Effects of Glutamine Synthetase on Neovascularization in Glioma: In Vivo MR Vessel Size Imaging and Histology.

BACKGROUND: Glutamine Synthetase (GS) could induce vascular sprouting through the improvement of endothelial cell migration in inflammatory diseases. MR vessel-size imaging has been proposed as a valuable approach for visualizing the underlying angiogenic processes in the brain. OBJECTIVE: This study aims to investigate the role of GS in the neovascularization of gliomas through the utilization of MR vessel-size imaging and histopathological techniques. METHODS: In this exploratory animal study, we randomly divided the C6 glioma rat models into a control group and an L-methionine sulfoximine (MSO) treatment group. Daily intraperitoneal injections were administered for three consecutive days, starting from day 10 following the implantation of C6 glioma cells in rats. Subsequently, MR vessel size imaging was conducted using a BRUKER 7 T/200 mm MRI scanner, and the MRI results were validated through histopathological examination. RESULTS: A significant decrease in microvessel density was observed in both the tumor periphery and center areas in the MSO treatment group compared to that in the control group. The mean vessel diameter (mVD) and vessel size index (VSI) did not exhibit significant changes compared to the control group. Moreover, the staining intensity of platelet endothelial cell adhesion molecule-1 (CD31) and GS in the tumor periphery was significantly decreased in the MSO treatment group. Additionally, the MSO treatment demonstrated a substantial inhibition of tumor growth. CONCLUSION: GS inhibitors significantly reduced angiogenesis in the periphery area of C6 glioma, exerting an inhibitory effect on tumor progression. Thus, GS inhibitors could be potential therapeutic agents for treating glioma. Additionally, in vivo MR vessel size imaging detects changes in vascularrelated parameters after tumor treatment, making it a promising method for detecting neovascularization in glioma.

Tumor Microenvironment-Activated Nanostructure to Enhance MRI Capability and Nanozyme Activity for Highly Tumor-Specific Multimodal Theranostics.

Copper-based nanozymes exhibit excellent antitumor activity but are easily inactivated due to the disturbance of proteins or other macromolecules with sulfhydryl. A tumor microenvironment-responsive CuMnO@Fe3O4 (CMF) core-shell nanozyme for highly efficient tumor theranostics is developed. A platelet-derived growth factor receptor-ß-recognizing cyclic peptide (PDGFB) target is conjugated to the surface of CMF to fabricate a tumor-specific nanozyme (PCMF). The core-shell nanostructure significantly avoids the oxidation and inactivation of copper-based nanozyme, promoting the antitumor activity of PCMF. The weak acid- and GSH-activated T1 and T2 relaxation rate of PCMF contributes to T1 and T2 dual contrast imaging at the tumor site. In addition, the PCMF disintegrates and produces some metal ions that possess Fenton catalytic activity (i.e., Cu+, Mn2+, and Fe2+) under TME. This process significantly depletes GSH, accelerates Fenton and Fenton-like reactions, enhances cellular reactive oxygen species (ROS) levels, and induces cancer cell apoptosis and ferroptosis. PCMF also exhibits photothermal functions, so it can be used in combined photothermal therapy, ferroptosis therapy, and chemodynamic therapy, improving anticancer activity. This work provides insights into the design of an exquisite nanostructure for high-sensitive and tumor-specific theranostics.

Promoting ordering degree of intermetallic fuel cell catalysts by low-melting-point metal doping.

Carbon supported intermetallic compound nanoparticles with high activity and stability are promising cathodic catalysts for oxygen reduction reaction in proton-exchange-membrane fuel cells. However, the synthesis of intermetallic catalysts suffers from large diffusion barrier for atom ordering, resulting in low ordering degree and limited performance. We demonstrate a low-melting-point metal doping strategy for the synthesis of highly ordered L10-type M-doped PtCo (M = Ga, Pb, Sb, Cu) intermetallic catalysts. We find that the ordering degree of the M-doped PtCo catalysts increases with the decrease of melting point of M. Theoretic studies reveal that the low-melting-point metal doping can decrease the energy barrier for atom diffusion. The prepared highly ordered Ga-doped PtCo catalyst exhibits a large mass activity of 1.07 A mgPt-1 at 0.9 V in H2-O2 fuel cells and a rated power density of 1.05 W cm-2 in H2-air fuel cells, with a Pt loading of 0.075 mgPt cm-2.

Facile design of surface electric field driven tourmaline/g-C3N4 layered stacked photocatalysts with enhanced photocatalytic activity for antibiotic removal.

In the field of photocatalysis, Graphitic carbon nitride (g-C3N4) has received a lot of attention for its superior functionality and benefits. However, it suffers from the fatal defect of low charge separation efficiency, which is well addressed by tourmaline's self-contained surface electric field. In this work, tourmaline/g-C3N4 (T/CN) composites were successfully synthesized. Due to its surface electric field effect, tourmaline and g-C3N4 are stacked on top of each other. It makes its specific surface area increase greatly and more active sites are exposed. Additionally, the rapid separation of photogenerated electron holes under the action of electric field promotes the photocatalytic reaction. T/CN exhibited excellent photocatalytic performance under visible light, with 99.9% Tetracycline (TC 50 mg L-1) removal after 30 min. Compared to tourmaline (0.0160 min-1) and g-C3N4 (0.0230 min-1), the T/CN composite's reaction rate constant (0.1754 min-1) was 11.0 and 7.6 times higher. A series of characterizations also determined the structural properties and catalytic performance of the T/CN composites, which were found to have a larger specific surface area, narrower band gap, and higher charge separation efficiency compared to the monomer. In addition, the toxicity of tetracycline intermediates and their degradative pathways were investigated, and the toxicity of the intermediates was found to be reduced. Given the quenching experiments and active substance determination, it was also found that h+ and ·O2- play a major role. This work provides more inspiration for photocatalytic material performance research as well as green innovation for environmental management.

PDGFB-targeted functional MRI nanoswitch for activatable T1-T2 dual-modal ultra-sensitive diagnosis of cancer.

As one of the most significant imaging modalities currently available, magnetic resonance imaging (MRI) has been extensively utilized for clinically accurate cancer diagnosis. However, low signal-to-noise ratio (SNR) and low specificity for tumors continue to pose significant challenges. Inspired by the distance-dependent magnetic resonance tuning (MRET) phenomenon, the tumor microenvironment (TME)-activated off-on T1-T2 dual-mode MRI nanoswitch is presented in the current study to realize the sensitive early diagnosis of tumors. The tumor-specific nanoswitch is designed and manufactured on the basis of PDGFB-conjugating ferroferric oxide coated by Mn-doped silica (PDGFB-FMS), which can be degraded under the high-concentration GSH and low pH in TME to activate the T1-T2 dual-mode MRI signals. The tumor-specific off-on dual-mode MRI nanoswitch can significantly improve the SNR and is used successfully for the accurate diagnosis of early-stage tumors, particularly for orthotopic prostate cancer. In addition, the systemic delivery of the nanoswitch did not cause blood or tissue damage, and it can be excreted out of the body in a timely manner, demonstrating excellent biosafety. Overall, the strategy is a significant step in the direction of designing off-on dual-mode MRI nanoprobes to improve imaging accuracy, which opens up new avenues for the development of new MRI probes.

Non-iridium-based electrocatalyst for durable acidic oxygen evolution reaction in proton exchange membrane water electrolysis.

Iridium-based electrocatalysts remain the only practical anode catalysts for proton exchange membrane (PEM) water electrolysis, due to their excellent stability under acidic oxygen evolution reaction (OER), but are greatly limited by their high cost and low reserves. Here, we report a nickel-stabilized, ruthenium dioxide (Ni-RuO2) catalyst, a promising alternative to iridium, with high activity and durability in acidic OER for PEM water electrolysis. While pristine RuO2 showed poor acidic OER stability and degraded within a short period of continuous operation, the incorporation of Ni greatly stabilized the RuO2 lattice and extended its durability by more than one order of magnitude. When applied to the anode of a PEM water electrolyser, our Ni-RuO2 catalyst demonstrated >1,000 h stability under a water-splitting current of 200 mA cm-2, suggesting potential for practical applications. Density functional theory studies, coupled with operando differential electrochemical mass spectroscopy analysis, confirmed the adsorbate-evolving mechanism on Ni-RuO2, as well as the critical role of Ni dopants in stabilization of surface Ru and subsurface oxygen for improved OER durability.

Small molecule-assisted synthesis of carbon supported platinum intermetallic fuel cell catalysts.

Supported ordered intermetallic compounds exhibit superior catalytic performance over their disordered alloy counterparts in diverse reactions. But the synthesis of intermetallic compounds catalysts often requires high-temperature annealing that leads to the sintering of metals into larger crystallites. Herein, we report a small molecule-assisted impregnation approach to realize the general synthesis of a family of intermetallic catalysts, consisting of 18 binary platinum intermetallic compounds supported on carbon blacks. The molecular additives containing heteroatoms (that is, O, N, or S) can be coordinated with platinum in impregnation and thermally converted into heteroatom-doped graphene layers in high-temperature annealing, which significantly suppress alloy sintering and insure the formation of small-sized intermetallic catalysts. The prepared optimal PtCo intermetallics as cathodic oxygen-reduction catalysts exhibit a high mass activity of 1.08 A mgPt-1 at 0.9 V in H2-O2 fuel cells and a rated power density of 1.17 W cm-2 in H2-air fuel cells.

Resonant Lasing Emission in Undoped and Mg-Doped Gallium Nitride Thin Films on Interfacial Periodic Patterned Sapphire Substrates.

In this work, low-threshold resonant lasing emission was investigated in undoped and Mg-doped GaN thin films on interfacial designed sapphire substrates. The scattering cross-section of the periodic resonant structure was evaluated by using the finite difference time domain (FDTD) method and was found to be beneficial for reducing the threshold and enhancing the resonant lasing emission within the periodic structures. Compared with undoped and Si-doped GaN thin films, p-type Mg-doped GaN thin films demonstrated a better lasing emission performance. The lasing energy level system and defect densities played vital roles in the lasing emission. This work is beneficial to the realization of multifunctional applications in optoelectronic devices.

Intermetallic PtFe Electrocatalysts for the Oxygen Reduction Reaction: Ordering Degree-Dependent Performance.

Platinum-based atomically ordered alloys (i.e., intermetallic compounds) have distinct advantages over disordered solid solution counterparts in boosting the cathodic oxygen-reduction reaction (ORR) in proton-exchange-membrane fuel cells. Nevertheless, the pivotal role of ordering degree of intermetallic catalysts in promoting ORR performance has been ignored heavily so far, probably owing to the lack of synthetic routes for controlling the ordering degree, especially for preparing highly ordered intermetallic catalysts. Herein, a family of intermetallic PtFe catalysts with similar particle size of 3-4 nm but varied ordering degree in a wide range of 10-70% are prepared. After constructing the PtFe/Pt core/shell structure with around 3 Pt-layer skin, a positive correlation between the ordering degree of the intermetallic catalysts and their ORR activity and durability is identified. Notably, the highly ordered PtFe/Pt catalyst exhibits a high mass activity of 0.92 A mgPt -1 at 0.9 ViR-corrected as cathode catalyst in H2 -O2 fuel cell, with only 24% loss after accelerated durability tests. The ordering degree-dependent performance can be ascribed to the compressive strain effect induced by the intermetallic PtFe core with smaller lattice parameters, and the more thermodynamically stable intermetallic structure compared to disordered alloys.

Ordering Degree-Dependent Activity of Pt3M (M = Fe, Mn) Intermetallic Nanoparticles for Electrocatalytic Methanol Oxidation.

Atomically ordered intermetallic alloys with unique electronic and geometrical structures are highly attractive for heterogeneous catalysis and electrocatalysis. However, the formation of intermetallic phases generally requires high-temperature annealing to overcome the kinetic energy barrier of atom ordering, which unfortunately causes high material heterogeneity and thus makes it challenging to identify the exact contribution of ordered structures to the improved performance. Here, we prepared a family of small-sized intermetallic core/shell Pt3M@Pt (M = Mn or Fe) catalysts with varied ordering degree by a high-temperature sulfur-confined method. We identified a strong correlation between the ordering degree of the intermetallic Pt3M core of the catalysts and their electrocatalytic activity for the methanol oxidation reaction. Density functional theory calculations show that the intermetallic Pt3M core induces a compressive strain on the Pt-skin, which weakens the CO* binding, lowers the free energy change from CO* to COOH*, and therefore promotes electrocatalytic methanol oxidation.

[Nitrification and Bioaugmentation of Biological Treatment System of Sewage Treatment Plant at High Temperature in Summer].

The influence of temperature (30-45℃) and ammonia-nitrogen volume load on the nitrification function and microbial community of activated sludge in an aerobic tank of a sewage treatment plant were investigated under simulated high-temperature stress in the summer. Meanwhile, the bioaugmentation effectiveness of the middle-temperature-enriched nitrifying sludge (with or without acclimation) was evaluated in two biological treatment systems under high-temperature shock. The results showed that the ammonium-nitrogen (NH4+-N) removal efficiency and the nitrifying bacteria content of the aerobic activated sludge at 30-40℃ were above 90% and up to 4.55% and decreased to 40% and 1.97% at 45℃, respectively. To quickly recover the nitrification function of the biological system under high-temperature shock in the summer, the middle-temperature-enriched nitrifying sludge was acclimated at 40℃ for 61 d and achieved (60±5) mg·(L·h)-1 nitrification activity. Then, its bioaugmentation efficiency was compared with that of the middle-temperature-enriched nitrifying sludge. In the bioaugmentation test, 10% of NH4+-N was removed in the reactor inoculated with 5% (volume fraction) of the acclimated nitrifying sludge, while the reactor needed inoculate with 10% (volume fraction) of the middle-temperature-enriched sludge to achieve the same removal efficiency. The results suggested that middle-temperature-enriched nitrifying sludge, after acclimating at 40℃, has a better enhancement effect under a high-temperature shocking load.

Preparation of polyacrylic-acid/palygorskite composite particles via inverse-suspension polymerization for efficient separation of Ce3+ from aqueous solution.

A novel granular composite adsorbent made from palygorskite (PGS) and polyacrylic acid (PAA) (PAA@PGS) was prepared successfully by inverse-suspension polymerization. Acrylic acid (AA) molecules present in the PGS pores form PAA chains passing through the PGS channels after in situ polymerization, and bond to each other through hydrogen bonds. PAA@PGS was characterized by X-ray diffraction (XRD), Thermogravimetric Analysis (TG/TGA), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). Ce3+ was selected as a model to conduct the adsorption experiment, and the adsorption capacity reached 350 mg/g (initial concentration 500 mg/L, pH 6.0, 303.15 K). PAA@PGS performs well in the presence of interfering ions Na+ and has a high adsorption rate for about one hour. Moreover, PAA@PGS shows an excellent reusability, in the five cycle experiments, all the desorption rates are more than 95%, and when the fifth cycle time was completed, the adsorption capacity could still reach 87.20%.