No abstract

International audienceHerein, we report on a three-component supra molecular hybrid system built from specific recognition processes involving a Dawson-type polyoxometalate (POM) ,P2W18O62](6-), a cationic electron-rich cluster [Ta6Br12(H2O)(6)](2+), and gamma-cyclodextrin (gamma-CD). Such materials have been investigated using a bottom-up approach by studying the specific interactions between gamma-CD and both types of inorganic units. Their ability to interact has been investigated in the solid state by single-crystal X-ray diffraction (XRD) and in solution using multinuclear NMR methods (including DOSY, EXSY, and COSY), electrospray ionization mass and UV-vis spectroscopies, electrochemistry, and isothermal titration calorimetry experiments. Single-crystal XRD analysis reveals that POM:gamma-CD constitutes a highly versatile system which gives aggregates with 1:1, 1:2, and 1:3 stoichiometry. Surprisingly, these arrangements exhibit a common feature wherein the gamma-CD moiety interacts with the Dawson-type POMs through its primary face. We present also the first structural model involving an octahedral-type metallic cluster with gamma-CD. XRD study reveals that the cationic [Ta6Br12(H2O)(6)](2+) ion is closely embedded within two gamma-CD units to give a supramolecular ditopic cation, suitable to be used as a linker within extended structure. Solution study demonstrates clearly that pre-associations exist in solution, for which binding constants and thermodynamic parameters have been determined, giving preliminary arguments about the chaotropic nature of the inorganic ions. Finally, both building blocks, i.e., the ditopic supramolecular cation {[Ta6Br12(H2O)(6)]@2CD}(2+) and the Dawson-type anion, react together to give a three-component, well-ordered hybrid material derived either as a supramolecular hydrogel or single crystals. The solid-state structure shows an unprecedented helicoidal tubular chain resulting from the periodic alternation of POM and supramolecular cation, featuring short hydrogen-bonding contacts between the electron-poor POM and electron-rich cluster. The 1D tubular ionic polymer observed in the single crystals should make it possible to understand the long-range ordering observed within the hydrogel hybrid material. The supramolecular chemical complementarities between the gamma-CD-based ditopic cation and POM open a wide scope for the design of hybrid materials that accumulate synergistic functionalities

In this communication, we report on a noteworthy hybrid supramolecular assembly built from three functional components hierarchically organized through noncovalent interactions. The one-pot synthesis procedure leads to the formation of large Mo-blue ring-shaped anion {Mo}, which contains the supramolecular adduct based on the symmetric encapsulation of the Dawson-type [PWO] anion by two γ-cyclodextrin units. Such a nanoscopic onion-like structure, noted [PWO]@2γ-CD@{Mo} has been characterized by single-crystal X-ray diffraction, thus demonstrating the capability of the giant inorganic torus to develop relevant supramolecular chemistry, probing the strong affinity of the inner and outer faces of the γ-CD for the polyoxometalate surfaces. Furthermore, interactions and behavior in solution have been studied by multinuclear NMR spectroscopy, which supports specific interactions between γ-CD and POM units. Finally, the formation of this three-component hybrid assembly from one-pot procedure, in water and using nearly stoichiometric conditions, is discussed in terms of the driving forces orchestrating this highly efficient multilevel recognition process.

Cardiovascular diseases, like atherosclerosis, and neurodegenerative diseases affecting the central nervous system (CNS) are closely linked to alterations of cholesterol metabolism. Therefore, innovative pharmacological approaches aiming at counteracting cholesterol imbalance display promising therapeutic potential. However, these approaches need to take into account the existence of biological barriers such as intestinal and blood-brain barriers which participate in the organ homeostasis and are major defense systems against xenobiotics. Interest in cyclodextrins (CDs) as medicinal agents has increased continuously based on their ability to actively extract lipids from cell membranes and to provide suitable carrier system for drug delivery. Many novel CD derivatives are constantly generated with the objective to improve CD bioavailability, biocompatibility and therapeutic outcomes. Newly designed drug formulation complexes incorporating CDs as drug carriers have demonstrated better efficiency in treating cardiovascular and neurodegenerative diseases. CD-based therapies as cholesterol-sequestrating agent have recently demonstrated promising advances with KLEPTOSE ® CRYSMEB in atherosclerosis as well as with the 2-hydroxypropyl-β-cyclodextrin (HPβCD) in clinical trials for Niemann-Pick type C disease. Based on this success, many investigations evaluating the therapeutical beneficial of CDs in Alzheimer's, Parkinson's and Huntington's diseases are currently on-going.

No abstract

International audienceno abstrac

International audienceno abstrac

Cyclodextrins (CDs) can be envisaged to cure some diseases related to the brain, but the behavior of these compounds toward the blood-brain barrier (BBB) remains largely unexplored to envisage such clinical applications. To fulfill this gap, the toxicity and endothelial permeability for native, methylated, and hydroxypropylated ␣-, ␤-, and ␥-CDs have been studied on an in vitro model of BBB. As shown by the endothelial permeability for sucrose and immunofluorescence stainings, the native CDs are the most toxic CDs (␣-Ͼ ␤-Ͼ ␥-CD). Whereas the chemical modification of ␤-CD did not affect the toxicity of this CD, differences are observed for the ␣-and ␥-CD. To determine the origin of toxicity, lipid effluxes on the brain capillary endothelial cells were performed in the presence of native CDs. It was found that ␣-CD removed phospholipids and that ␤-CD extracted phospholipids and cholesterol. ␥-CD was less lipidselective than the other CDs. Finally, the endothelial permeability of each CD has been determined. Surprisingly, no structure/ permeability relationship has been observed according to the nature and chemical modifications of CDs.Cyclodextrins (CDs) are cyclic oligosaccharides composed of 6, 7, or 8 glucose units named ␣-, ␤-, or ␥-cyclodextrin, respectively. These compounds are widely used in the pharmaceutical field to improve the dissolution rate,