Flame In Situ Synthesis of Metal-Anchored CuO Nanowires for CO Catalytic Oxidation and Kinetic Analysis

Flame in situ synthesis is regarded as a facile technique to fabricate one-dimensional (1D) nanomaterials with the advantages of simple operation, shorter duration, and scale production. This work reports the flame synthesis of transition metal (Ce,Fe)-anchored CuO nanowires on a copper substrate for CO catalytic oxidation. Thermal compressive stresses encourage the CuO nanowires to grow vertically along the grain boundaries, and the metal oxides are nucleated and embedded along the nanowires due to pyrolysis. We examined the catalytic performance of the as-grown catalysts toward CO oxidation, and the results showed that the CeFe-Cu catalyst exhibits outstanding activity near full conversion at 180 °C. With a reaction rate per unit mass of 1.38 mol gcat–1 s–1 and activation energy of 43.54 kJ mol–1, the high activity of the CeFe-Cu catalyst benefits from the synergistic effects of Ce-Fe incorporation. Furthermore, the CeFe-Cu catalyst displays stable cycling performance over five runs and excellent stability in isothermal long-term catalysis tests at 140 °C. Kinetic analysis gives the rate equations for CO oxidation over the Ce-Cu, Fe-Cu, and CeFe-Cu catalysts and reveals the influential role of chemisorbed CO and lattice oxygen in the reaction. The catalytic oxidation of CO undergoes two reduction–oxidation steps as corroborated by the Mars Van Krevelen (MVK) model, and oxygen vacancies are crucial to facilitating the deep oxidation of CO, as confirmed by XPS. Meanwhile, combined with in situ Raman analysis, a reasonable mechanism is proposed. This work provides a fast method of designing 1D hybrid nanostructures for the abatement of carbon monoxide from exhaust gas emissions

NA-MNT and ELISA-MNT intra-assay variation (n = 8).

NA-MNT and ELISA-MNT intra-assay variation (n = 8).</p

Correlations between the HI assay, ELISA-MNT, and NA-MNT for the measurements of anti-H5N1 antibodies.

Antibodies were measured in 40 serum samples from healthy volunteers immunized with two doses of inactivated H5N1 influenza vaccine and compared between the (A) HI assay and ELISA-MNT (B) NA-MNT and HI assay, and (C) NA-MNT and ELISA-MNT. Linear regression equations and correlation coefficients were calculated by linear regression analysis of the log transformed data.</p

Serology results from 40 healthy volunteers received two doses of inactivated H5N1 influenza vaccine.

Serology results from 40 healthy volunteers received two doses of inactivated H5N1 influenza vaccine.</p

Comparison of NA activity between cell lysates and supernatants.

(A) NA activity in cell lysates and supernatants at different time points following infection. Cells were infected with NIBRG-14 (H5N1) virus at a multiplicity of infection of 0.001. Each data point represents the mean of three separate experiments. (B) NA activity in cell lysates and supernatants with different viral inocula. MDCK cells were infected with different dilutions of NIBRG-14, with NA activity measured in either the cell culture supernatant or cell lysates 20 h after inoculation. The total NA activity in the supernatants was calculated and compared with the activity in the cell lysates. (C) The neutralizing antibody titers of serum samples measured by the NA-MNT. The neutralizing antibody titer of NIBSC reference sheep antisera (shRef H5N1), high (huHiPos) and moderate (HuMoPos) seropositive samples, and negative (huNeg) human sera were determined by NA-MNT using either cell supernatants or lysates. Each test was repeated five times, with the CVs calculated accordingly. Note: HuHiPos, HuMoPos, and huNeg samples were obtained from a clinical study of the H5N1 candidate vaccine.</p

H7N9 antibody responses and correlations among the HI assay, ELISA-MNT, and NA-MNT.

92 serum samples from human subjects immunized with either (A) one dose or (B) two doses of candidate H7N9 influenza vaccine were analyzed using either HI assay, NA-MNT, or ELISA-MNT. The correlations among the titers in the 92 serum samples after immunization with one dose of candidate H7N9 influenza vaccines were measured by (C) HI assay versus NA-MNT or (D) ELISA-MNT versus NA-MNT. The correlations among the titers in the 92 serum samples after immunization with two doses of candidate H7N9 influenza vaccines were measured by (E) HI assay versus NA-MNT or (F) ELISA-MNT versus NA-MNT. Linear regression equations and correlation coefficients were calculated by linear regression analysis of the log transformed data.</p

NA-MNT and ELISA-MNT inter-assay variation (n = 9).

NA-MNT and ELISA-MNT inter-assay variation (n = 9).</p

A neuraminidase activity-based microneutralization assay for evaluating antibody responses to influenza H5 and H7 vaccines

Outbreaks of the highly pathogenic avian influenza H5N1 and H7N9 viruses have spurred an unprecedented research effort to develop antivirals and vaccines against influenza. Standardized methods for vaccine evaluation are critical for facilitating vaccine development. Compared with hemagglutination inhibition assays, mounting evidence suggest that microneutralization tests (MNTs) is a better choice for the evaluation of candidate pandemic influenza vaccines because they measure neutralizing antibody activity in cell cultures and are more sensitive in detecting H5 and H7. Here, we report a MNT measuring neuraminidase activity as the read-out (NA-MNT) for quantitative analysis of neutralizing antibodies against avian influenza viruses. Compared to the conventional microneutralization assay (ELISA-MNT), the NA-MNT is faster with lower intra- and inter-assay variations, while no difference in geometric mean titers was found between these two assays for the evaluation of H5N1 and H7N9 vaccines. These results suggest that NA-MNT is a reliable and high throughput method which could facilitate the development of candidate pandemic influenza vaccine.</div

Effect of low pH treatment on vaccine captured by the synthetic receptor.

<p>Influenza strains included in 2010–2011 vaccine (<b>A</b>) A/California/7/2009(H1N1), (<b>B</b>) A/Victoria/210/2009(H3N2) and (<b>C</b>) B/Brisbane/60/2008(Victoria-like) were incubated at the indicated pH for 1 hour and then neutralized to pH 7.2 prior to measurement by both SRID and R-ELISA using the corresponding rabbit strain-specific antibodies. Each treatment was tested in triplicate/experiment and the experiment was repeated at least thrice. Results are shown as mean with error bars indicating the standard deviation.</p

Spiking and recovery.

<p>Each sample was tested in triplicate. Data are shown as mean +/− SD from two experiments.</p><p>HA concentrations were obtained using strain-specific rabbit antibodies.</p