Synthesis and characterization of a small library of bisglucosides: Influence of the nature of the diol/diphenol used in O-glucosylation.

In this paper, the synthesis of different bisglucosides is investigated through the reaction of two acetylated glucose units with a diol (or diphenol) in order to develop a versatile molecular platform for the future development of bio-based polymers. A panel of five diols and one diphenol is initially used in order to examine the influence of their chemical skeleton on the reaction yield and both nature and proportion of formed species. Reaction products are identified using 1H and 13C NMR spectroscopies completed by MALDI-TOF MS technique. The nucleophilicity of these dihydroxy compounds is identified as being the main factor that governs the reaction characteristics. In particular, the best selectivity is obtained with the use of hydroquinone. Inversely, by-products (oligomers, deacetylated compounds) are observed with the diols defined by higher nucleophilicity despite the choice of stereoselective pathway using acyl protecting groups.

Original synthesis and spectroscopic study of thiophene triazine derivatives with enhanced luminescence properties.

A straightforward access to π-conjugated oligothiophenes bearing amino-rich groups was developed. Palladium-catalyzed C-H arylation applied in the main step of the synthesis allowed to couple 2-thiophenecarbonitriles and aryl bromides with moderate to excellent yields (35-93%). Then, to improve their basic fluorescence properties, these compounds were transformed into their 2,4-diamino-1,3,5-triazine derivatives, also with good to excellent yields (74-98%). UV-Visible absorption and fluorescence studies identified a strongly emissive molecule (fluorescence quantum yield: ΦF = 0.78 ±â€¯0.05), which could find use in sensors for applications in biology and in material chemistry. We observed an antagonistic effect in the spectroscopic properties of oligothiophenes bearing 2,4-diamino-1,3,5-triazine, resulting in improved absorptive and emissive properties for more constrained structures having shorter oligothiophenes chains.

Low doses of bioherbicide favour prion aggregation and propagation in vivo.

Public concerns over the use of synthetic pesticides are growing since many studies have shown their impact on human health. A new environmental movement in occidental countries promoting an organic agriculture favours the rebirth of botanical pesticides. These products confer an effective alternative to chemical pesticides such as glyphosate. Among the biopesticides, the α-terthienyls found in the roots of Tagetes species, are powerful broad-spectrum pesticides. We found that an α-terthienyl analogue with herbicidal properties, called A6, triggers resistant SDS oligomers of the pathogenic prion protein PrPSc (rSDS-PrPSc) in cells. Our main question is to determine if we can induce those rSDS-PrPSc oligomers in vitro and in vivo, and their impact on prion aggregation and propagation. Using wild-type mice challenged with prions, we showed that A6 accelerates or slows down prion disease depending on the concentration used. At 5 mg/kg, A6 is worsening the pathology with a faster accumulation of PrPSc, reminiscent to soluble toxic rSDS-PrPSc oligomers. In contrast, at 10 and 20 mg/kg of A6, prion disease occurred later, with less PrPSc deposits and with rSDS-PrPSc oligomers in the brain reminiscent to non-toxic aggregates. Our results are bringing new openings regarding the impact of biopesticides in prion and prion-like diseases.

Composition, texture and methane potential of cellulosic residues from Lewis acids organosolv pulping of wheat straw.

Cellulosic pulps have been successfully isolated from wheat straw through a Lewis acids organosolv treatment. The use of Lewis acids with different hardness produced pulps with different delignification degrees. The cellulosic residue was characterised by chemical composition, X-ray diffraction, FT-IR spectroscopy, N2 physisorption, scanning electron microscopy and potential for anaerobic digestibility. Surface area and pore volume increased with the hardness of the Lewis acid, in correspondence with the decrease of the amount of lignin and hemicellulose in the pulp. The non linearity of the correlation between porosity and composition suggests that an agglomeration of cellulose fibrils occurs in the early stages of pulping. All organosolv pulps presented a significantly higher methane potential than the parent straw. A methane evolution of 295Ncm(3)/g OM was reached by a moderate improvement of the accessibility of the native straw.

Sorption of Cu(II) Ions on Chitosan-Zeolite X Composites: Impact of Gelling and Drying Conditions.

Chitosan-zeolite Na-X composite beads with open porosity and different zeolite contents were prepared by an encapsulation method. Preparation conditions had to be optimised in order to stabilize the zeolite network during the polysaccharide gelling process. Composites and pure reference components were characterized using X-ray diffraction (XRD); scanning electron microscopy (SEM); N2 adsorption-desorption; and thermogravimetric analysis (TG). Cu(II) sorption was investigated at pH 6. The choice of drying method used for the storage of the adsorbent severely affects the textural properties of the composite and the copper sorption effectiveness. The copper sorption capacity of chitosan hydrogel is about 190 mg·g(-1). More than 70% of this capacity is retained when the polysaccharide is stored as an aerogel after supercrititcal CO2 drying, but nearly 90% of the capacity is lost after evaporative drying to a xerogel. Textural data and Cu(II) sorption data indicate that the properties of the zeolite-polysaccharide composites are not just the sum of the properties of the individual components. Whereas a chitosan coating impairs the accessibility of the microporosity of the zeolite; the presence of the zeolite improves the stability of the dispersion of chitosan upon supercritical drying and increases the affinity of the composites for Cu(II) cations. Chitosan-zeolite aerogels present Cu(II) sorption properties.

A Fluorescent Oligothiophene-Bis-Triazine ligand interacts with PrP fibrils and detects SDS-resistant oligomers in human prion diseases.

BACKGROUND: Prion diseases are characterized by the accumulation in the central nervous system of an abnormally folded isoform of the prion protein, named PrP(Sc). Aggregation of PrP(Sc) into oligomers and fibrils is critically involved in the pathogenesis of prion diseases. Oligomers are supposed to be the key neurotoxic agents in prion disease, so modulation of prion aggregation pathways with small molecules can be a valuable strategy for studying prion pathogenicity and for developing new diagnostic and therapeutic approaches. We previously identified thienyl pyrimidine compounds that induce SDS-resistant PrP(Sc) (rSDS-PrP(Sc)) oligomers in prion-infected samples. RESULTS: Due to the low effective doses of the thienyl pyrimidine hits, we synthesized a quaterthiophene-bis-triazine compound, called MR100 to better evaluate their diagnostic and therapeutic potentials. This molecule exhibits a powerful activity inducing rSDS-PrP(Sc) oligomers at nanomolar concentrations in prion-infected cells. Fluorescence interaction studies of MR100 with mouse PrP fibrils showed substantial modification of the spectrum, and the interaction was confirmed in vitro by production of rSDS-oligomer species upon incubation of MR100 with fibrils in SDS-PAGE gel. We further explored whether MR100 compound has a potential to be used in the diagnosis of prion diseases. Our results showed that: (i) MR100 can detect rSDS-oligomers in prion-infected brain homogenates of various species, including human samples from CJD patients; (ii) A protocol, called "Rapid Centrifugation Assay" (RCA), was developed based on MR100 property of inducing rSDS-PrP(Sc) oligomers only in prion-infected samples, and avoiding the protease digestion step. RCA allows the detection of both PK-sensitive and PK-resistant PrP(Sc) species in rodents samples but also from patients with different CJD forms (sporadic and new variant); (iii) A correlation could be established between the amount of rSDS-PrP(Sc) oligomers revealed by MR100 and the duration of the symptomatic phase of the disease in CJD patients; and (iv) Bioassay experiments showed that MR100 can trap prion infectivity more efficiently than P30 drug. CONCLUSIONS: MR100 is a powerful tool not only for studying the prion aggregation pathways regarding oligomeric and sPrP(Sc) species, but also for developing alternative methods for the detection of prion-infected samples. Considering our bioassay results, MR100 is a promising molecule for the development of prion decontamination approaches.

Optimized Synthesis According to One-Step Process of a Biobased Thermoplastic Polyacetal Derived from Isosorbide.

This paper describes both the synthesis and characterization of a biobased and non-aromatic polyacetal produced from the reaction between isosorbide and methylene chloride. The reaction was conducted in an aprotic dipolar and harmless solvent using a one-step, fast and economical procedure. The chemical composition of this polymer was investigated using Nuclear Magnetic Resonance and Fourier Transform Infra-Red spectroscopies. The molecular weights were examined by size exclusion chromatography and MALDI-TOF spectrometry. The synthesis conditions (concentration, mixing speed, solvent nature, stoichiometry, addition mode of one reactan) were found to strongly influence both polymer architecture and reaction yield. Under moderated stirring conditions, the polyacetal was characterized by a larger amount of macro-cycles. Inversely, under higher intensity mixing and with an excess of methylene chloride, it was mainly composed of linear chains. In this latter case, the polymeric material presented an amorphous morphology with a glass transition temperature (Tg) close to 55 °C. Its degradation temperature was evaluated to be close to 215 °C using thermogravimetry according to multi-ramp methodology. The chemical approach and the physicochemical properties are valuable in comparison with that characteristic of other isosorbide-based polyacetals.

Influence of both cation and alginate nature on the rheological behavior of transition metal alginate gels.

The rheological properties of several ionotropic alginate hydrogels were investigated according to the nature of the divalent cation (Mn(2+), Co(2+), Cu(2+)) and the guluronic fraction of the alginate (HG and LG for "high G-content" and "low G-content"). Six hydrogels (Mn-LG, Mn-HG, Co-LG, Co-HG, Cu-LG and Cu-HG) were synthesized and studied by spectromechanical analyses. On one hand, Cu-HG, Cu-LG and Co-HG behaved as viscoelastic solids: the elastic contribution was higher than the dissipative component in all the frequency range studied (G'>G"). No flow zone (G">G') was detected even at very low values of the shearing frequency. On the other, Mn-HG, Mn-LG and Co-LG presented a spectromechanical behavior that resembled that observed classically for entangled polymers. Indeed, at high frequency, these latter materials could be compared to a viscoelastic solid but at low frequency, the flow zone was described and the viscous character became prevalent with finite relaxation time. Very good correlations with the microscopic structurations of the network were evidenced (rubbery vs. flow zone and fibrillar vs. complex morphology respectively).

Structure of alginate gels: interaction of diuronate units with divalent cations from density functional calculations.

The complexation of (1→4) linked α-L-guluronate (G) and ß-D-mannuronate (M) disaccharides with Mg(2+), Ca(2+), Sr(2+), Mn(2+), Co(2+), Cu(2+), and Zn(2+) cations have been studied with quantum chemical density functional theory (DFT)-based method. A large number of possible cation-diuronate complexes, with one and two GG or MM disaccharide units and with or without water molecules in the inner coordination shells have been considered. The computed bond distances, cation interaction energies, and molecular orbital composition analysis revealed that the complexation of the transition metal (TM) ions to the disaccharides occurs via the formation of strong coordination-covalent bonds. On the contrary, the alkaline earth cations form ionic bonds with the uronates. The unidentate binding is found to be the most favored one in the TM hydrated and water-free complexes. By removing water molecules, the bidentate chelating binding also occurs, although it is found to be energetically less favored by 1 to 1.5 eV than the unidentate one. A good correlation is obtained between the alginate affinity trend toward TM cations and the interaction energies of the TM cations in all studied complexes, which suggests that the alginate affinities are strongly related to the chemical interaction strength of TM cations-uronate complexes. The trend of the interaction energies of the alkaline earth cations in the ionic complexes is opposite to the alginate affinity order. The binding strength is thus not a limiting factor in the alginate gelation in the presence of alkaline earth cations at variance with the TM cations.

New solid lipid microparticles for controlled ibuprofen release: formulation and characterization study.

A hot melt dispersion method was used to prepare new sustained release ibuprofen composite microparticles of a solid lipid at ambient temperature, cetyl alcohol. The dispersion of colloidal silicon dioxide nanoparticles (hydrophilic Aerosil 200 or hydrophobic Aerosil R974) either in the oily phase or in the aqueous phase led to the preparation of large (about 400 µm diameter) surfactant free free-flowing particles. Mapping-scanning electronic microscopy using silicon probe revealed that silicon was in the oily core in all cases. The nature of silica nanoparticles and the way used for their dispersion influenced the internal structure of the composite microparticles and the aggregation of nanoparticles in the core of the microparticles. Hydrophobic Aerosil R974 allowed the formation of homogeneous microparticles. Although silica nanoparticles had no influence on thermic profile, crystalline state of ibuprofen and lipid, they had an influence on the kinetics drug release related to the increase of the size of the composite solid lipid microparticles prepared.

Structural regime identification in ionotropic alginate gels: influence of the cation nature and alginate structure.

The morphologies of several ionotropic alginate hydrogels and aerogels were investigated by SAXS according to the nature of the divalent metal cation (Mn(2+), Co(2+), Zn(2+), Cu(2+)) and the guluronic fraction of the alginate. All alginate hydrogel and aerogel samples show isotropic small-angle X-ray scattering. Gelation results from cooperative associations of cations and chain segments and yields different nanostructures, that is, nanofibrillar morphology or multiple junction morphology, according to cation type and eventually mannuronic/guluronic ratio. Therefore, Mn and Cu gels present the same morphology whatever the guluronic ratio, whereas Co and Zn gels yield different nanostructures. In the size range investigated by SAXS (~10-200 Å), the structure of aerogels obtained by CO(2) supercritical drying is found to be inherited from the morphology of the parent hydrogel whatever the initial structural regime.

Marine polysaccharides and their conversion into functional materials.

Natural polysaccharides are supports for sensors, absorbents and catalysts. They are also gelling agents in the aqueous phase, due to the high level of dispersion of hydrocolloids. This article focuses on an effective method to prepare dry materials which retain the dispersion of the polymer hydrogel, namely polysaccharide aerogels. The diverse surface functionalities like hydroxy, carboxy or amino groups of the polysaccharide aerogels are accessible to catalysts and reactants and can be easily modified to tune the functionality of the materials.

Chitosan aerogel: a recyclable, heterogeneous organocatalyst for the asymmetric direct aldol reaction in water.

Aerogel microspheres of chitosan, an abundant biopolymer obtained from marine crustaceans, have been successfully applied to catalyze the asymmetric aldol reaction in water, providing the products in high yields and with good stereoselectivity (up to 93% ee) and recyclability (up to 4 runs). Yields were favourably affected by additives such as DNP and stearic acid.

Synthesis, texture, and photoluminescence of lanthanide-containing chitosan-silica hybrids.

Three different types of photoluminescent hybrid materials containing trivalent lanthanide (Ln(3+) = Eu(3+), Tb(3+)) ions, chitosan, and silica have been prepared with different structural features. The different silica sources lead to diverse microstructures of hybrid materials, with silica being homogeneously dispersed in the chitosan materials (LnChS-H), or forming a core-shell morphology. Postsynthesis treatment is necessary for embedding the luminescent probe. The Ln(3+)-based materials have been investigated by photoluminescence spectroscopy (12-300 K). The chitosan-Eu(3+)-related local environment is maintained in the EuChS-H hybrid material. The emission features of the core-shell materials are characterized by the presence of two Eu(3+) distinct local environments, one associated with the chitosan core and the other with the silica shell.

Nanostructure of calcium alginate aerogels obtained from multistep solvent exchange route.

Ca-alginate materials were studied by small-angle X-ray scattering (SAXS) at different steps of conversion from gel to aerogel in order to determine the relation between the polymer organization at the nanoscale in the gels and the final dry aerogel. In all cases, i.e. before and after the different exchanges of solvents and after the formation of the aerogel, the SAXS patterns exhibit an asymptotic behavior at low q values (in the experimental q range 7x10(-3) up to 2.10(-2) A(-1)) close to I(q) approximately q(-1), indicative of randomly oriented rod-like scattering objects. The evolution of the diameter of such rod-like objects was thus deduced from the maxima observed on Kratky plots, i.e. I(q) q2 vs q. The results are in perfect agreement qualitatively (rod-like anisometry type of the scattering objects) and quantitatively (diameter of the rods) with direct SEM observations of the morphology of aerogels and with the results of N2 adsorption on the aerogel. This is evidence that in the chosen experimental processing conditions, the morphology of the aerogel depends on the morphology of pre-existing objects within the gel, i.e. that the structure of the aerogel provides a correct image of the structure of the parent gel.

Photoluminescent porous alginate hybrid materials containing lanthanide ions.

The photoluminescence features of Eu(3+)-, Tb(3+)-, Tb(3+)/Eu(3+)-alginate aerogel (hydrogel and alcogel) and Eu(3+)-alginate xerogel hybrids were investigated. The Eu(3+)-alginate aerogel and alcogel exhibit the highest (5)D0 quantum efficiencies (9.9 and 8.2%, respectively), while the hydrogel and xerogel have lower values (5.2 and 5.6%, respectively). The Tb(3+)/Eu(3+) hybrids are multiwavelength emitters in which the emission color can be tuned across the chromaticity diagram from the red toward the yellowish-green spectral regions, crossing the white area by selecting the excitation wavelength.

Electroactive nanorods and nanorings designed by supramolecular association of pi-conjugated oligomers.

In investigations into the design and isolation of semiconducting nano-objects, the synthesis of a new bisureido pi-conjugated organogelator has been achieved. This oligo(phenylenethienylene) derivative was found to be capable of forming one-dimensional supramolecular assemblies, leading to the gelation of several solvents. Its self-assembling properties have been studied with different techniques (AFM, EFM, etc.). Nano-objects have successfully been fabricated from the pristine organogel under appropriate dilution conditions. In particular, nanorods and nanorings composed of the electroactive organogelator have been isolated and characterized. With additional support from an electrochemical study of the organogelator in solution, it has been demonstrated by the EFM technique that such nano-objects were capable of exhibiting charge transport properties, a requirement in the fabrication of nanoscale optoelectronic devices. It was observed that positive charges can be injected and delocalized all along an individual nano-object (nanorod and nanoring) over micrometers and, remarkably, that no charge was stored in the center of the nanoring. It was also observed that topographic constructions in the nanostructures prevent transport and delocalization. The same experiments were performed with a negative bias (i.e., electron injection), but no charge delocalization was observed. These results could be correlated with the nature of 1, which is a good electron-donor, so it can easily be oxidized, but can be reduced only with difficulty.

Self-organized ureido substituted diacetylenic organogel. Photopolymerization of one-dimensional supramolecular assemblies to give conjugated nanofibers.

The introduction of the urea function as structure directing agent of diacetylene organogels (DA-OGs) has been achieved. Despite the urea function being one of the most frequently used structure directing agents for the formation of organogels, it has never been exploited in the fabrication and photopolymerization of DA-OGs. The self-association of ureas involving two hydrogen bonds is much stronger than that of urethanes or amides, and the resulting supramolecular assemblies are completely insoluble. In this context, 1,1'-(hexa-2,4-diyne-1,6-diyl)bis(3-(10-(triethoxysilyl)decyl)urea) 2 was synthesized. Compound 2 was soluble owing to the triethoxysilane function that we recently used in the fabrication of a silylated bis-urea-stilbene organogel. It formed an organogel, and its photopolymerization was studied in cyclohexane. The loss of the gel state and the formation of a red solution resulting from the polymerization were found to be the result of the constraints introduced by the urea function in close vicinity to the polymerizable function. To obtain an ureido substituted diacetylenic organogelator affording a blue highly conjugated polydiacetylene (PDA) without a sol-gel transition, a propylene spacer was introduced to move the urea function away from the polymerizable function (derivative 3). The thermochromism exhibited by the latter in the solid state was studied. Using the same setup and the same sample, UV-vis and FTIR spectra were simultaneously recorded as a function of the temperature to highlight a relation between color changes and urea association mode changes. The data showed that the reversible thermochromic transition must be associated with a reversible supramolecular modification and, conversely, that irreversible chromic transitions are the result of irreversible structural modifications. The chromic effects of the acidic hydrolysis-polycondensation of the trialkoxysilyl groups to form a siloxane network were studied on a thin film of 3. In the same way, solvent effects on the color of the organogels of 3 were also investigated. Correlations could be established between the different stimuli. These results provide a deeper understanding of the precise molecular mechanism of the blue to red transition and of the reversibility of the purple to red transition generally encountered in PDA thermochromism.