Carbon Nanotube Supported Molybdenum Carbide as Robust Electrocatalyst for Efficient Hydrogen Evolution Reaction.

Molybdenum carbide is considered to be one of the most competitive catalysts for hydrogen evolution reaction (HER) regarding its high catalytic activity and superior corrosion resistance. But the low electrical conductivity and poor interfacial contact with the current collector greatly inhibit its practical application capability. Herein, carbon nanotube (CNT) supported molybdenum carbide was assembled via electrostatic adsorption combined with complex bonding. The N-doped molybdenum carbide nanocrystals were uniformly anchored on the surfaces of amino CNTs, which depressed the agglomeration of nanoparticles while strengthening the migration of electrons. The optimized catalyst (250-800-2h) showed exceptional electrocatalytic performance towards HER under both acidic and alkaline conditions. Especially in 0.5 M H2SO4 solution, the 250-800-2h catalyst exhibited a low overpotential of 136 mV at a current density of 10 mA/cm2 (η10) with the Tafel slope of 49.9 mV dec-1, and the overpotential only increased 8 mV after 20,000 cycles of stability test. The active corrosive experiment revealed that more exposure to high-activity γ-Mo2N promoted the specific mass activity of Mo, thus, maintaining the catalytic durability of the catalyst.

Identification and Characterization of CD133(pos) Subpopulation Cells From a Human Laryngeal Cancer Cell Line.

BACKGROUND: Recent research indicates that CD133 are expressed in several kinds of stem cells, among which, its high expression in laryngeal carcinoma has caused wide concern. To further explore efficaciously targeting drugs to laryngeal carcinoma stem cells (CSCs), we transplanted a solid tumor from CSCs into abdominal subcutaneous tissue of nude mice, and then compared the biological characteristics of laryngeal solid tumors with or without cisplatin intervention. MATERIAL/METHODS: In this study, the expression of CD133 was detected in the Hep-2 cell line by flow cytometry. By applying magnetic cell sorting (MACS) technology, we reported the results of purifying CD133-positive cells from a Hep-2 cell line. Cell proliferation, colony formation, and tumor-forming ability were examined in vitro and in vivo to identify the marker of CSCs in Hep-2 cell line. RESULTS: Upon flow cytometry analysis, CD133 was expressed constantly on 40.12±1.32% in Hep-2 cell line. Cell proliferation and colony formation ability were higher in CD133-positive cells compared to CD133-negative cells, and the in vivo tumorigenesis experiment showed the same results as in vitro assay. The 2 subpopulations cells were both sensitive to DDP, among which, the effect of DPP on proliferation ability and tumor-forming ability of CD133-positive cells was obviously greater than that of CD133-negative cells. CONCLUSIONS: Above all, our study revealed that CD133-positive cells have properties of higher proliferation, colony formation, and tumorigenesis in Hep-2 cell line, indicating that CD133 could be a marker to characterize laryngeal cancer stem cells.

Determination of nitrite in water samples using atmospheric pressure glow discharge microplasma emission and chemical vapor generation of NO species.

In this work, a low-power (<25 W), portable direct current (dc) atmospheric pressure glow discharge microplasma (4 mm × 10  mm) molecular emission spectrometer (APGD-MES) is developed for the determination of nitrite by using chemical vapor generation. Nitrite is on-line reduced to volatile nitric oxide (NO) by 1.5% (m/v) ascorbic acid and 1.0 mol L-1 hydrochloric acid. Then, the generated NO was separated and transferred into the APGD microplasma by an argon stream (100 mL min-1) for its excitation, and NO emission was measured by a microspectrometer. The effects of operational parameters of the APGD microplasma source and vapor generation of nitrite were investigated and the analytical figures of merit for nitrite detection was evaluated. The limit of detection of the proposed method was calculated to be 0.26 µg mL-1 of nitrite by measuring NO emission at 237.0 nm. The calibration curve is linear for the nitrite concentration in the range of 2.0-100.0 µg mL-1 and good precision (2.3%, RSD) is readily achieved for 5.0 µg mL-1 nitrite. The accuracy of this procedure was demonstrated by nitrite detection in a certified reference material. Analyte recoveries test were also performed to verify the accuracy of the method for nitrite determination in a series of environmental water samples. It was found that the concentration of nitrite of these samples were all below the LOD, and the obtained recoveries were in the range of 95-117%. The proposed APGD-MES method provides an alternative useful technique for screening potential nitrite pollution of potable waters.

[Enrichment of triphenyltin in water samples by beta-cyclodextrin cross-linking polymer and determination by hydride-generation atomic fluorescence spectrometry].

A new method was proposed for the enrichment of triphenyltin in water samples by beta-cyclodextrin cross-linking polymer and the quantitative determination of tin in triphenyltin by hydride-generation atomic fluorescence spectrometry. The chemical conditions and instrumental conditions were investigated and optimized. The method is sensitive and precise. The detection limit is 0.1 ng x mL(-1) and the RSD 2.64% (for 0.04 microg x mL(-1)). The proposed method has been successfully applied to the determination of triphenyltin in various water samples.

[Determination of Cd in sediment samples by flow injection on-line anion exchange combined with vapour generation-atomic fluorescence spectrometry].

In the present work, a method was developed for the determination of ultra-trace levels of Cd in sediment samples by atomic fluorescence spectrometry (AFS). A flow injection on-line separation and preconcentration technique coupled with an intermittent injection vapor generation technique was employed in the study. The instrument operating parameters and chemical conditions were optimized. In a 2.0 mol x L(-1) HCl solution, Cd (II) was adsorbed on 717-strong alkaline anion exchange resin, while Cu (II) and Pb (II) passed throngh. Then Cd (II) was eluted by 0.5 mol x L(-1) HNO3. The eluting solution was determined directly by intermittent injection vapor generation atomic fluorescence spectrometry. It was showed that Cd (II) can be preconcentrated effectively and the interference can be completely eliminated by this improved method. The Cd atomic vapor generation efficiency could be greatly enhanced in the presence of Co (II) and 1, 10-phenanthroline. The linear range of the determination was 0-12 microg x L(-1) with a detection limit of 0.058 microg x L(-1). The RSD (5 microg x L(-1), n=7) was 1.09%. The method was convenient, rapid and successfully validated by using national water sediment standard reference materials.

Suppression of lymphangiogenesis in human lymphatic endothelial cells by simultaneously blocking VEGF-C and VEGF-D/VEGFR-3 with norcantharidin.

Lymph node metastasis of tumors is a crucial early step in the metastatic process. Tumor lymphangiogenesis plays an important role in promoting tumor metastasis to regional lymph nodes. Norcantharidin (NCTD) has been reported to possess potent anti-angiogenesis and antitumor properties in several cell lines and xenograft tumor models. However, its role in tumor-associated lymphangiogenesis and lymphatic metastasis remains unclear. Here, we investigated the effect of NCTD on proliferation, apoptosis, migration, invasion and the lymphatic tube formation, lymphangiogenesis, of human lymphatic endothelial cells (HLECs) in vitro by MTT, proliferation assay, Hoechst staining and flow cytometry, scraping line method, Matrigel invasion assay, inverted or fluorescence microscope and transmission electron microscope. Moreover, the underlying mechanisms, such as VEGF-C, VEGF-D, VEGFR-3 at protein and mRNA levels in lymphangiogenesis using 3-dimensional (3-D) culture of HLECs were measured by immunohistochemistry, western blotting and real-time polymerase chain reaction (RT-PCR). It was shown that NCTD inhibited proliferation, migration, invasion and lymphatic tube formation (forming-lymphatic and/or formed-lymphatic) of HLECs, induced HLEC apoptosis (all P<0.01) significantly, in a dose- and time-dependent manner (IC50 6.8 µg/ml); and downregulated the expression of VEGF-C, VEGF-D and VEGFR-3 at protein or/and mRNA levels (P<0.01) in HLEC lymphatic tube formation. Thus, we identified for the first time that NCTD inhibited HLEC lymphangiogenesis by simultaneously blocking VEGF-C and VEGF-D/VEGFR-3 in vitro. The present findings may be of importance to explore the therapeutical target or strategy of NCTD for tumor lymphangiogenesis and lymphatic metastasis.