Absence of association between pyronaridine in vitro responses and polymorphisms in genes involved in quinoline resistance in Plasmodium falciparum

<p>Abstract</p> <p>Background</p> <p>The aim of the present work was to assess the <it>in vitro </it>cross-resistance of pyronaridine with other quinoline drugs, artesunate and several other commonly used anti-malarials and to evaluate whether decreased susceptibility to pyronaridine could be associated with genetic polymorphisms in genes involved in reduced quinoline susceptibility, such as <it>pfcrt</it>, <it>pfmdr1</it>, <it>pfmrp </it>and <it>pfnhe</it>.</p> <p>Methods</p> <p>The <it>in vitro </it>chemosusceptibility profiles of 23 strains of <it>Plasmodium falciparum </it>were analysed by the standard 42-hour ³H-hypoxanthine uptake inhibition method for pyronaridine, artesunate, chloroquine, monodesethylamodiaquine, quinine, mefloquine, lumefantrine, atovaquone, pyrimethamine and doxycycline. Genotypes were assessed for <it>pfcrt</it>, <it>pfmdr1</it>, <it>pfnhe-1 </it>and <it>pfmrp </it>genes.</p> <p>Results</p> <p>The IC₅₀values for pyronaridine ranged from 15 to 49 nM (geometric mean = 23.1 nM). A significant positive correlation was found between responses to pyronaridine and responses to artesunate (<it>r²</it>= 0.20; <it>P </it>= 0.0317) but too low to suggest cross-resistance. No significant correlation was found between pyronaridine IC₅₀and responses to other anti-malarials. Significant associations were not found between pyronaridine IC₅₀and polymorphisms in <it>pfcrt</it>, <it>pfmdr1</it>, <it>pfmrp </it>or <it>pfnhe-1</it>.</p> <p>Conclusion</p> <p>There was an absence of cross-resistance between pyronaridine and quinolines, and the IC₅₀values for pyronaridine were found to be unrelated to mutations in the transport protein genes <it>pfcrt</it>, <it>pfmdr1</it>, <it>pfmrp </it>or <it>pfnhe-1</it>, known to be involved in quinoline resistance. These results confirm the interest and the efficacy of the use of a combination of pyronaridine and artesunate in areas in which parasites are resistant to quinolines.</p

Polyaniline/palladium nanohybrids for moisture and hydrogen detection.

Palladium nanoparticles display fascinating electronic, optical and catalytic properties, thus they can be used for various applications such as sensor fabrication. Conducting polymers such as polyaniline have also been widely used in sensor technology due to its cost effectiveness, versatility, and ease of synthesis. In this research, attention was given to unify the exceptional properties of these two materials and construct palladium nanoparticle coated polyaniline films to detect hydrogen and moisture. Electrochemical polymerization of aniline was carried out on gold sputtered epoxy resin boards. Polyaniline film was generated across a gap of 0.2 mm created by a scratch made on the gold coating prior to electrochemical polymerization. A palladium nanoparticle dispersion was prepared using sonochemical reduction method and coated on to polyaniline film using drop-drying technique. Polyaniline only films were also fabricated for comparative analysis. Sensitivity of films towards humidity and hydrogen was evaluated using impedance spectroscopy in the presence of the respective species. According to the results, polyaniline films exhibited an impedance drop in the presence of humidity and the response was significantly improved once palladium nanoparticles were incorporated. Interestingly, polyaniline only films did not respond to hydrogen. Nevertheless, palladium nanoparticle coated polyaniline films exhibited remarkable response towards hydrogen

Aromatic Reduction Over Supported Modified Platinum Catalysts Influence of a Second Metal on the Sulfur Resistance of Platinum

Pt-M/Al2O3 bimetallic catalysts with M = Ge, Au or Pd were prepared and characterised by H2-O2 volumetric titration and IR(CO) spectroscopy. The effects of the second metal on the sulfur resistance of platinum were investigated by the hydrogenation of orthoxylene. Compared to platinum monometallic reference catalyst, the bimetallic catalysts ranking in terms of hydrogenation activity was PtPd > PtAu = Pt >> PtGe. Correlation between these catalysis results and electronic properties extracted from IR(CO), or orthoxylene hydrogenation without sulfur, shows that sulfur resistance of platinum can not be exclusively related to an electronic effect and an electrodeficient character of Pt surface atoms. The mechanism of sulfur poisoning is discussed

Preparation of bimetallic Pd-Fe / Al

Bimetallic Pd-Fe/Al2O3 catalysts were prepared by underpotential deposition (UPD) of iron on parent Pd/AL2O3 catalysts of varying dispersion. The potential of palladium particles was controlled by the supplementary redox system H+/H2. Iron introduced by this method improves the activity of small palladium particles for the hydrogenation of isoprene in the liquid phase. An explanation of this phenomenon would be a selective deposit of iron on or near the palladium sites of low coordination. However, the promoting effect of iron disappears after exposure of bimetallic catalysts to air and subsequent reduction

Etude in situ par EXAFS de la réaction de reformage sur les systèmes Pt/Al2O3 et PtRe/Al2O3 sulfurés

La technique EXAFS a été utilisée pour suivre in situ dans les conditions de reformage (T=500°C. P(H2) = 8 bars. H2 : n-C7H16 = 1:1 et T=300°C, P(H2 ) = 3 bars H2 : n-C7H16 = 1:1), l'évolution de la structure des deux catalyseurs Pt/Al2O3-Cl et PtRe/Al2O3-Cl sulfurés. On a observé la grande stabilité de la phase métallique du bimetallique comparée à celle du monométallique. La phase métalique de ce dernier subit une agglomération dès la réduction a 500° C , processus qui s'accentue jusqu'à la fin de la réaction de reformage.EXAFS has been used to follow in situ the structural evolution of sulfided Pt/Al2O3-Cl and PtRe/Al2O3-Cl catalysts during the hydrocarbon reaction (T=500°C, P(H2) = 8 bars H2 : n-C7H16 = 1:1 and T=300°C, P(H2) = 3 bars H2 : n-C7H16 = 1:1). The hydrocarbon conversion was monitored, via on line analysis, with a gas chromatograph. For the monometallic, we observe a sintering of the metal particles. In the case of sulfided PtRe/Al2O3-Cl catalysts no sintering of the metallic particles was observed

Interaction between Pt(acac)2 and alumina surfaces studied by XAS

The anchoring and decomposition mechanisms of platinum(II) bis-acetylacetonate on alumina surfaces are studied by X-ray absorption spectroscopy at the platinum LIII edge. A distinction is made between highly reactive surfaces which are partially dehydroxylated and exhibit coordinatively unsaturated surface sites, and deactivated surfaces which are covered by a monolayer of OH groups. The samples are studied after three stages of a wet impregnation synthesis: after drying at room temperature, drying at 120 8C and calcination at 350 8C. The XANES signal and the filtered EXAFS signals of the first and second coordination shells around platinum were analyzed. Two different mechanisms are discussed for the two types of supports

Study of the reaction mechanisms between Sn-(n-C4H9)4 and alumina surface sites. Application to the controlled preparation of PtSn/Al2O3 catalysts

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Improvements in selectivity and stability of Rh catalysts modified by SnBu₄. dehydrogenation of isobutane to isobutene

RhSn/SiO2 bimetallic catalysts prepared via an organometallic route have proved to be very active and selective toward several hydrogenation reactions. In this work these catalysts were studied for the dehydrogenation of isobutane to isobutene. It was found that Rh/SiO2 monometallic catalysts had a null selectivity to isobutene, and this selectivity increased up to more than 90% after the addition of tin, using SnBu4 as precursor.Facultad de Ciencias Exacta