect on defect migration, resulting in a decrease in loop density and an increase in loop size. Furthermore, the hardening effect attributed to irradiation-induced loops decreased with the increase of temperature and precipitate size. The dissolution of precipitates became increasingly pronounced with the increase of temperature, and irradiation could accelerate the process. At 573 K, the dissolution was only found in the large non-spherical precipitate, while at 1073 K, all the precipitates underwent dissolution. The annealing experiment conducted at 1073 K showed that the dissolution of large-sized precipitates would lead to the dispersion of small-sized precipitates, which was beneficial to increase the interfaces and potentially improve the radiation tolerance and mechanical properties of the alloy.

Magnetically-assembled multifunctional Fe3O4@SiO2@Au particles for SERS detection of low-concentration dye molecules

Abstract Surface-enhanced Raman scattering (SERS) is a sensitive spectroscopic method to detect low concentration-low volume analytes. Owing to this, there has been a rising interest in developing improved as well as novel nanostructured substrates for SERS applications. For SERS applications, it is desirable to have large-scale assemblies of such nanostructures that can sustain multiple electromagnetic ‘hotspots’ for improved sensitivity. In this work, we use magnetic-field aided large-scale assembly of multifunctional magnetic-plasmonic particles to generate a large area SERS substrate. The particles, composed of a Fe3O4 core with a thin silica coating followed by Au nanoparticles (Fe3O4@SiO2@Au), were synthesized by simple chemical methods. The multifunctional particles were characterized using powder x-ray diffraction, transmission electron microscopy, Raman spectroscopy, and SQUID magnetometer. Magnetic assembly of the composite particles, carried out using a bi-electromagnet setup, was used for SERS detection of organic dyes such as rhodamine B and methylene blue. Using this scheme, it was possible to detect ultra-low concentrations (up to 1fM) of the dye molecules. This method is promising for applications such as chemical sensors, biomolecular detection, cancer detection, and hyperthermia treatment, forensic investigations, and drug delivery.

Formation mechanisms of product film on high corrosion resistant EW75 Mg alloy: The effect of corrosive media

Compact and uniform product films with the similar microstructure as magnesium substrate are formed on EW75 alloy in both NaCl and Na2SO4 solution, and the film growth rate in Na2SO4 was even faster than that in the higher corrosive NaCl. This special phenomenon was investigated by electrochemical measurements, transmission electron microscopy (TEM) observation and X-ray diffraction (XRD) analysis, experimental design of corrosive media with different conductivity and concentration was used, and the corrosion process of Mg matrix and Mg-RE precipitates was explored, respectively. The results show that compared with Cl-, SO42- exhibits the stronger binding trend with Mg2+/RE3+, resulting in the faster charge transfer of the anodic metal in SO42- containing solution. And the higher dissolution rate of Mg substrate in Na2SO4 solution promotes the formation of the product film.

Comparison of rose bengal-green light scleral crosslinking in rabbit eyes using different infiltration protocols - An Ex Vivo study

Different concentrations and infiltration times of rose bengal (Rb) were assessed for their impact on penetration depth and crosslinking efficacy in rabbit sclera. Fresh rabbit eyes were used. Rb solution with concentrations of 0.1%–0.9% were applied for 5–30 min to infiltrate the sclera. The penetration depth of Rb was observed with confocal microscopy. After infiltration, the sclera was irradiated by green light for crosslinking. The sclera's biomechanical stiffness and the resistance to enzyme digestion post-treatment were evaluated. Histopathological analysis and transmission electron microscopy were performed to observe the morphology. As the infiltration time increased, the penetration depth and the fluorescence intensity of the Rb in sclera increased. After 32 h, 48.6% of the scleral tissue was undissolved in the 0.5% Rb-10min group, followed by the 0.1% Rb-20min group (13.8%) and 0.05% Rb-30min group (7.7%). At 8% strain, the Young's modulus of the 0.05%Rb-30min, the 0.1% Rb-20min and the 0.5% Rb-10min group were respectively 1.77, 2.45 and 3.19 times greater than that of the untreated group. There were no morphological differences between the experimental group and the untreated group. RG-SXL significantly increased the diameter of large collagen fibers in the middle and inner layers of the sclera. Ultimately, 0.5% Rb infiltration for 10 min achieves an appropriate infiltration depth and crosslinking effect, and may thus be a feasible schedule for scleral crosslinking.

Design and synthesis of camphor-thiazole derivatives as potent antifungal agents: structure-activity relationship and preliminary mechanistic study.

Plant pathogenic fungi pose a severe threat to crop yield and food security. This study aims to investigate the potential antifungal activity and mechanism of action of camphor-thiazole derivatives against six plant pathogenic fungi. A novel series of camphor-thiazole derivatives were designed, synthesized and evaluated for their antifungal effects against Rhizoctonia solani, Fusarium graminearum, Valsa mali, Alternaria solani, Colletotrichum orbiculare and Botryitis cinerea. Most of the synthesized camphor-thiazole derivatives exhibited notable antifungal activity. Amongst them, compounds C5, C10 and C17 showed significant activity against R. solani with median effective concentrations (EC50) values in the range 3-4 μg mL-1, demonstrating superior antifungal efficacy to the control drug boscalid (EC50 = 1.23 μg mL-1). Structure-activity relationship and density functional theory analysis emphasized the critical role of substituent selection in optimizing the biological activity of these compounds. Moreover, preliminary mechanistic studies revealed that compound C5 induced abnormal mycelial and cellular morphology in R. solani as observed using scanning and transmission electron microscopy, and triggered the production and accumulation of reactive oxygen species. Additionally, the increased concentration of C5 resulted in enhanced cell membrane permeability. In this study, the designed and optimized compound C5 emerged as a promising candidate for potent antifungal agents. The results demonstrate that synthesized camphor-thiazole derivatives possess potent antifungal activity and can serve as lead compounds for further optimization in antifungal agent development. © 2024 Society of Chemical Industry.

Orientation-related shear banding mediated deformation of Sm2Co17-type magnet

The service life and reliability of Sm2Co17-type permanent magnets in high-temperature energy conversion fields are significantly deteriorated due to their mechanical fragility. Herein, the deformation mechanisms of a strongly anisotropic Sm2Co17-type magnet are probed. Nanoindentation results suggest a weak anisotropy of hardness while a strong anisotropy of incipient plasticity related to crystal orientations, namely the nucleation of atomic shear bands working as plastic carriers is the easiest on {101̅0} planes but most difficult on {0001} planes. A statistical model on the critical shear stress of incipient plasticity indicates that the generation of shear band embryos is mainly processed via homogeneous nucleation from bond breakage. Transmission electron microscopy and ab initio calculations confirm that atomic bands along the pyramidal {011̅1} or basal {101̅0} planes primarily accommodate the deformation for loading direction along or perpendicular to the c-axis, respectively. The thickness of the {011̅1} and {101̅0} shear bands are in the range of 2–4 atomic layers. Nevertheless, due to the blocking effects of 1:3R Z-platelets and 2:17R twins on the progress of {011̅1} shear bands, the lengths of {011̅1} shear bands are much shorter than {101̅0} bands. Our work offers insights into the atomic-scale deformation mechanisms of Sm2Co17-type magnets.

Green Synthesis of Silver Nanoparticles Using Sclerorhachis Leptoclada Rech. F. Leaf Extract: Characterization and Investigation of Antibacterial Activities

Introduction: The environmentally friendly method of green nanoparticle production has garnered significant interest because of its cost-effectiveness and ease of implementation. In this study, in addition to the green synthesis of silver nanoparticles using the leaf extract of the Sclerorhachis leptoclada Rech. f. (SLL@AgNPs) and the morphological study of the SLL@AgNPs, the antibacterial properties of the SLL@AgNPs were compared with the extract of the S. leptoclada plant and silver nanoparticles alone. Methods: In this experimental investigation, the features of SLL@AgNPs synthesized via a green method were analyzed using various techniques, including spectrophotometry, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), dynamic light scattering (DLS), and transmission electron microscopy (TEM). Ultimately, the antibacterial properties were assessed through the broth micro-dilution method. Results: DLS and zeta potential showed the formation of SLL@AgNPs with a hydrodynamic diameter of 130 nm and a surface charge of -38.82 mV, respectively. XRD and TEM analysis also confirmed the formation of pure silver nanoparticles with spherical and elliptical morphology with an average diameter of 20-30. The SLL@AgNPs exhibited antibacterial activity against Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, and Enterococcus faecalis, with minimum inhibitory concentrations (MIC) of 0.039, 0.078, 0.039, 0.078, and 0.31 mg/ml, respectively. These findings indicate that SLL@AgNPs significantly enhanced the antibacterial properties of the S. leptoclada plant. Conclusion: As evidenced by the obtained results, S. leptoclada plant extract significantly increased the antibacterial activity of silver nanoparticles. This research demonstrated the potential of environmentally friendly silver nanoparticles synthesized in the presence of S. leptoclada extract with significant antibacterial effects for various biomedical applications.

Atomic behaviors in PdRu solid-solution nanoparticles on CeO2-ZrO2 support for the three-way catalytic reaction

Understanding the behavior of noble-metal catalysts is a key point of catalysis research aimed at reducing the environmental and economic costs associated with the increased use of automobiles. In this study, the atomic-behaviors of Ru and Pd atoms in PdRu solid-solution nanoparticles (NPs) supported on CeO2-ZrO2 (CZ) as a Rh-free three-way catalyst in a modeled three-way catalytic reaction (TWCR) were elucidated using a gas conversion analysis, transmission electron microscopy, and in-situ X-ray absorption fine structure spectroscopy. We found that the PdRu NPs enlarged by the annealing effect separated a smaller grain size with the Pd-rich and Ru-rich phase under TWCR. Most of the oxidation and reduction reactions under the modeled TWCR occurred on the Ru. However, the Pd metals acted as a major role of the reduction of NO gas and oxidation of CO and C3H6 gas. Ru atoms just is a minor role during the modeled TWCR. This study demonstrates the potential of PdRu NPs as a three-way catalyst and reveals the atomic-behavior and catalytic role under the modeled TWCR.

Bacillus subtilis, a promising bacterial candidate for trapping nanoplastics during water treatment

As a probiotic, Bacillus subtilis (B. subtilis) has a wide range of application values. In this study, the trap by B. subtilis and the effect of NPs on its growth physiology were studied. Confocal laser scanning microscopy (LCSM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed that PS-NPs were trapped by B. subtilis when they were exposed to PS-NPs. At this point, most of the PS-NPs are clustered around B. subtilis. Flow cytometry showed that at 10 mg/L, 73.7 % of PS-NPs' environmental state changed. The complexity of 9.73 %, 23.77 %, 43.27 %, and 65.13 % of B. subtilis increased at PS-NP concentrations of 10, 20, 50, and 200 mg/L, respectively. The increase in overall EPS secretion ranged from 0.51 ∼ 7.13 μg/mL after adding different concentrations of PS-NPs. The effect of different concentrations of PS-NPs on NAR activity ranged from −11.38 ∼ 16.2 %, on NIR activity from −17.90 ∼ 7.22 %, on NOR activity from −15.10 ∼ 7.69 % and on NO2R activity from −14.01 ∼ 17.03 %. These results indicated that B. subtilis can process nitrogen compounds in water while capturing NPs in the environment. They have the potential to be candidate bacteria in the water treatment process, and specific applications are needed to research further.

Preparation of water-soluble CdSeS alloy quantum dots with small particle size and high fluorescence lifetime by using hydrodynamic cavitation technology and their application in Ag+ detection

In this study, hydrodynamic cavitation (HC) is used as a novel and simple large-scale preparation technique. Water-soluble CdSeS alloy quantum dots (QDs) were successfully prepared by using Cd(NO3)2·4H2O, Na2S·9H2O and selenium powder as cadmium, sulfur and selenium sources. The effects of cycle time, reaction temperature, inlet pressure and Se/S molar ratio on the morphology, size and optical properties of CdSeS QDs were investigated. The prepared CdSeS QDs were characterized by X-ray diffractometer, X-ray photoelectron spectroscopy, transmission electron microscopy, UV–vis absorption spectra, fluorescence emission spectra and fluorescence attenuation curves. Finally, under the conditions of 12 h cycle time, 3.0 bar inlet pressure, 60 °C reaction temperature and 0.5/0.5 Se/S molar ratio, the ternary alloy CdSeS QDs with 2.62 nm average particle size and 482.62 ns fluorescence lifetime was obtained. Furthermore, a mechanism of preparing CdSeS QDs by using the HC method was proposed to explain the process of CdSeS precipitates conversion to CdSeS QDs. In addition, it is also found that Ag+ has a quenching effect on the prepared CdSeS QDs, which means that CdSeS QDs can be used as a fluorescence probe to specifically detect Ag+. This work not only provides a new possibility for large-scale preparation of high-performance QDs but also helps to understand the mechanism of CdSeS QDs as a metal ion selective fluorescence probe.

Exosomes secreted from human-derived adipose stem cells prevent progression of osteonecrosis of the femoral head

BackgroundOsteonecrosis of the femoral head (ONFH) primarily affects young individuals and is a leading cause of total hip arthroplasty in this population. Joint-preserving regenerative therapies involving core decompression (CD), enhanced with cells, growth factors, and bone substitutes, have been developed but lack extensive validation. Exosomes are emerging as a promising regenerative therapy. Human adipose stem cell (hADSC)-derived exosomes exhibit angiogenic and wound-healing effects on damaged and diseased tissues, suggesting their potential efficacy in treating early-stage ONFH. We aimed to investigate the efficacy of hADSC-derived exosomes based on CD in a medium-sized animal model (rabbit).MethodsExosomes were extracted using the ultrafiltration filter technique from the culture supernatants of two types of hADSCs. Characterization of exosomes was performed through nanoparticle tracking analysis, transmission electron microscopy, and the detection of specific biomarkers (CD9, CD63, and CD81) by western blotting. Eighteen rabbits underwent surgical vascular occlusion and intramuscular corticosteroid injections to induce ONFH. Concurrently, CD treatment with local administration of hADSC-derived exosomes (exosome group) or saline (control group) was performed. Femoral heads were harvested at 4, 8, and 12 weeks postoperatively and evaluated using micro-computed tomography and tissue staining to assess the protective effects on osteonecrosis, angiogenesis, and osteogenesis.ResultsExosomes had average particle concentrations of 1.8 × 1012 or 1.8 × 109 particles/mL, with particle size distributions averaging 61.2 ± 14.7 or 123.1 ± 46.3 nm, and were confirmed by specific biomarkers. The exosome group exhibited a significant reduction in the severe progression of ONFH to stages 3 or 4 of the modified Ficat and Arlet classification, compared to the control group, which had four cases of stages 3 or 4. The exosome group showed significantly fewer empty lacunae in the subchondral bone area (p < 0.05) and significantly less articular cartilage injury (p < 0.05) compared to the corresponding in the control group. There were no significant differences in the microvessel number, bone trabecular structure, or volume of new bone in the medial region of the CD.ConclusionshADSC-derived exosomes can prevent the progression of ONFH by inhibiting osteonecrosis and cartilage damage. The ultrafiltration filter technique is effective for exosome extraction, indicating that exosomes hold potential as a therapeutic agent for ONFH.