Porous Chitosan-Silica Hybrid Microspheres as a Potential Catalyst

Chitosan/silica hybrids were synthesized and shaped as microspheres, which may or may not present a core/shell structure, depending on the experimental conditions. The core is constituted by a homogeneous hybrid, while the shell is pure silica. The amino groups of the biopolymer are still accessible as active sites for heterogeneous catalysis

New Layered Double Hydroxides/Phospholipid Bilayer Hybrid Material with Strong Potential for Sustained Drug Delivery System

A new supra-organized hybrid material obtained in aqueous medium via anionic exchange of self-assembled unilamellar anionic liposomes with the nitrate ions present in the interlayers of layered double hydroxides (LDH) is fully characterized. This material presents original properties linked to the simultaneous presence of a phospholipid bilayer derived from liposomes, still used as vectors for lipophilic drugs, and LDH, which protects the bilayer and brings about a pH sensitivity. The exchange rate is controlled via the added amount of liposomes. TGA, XRD, and TEM confirm the organization of the entrapped phospholipids as a bilayer. The presence of the latter allows the material to load lipophilic and neutral drugs, which represent the largest fraction of those newly synthesized. Furthermore, in physiological conditions, preliminary tests show a sustained release of phospholipids (1.5% for 7 days and 6% for 14 days), whereas a fluorescent lipophilic drug-mimic reveals the reorganization of the phospholipids into liposomes in the release medium. In the field of biocompatible materials, these new hybrid particles have a strong potential for the storage and sustained release of neutral or lipophilic drugs

Surfactant Behavior of Ionic Liquids Involving a Drug: From Molecular Interactions to Self-Assembly

Aggregates formed in an aqueous medium by three ionic liquids C_<i>n</i>MImIbu made up of 1-alkyl-3-methyl-imidazolium cation (<i>n</i> = 4, 6, 8) and ibuprofenate anion are investigated. Dynamic light scattering (DLS), cryogenic transmission electron microscopy (cryo-TEM), ¹H nuclear magnetic resonance measurements, and atom-scale molecular dynamics simulations are used to shed light on the main interactions governing the formation of the aggregates and their composition. At high concentration, mixed micelles are formed with a composition that depends on the imidazolium alkyl chain length. For the shortest alkyl chain, micelles are mainly composed of ibuprofenate anions with some imidazolium cations intercalated between the anions. Upon increasing the alkyl chain length, the composition of the aggregates gets enriched in imidazolium cations and aggregates of stoichiometric composition are obtained. Attractive interactions between these aggregates led to the formation of larger aggregates. As suggested by molecular simulations, these larger aggregates might constitute the early stage of phase separation. Transitions from micelles to vesicles or ribbons are observed due to dilution effects and changes in the chemical composition of the aggregates. We also show that aggregation can be probed using simple microscopic quantities such as radial distribution functions and average solvation numbers

Synthesis and Characterization of Crystalline Structures Based on Phenylboronate Ligands Bound to Alkaline Earth Cations

We describe the preparation of the first crystalline compounds based on arylboronate ligands PhB(OH)3– coordinated to metal cations: [Ca(PhB(OH)3)2], [Sr(PhB(OH)3)2]·H2O, and [Ba(PhB(OH)3)2]. The calcium and strontium structures were solved using powder and single-crystal X-ray diffraction, respectively. In both cases, the structures are composed of chains of cations connected through phenylboronate ligands, which interact one with each other to form a 2D lamellar structure. The temperature and pH conditions necessary for the formation of phase-pure compounds were investigated: changes in temperature were found to mainly affect the morphology of the crystallites, whereas strong variations in pH were found to affect the formation of pure phases. All three compounds were characterized using a wide range of analytical techniques (TGA, IR, Raman, XRD, and high resolution 1H, 11B, and 13C solid-state NMR), and the different coordination modes of phenylboronate ligands were analyzed. Two different kinds of hydroxyl groups were identified in the structures: those involved in hydrogen bonds, and those that are effectively “free” and not involved in hydrogen bonds of any significant strength. To position precisely the OH protons within the structures, an NMR-crystallography approach was used: the comparison of experimental and calculated NMR parameters (determined using the Gauge Including Projector Augmented Wave method, GIPAW) allowed the most accurate positions to be identified. In the case of the calcium compound, it was found that it is the 43Ca NMR data that are critical to help identify the best model of the structure

Synthesis and Characterization of Crystalline Structures Based on Phenylboronate Ligands Bound to Alkaline Earth Cations

We describe the preparation of the first crystalline compounds based on arylboronate ligands PhB(OH)3– coordinated to metal cations: [Ca(PhB(OH)3)2], [Sr(PhB(OH)3)2]·H2O, and [Ba(PhB(OH)3)2]. The calcium and strontium structures were solved using powder and single-crystal X-ray diffraction, respectively. In both cases, the structures are composed of chains of cations connected through phenylboronate ligands, which interact one with each other to form a 2D lamellar structure. The temperature and pH conditions necessary for the formation of phase-pure compounds were investigated: changes in temperature were found to mainly affect the morphology of the crystallites, whereas strong variations in pH were found to affect the formation of pure phases. All three compounds were characterized using a wide range of analytical techniques (TGA, IR, Raman, XRD, and high resolution 1H, 11B, and 13C solid-state NMR), and the different coordination modes of phenylboronate ligands were analyzed. Two different kinds of hydroxyl groups were identified in the structures: those involved in hydrogen bonds, and those that are effectively “free” and not involved in hydrogen bonds of any significant strength. To position precisely the OH protons within the structures, an NMR-crystallography approach was used: the comparison of experimental and calculated NMR parameters (determined using the Gauge Including Projector Augmented Wave method, GIPAW) allowed the most accurate positions to be identified. In the case of the calcium compound, it was found that it is the 43Ca NMR data that are critical to help identify the best model of the structure

Synthesis and Characterization of Crystalline Structures Based on Phenylboronate Ligands Bound to Alkaline Earth Cations

We describe the preparation of the first crystalline compounds based on arylboronate ligands PhB(OH)3– coordinated to metal cations: [Ca(PhB(OH)3)2], [Sr(PhB(OH)3)2]·H2O, and [Ba(PhB(OH)3)2]. The calcium and strontium structures were solved using powder and single-crystal X-ray diffraction, respectively. In both cases, the structures are composed of chains of cations connected through phenylboronate ligands, which interact one with each other to form a 2D lamellar structure. The temperature and pH conditions necessary for the formation of phase-pure compounds were investigated: changes in temperature were found to mainly affect the morphology of the crystallites, whereas strong variations in pH were found to affect the formation of pure phases. All three compounds were characterized using a wide range of analytical techniques (TGA, IR, Raman, XRD, and high resolution 1H, 11B, and 13C solid-state NMR), and the different coordination modes of phenylboronate ligands were analyzed. Two different kinds of hydroxyl groups were identified in the structures: those involved in hydrogen bonds, and those that are effectively “free” and not involved in hydrogen bonds of any significant strength. To position precisely the OH protons within the structures, an NMR-crystallography approach was used: the comparison of experimental and calculated NMR parameters (determined using the Gauge Including Projector Augmented Wave method, GIPAW) allowed the most accurate positions to be identified. In the case of the calcium compound, it was found that it is the 43Ca NMR data that are critical to help identify the best model of the structure