A fully bio-sourced adsorbent of heavy metals in water fabricated by immobilization of quinine on cellulose paper

International audienceThe fabrication of a fully bio-sourced adsorbent of Cd(II) by covalent immobilization of quinine on cellulose paper is described. The double bond of commercially available quinine was converted to a terminal alkyne function which was reacted with cellulose paper, chemically modified with azide functions, through a 1,3-dipolar cycloaddition, leading to Cell-Quin. The adsorption efficiency of Cell-Quin was investigated to determine the optimal pH, contact time and dose of adsorbent, ultimately leading to high levels of removal. The mechanism of adsorption of Cell-Quin was deeply rationalized through kinetic experiments and isotherm modeling. We also showed that Cell-Quin could adsorb other heavy metals such as Cu(II), Pb(II), Ni(II) and Zn (II)

Motifs Covalents Hydrophobes Sur du Papier de Cellulose par Ligations de type Photothiol-X

International audienceIn the current study, we introduce photothiol-X chemistry as a powerful method to create hydrophobic patterns covalently grafted to the surface of cellulose paper. The general strategy builds on the use of a cellulose-based molecular printboard featuring disulfide functions which upon spatiocontrolled light irradiation at 365 nm allows robust photothiol-X ligations with hydrophobic moieties. A screening of structurally diverse molecular architectures as hydrophobic coating was conducted, and the most impressive result obtained with cholesterol moieties allows the creation of spatially well-resolved hydrophobic patterns with a contact angle of 140.8°. Our discoveries are supported by in-depth characterization studies using Fourier transform infrared spectroscopy, X-ray photoelectron spectrometry, and scanning electron microscopy analyses

Biodiesel production from palm oil using sulfonated graphene catalyst

International audienceIn this study we report on sulfonated graphene, obtained by chemical exfoliation of inexpensive graphite and functionalization of the resulting graphene sheets with benzene sulfonic acid, as a new active catalyst for the transesterification of palm oil with methanol into biodiesel. The experimental conditions for obtaining fatty acid methyl esters were carefully optimized through the evaluation of several parameters including the catalyst loading, temperature, reaction time and methanol-to-oil molar ratio. Of particular relevance, we noticed that an excess of methanol was required to allow high transesterification yield, but an excessive dilution proved to be deleterious for the reaction yield due to lower interactions between the reactants and the catalyst. The heterogeneous catalyst showed a high thermal robustness and was successfully recycled without significant erosion of the reaction yield. Our catalytic system yields biodiesel with a high purity (>98%) after a single filtration and do not produce aqueous waste. (C) 2017 Elsevier Ltd. All rights reserved

Cellulose paper azide as a molecular platform for versatile click ligations: application to the preparation of hydrophobic paper surface

International audienceA cellulose paper sheet, chemically modified with azide functions, is described to be a versatile molecular platform for copper-catalyzed 1,3-dipolar cycloaddition with terminal alkynes. This 3-step methodology was carefully optimized at each stage of the process with the support of experimental and physical evidences. Our approach allows the surface coverage of structurally diverse molecular architectures through a covalent grafting with non-hydrolysable chemical linkers. This robust linkage is highlighted with the surface hydrophobization of cellulose paper through the click ligation of cholesterol units as renewable and inexpensive hydrophobic agents. The resulting water-resistant and water-repellent paper-based material shows powerful oleophilicity properties and displays a high contact angle of 139.6°

Graphene-catalyzed transacetalization under acid-free conditions

International audience1,2- and 1,3-Diols are readily protected as cyclic acetals and ketals through a graphene-catalyzed transacetalization process. The methodology features an atom economic procedure since quasi-stoichiometric conditions have been developed. Unlike prior systems, the graphene-catalyzed transacetalization is performed under Bronsted and Lewis acid-free conditions and without solvent. Our method has been applied to several volatile compounds that are unsuitable for complex work-up and extensive purification steps. The very unusual catalytic properties of graphene for transacetalization reactions are ascribed to molecular charge transfer between graphene and substrates. (C) 2016 Elsevier Ltd. All rights reserved

Cellulose paper grafted with polyamines as powerful adsorbent for heavy metals

International audienceThe preparation of new adsorbents for heavy metals consisting of cellulose paper grafted with polyamine moieties is described. The tosylation of pristine cellulose paper allowed the subsequent displacement of the tosylated leaving groups with either ethylenediamine or spermine provided the corresponding cellulose-based polyaminated adsorbents Cell-Ed and Cell-Sperm, respectively. Optimizations related to the influence of experimental conditions (time and pH) on the adsorption processes associated to detailed studies devoted to the understanding of the mechanism of adsorption through kinetic experiments and isotherm modeling provided a rational understanding for the removal Cu(II) and Pb(II). Interestingly, Cell-Sperm also displayed outstanding adsorption properties for other metal cations such as Cd(II), Zn(II) and Fe(II). [GRAPHICS]

Cellulose fonctionnalisée par un heptil-mannose: un nouvel outil thérapeutique et diagnostic ciblant les Escherichia coli adhérents et invasifs

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Cellulose fonctionnalisée par un heptyl-mannose: un nouvel outil thérapeutique et diagnostic ciblant les Escherichia coli adherents et invasifs

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Heptylmannose-functionalized cellulose for the binding and specific detection of pathogenic E. coli

International audienceWe developed a chemical method to covalently functionalize cellulose nanofibers and cellulose paper with mannoside ligands displaying a strong affinity for the FimH adhesin from pathogenic E. coli strains. Mannose-grafted cellulose proved efficient to selectively bind FimH lectin and discriminate pathogenic E. coli strains from non-pathogenic ones. These modified papers are valuable tools for diagnosing infections promoted by E.coli, such as cystitis or inflammatory bowel diseases, and the concept may be applicable to other life-threatening pathogens. The worldwide spread of antibiotic resistances raises serious health problems, and has driven the identification of new virulence factors and development of alternative antibacterial therapeutics. Mannose-binding FimH adhesin, expressed by Escherichia coli strains has been extensively studied as a target for disrupting bacterial attachment to the host cells. 1 Impressive results were obtained in the context of urinary tract infections (UTI), a prevalent infection type generally mediated by the attachment of uropathogenic E. coli strains (UPEC) to the highly mannosylated uroplakin transmembrane protein of urothelial lining cells. FimH antagonists orally administered to in vivo UTI mouse models, were shown to decrease the E.coli load in the bladder by several orders of magnitude, 2-4 making them competitive with conventional antibiotic treatment. 5,6 This concept was more recently extended to Crohn's disease (CD), an inflammatory disorder of the intestine where an altered gut microbiota, particularly the presence of adherent-invasive E. coli strains (AIEC), is suspected to play a key role in the pathogenesis. 7 Synthetic derivatives of heptylmannoside (HMan), a nanomolar FimH antagonist, 8 were shown to lower the AIEC bacterial level, signs of colitis and gut inflammation when administered per os (10 mg/kg) in CD mouse models. 9,10 Sensitive and rapid diagnostic systems are essential to evaluate the presence of E. coli expressing FimH adhesin in gut microenvironments in order to properly stratify patients before treatment. While the high prevalence of UPEC in the normally sterile urinary tract environment facilitates diagnosis, the AIEC niche is more complex, located at the ileal mucosa in 21 to 63% of CD patients, 11,12 within an ecological community of hundreds of symbiotic microorganisms. Furthermore, no specific biomarkers are currently effective at distinguishing AIEC from other commensal E. coli of the gut microbiota. Previously, it has been shown that AIEC pathobiont possesses specific allelic variants in the fimH gene, conferring them a high ability to adhere in vitro and to colonize the gut of CEABAC10 mice. 13 Establishing an approach to discriminate the strong mannose-binders from other bacteria would therefore be of tremendous importance for efficient diagnosis. In this work, we developed a heterogeneous support to specifically trap and accumulate pathogenic E.coli from biological fluids. Heptyl-α-D-mannoside (HMan) was grafted by click chemistry techniques onto cellulose nanofibers (CN) and cellulose paper (CP). HMan was previously identified as a potent binder of the isolated FimH lectin domain. 8 It should be noted that the lectin domain represents the high-affinity state of FimH under mechanical force and that full-length FimH display a lower affinity for mannosides. 14,15 Covalently functionalized CN or CP were characterized by Fourier transform spectroscopy (FTIR), elemental analysis, X-ray photo-electron spectrometry (XPS), and scanning electron microscopy (SEM). HMan-CN was first compared in vitro against CN grafted with lower FimH affinity ligands i.e. Man-CN lacking the hydrophobic heptyl chain, and HGlc-CN an analog with a glucose sugar that is not recognized by FimH lectin (Scheme 1). In addition, we switched the anomeric oxygen atom to a sulfur and synthesized HSMan-CN to prevent potential sugar hydrolysis from the surface by mannosidases. The modified CN were first assessed for their faculty to bind FimH and to prevent AIEC adhesion to intestinal cells. HMan-CN was then orally administered to the CEABAC10 mouse model of CD to assess its capacity to decrease AIEC in the feces of AIEC-infected mice and to act as a potential CD therapeutic. HM was next coated on CP and the capacity of the HMan-CP to selectively catch AIEC in solution was analyzed. Scheme 1. Chemical synthesis of the sugar-coated cellulose fibers