Didier Le Cerf

Enhancement of the Solubility and Efficacy of Poorly Water-Soluble Drugs by Hydrophobically-Modified Polysaccharide Derivatives

PurposeThis work was intended to develop and evaluate a new polymeric system based on amphiphilic carboxymethylpullulans (CMP49C8 and CMP12C8) that can spontaneously self-assemble in aqueous solutions and efficiently solubilize hydrophobic drugs.MethodsThe self-assembling properties of CMP49C8 and CMP12C8 were characterized by fluorescence spectroscopy and surface tension measurements. The solubilization of benzophenone and docetaxel was assessed from surface tension measurements, UV spectrometry and HPLC assays. The in vitro cytoxicity of CMP49C8 solutions and the docetaxel commercial vehicle (Tween 80®/Ethanol–water) were evaluated in the absence and in the presence of docetaxel.ResultsCompared to CMP12C8, CMP49C8 in aqueous solutions appeared to self-organize into monomolecular aggregates containing hydrophobic nanodomains, and to significantly increase the apparent solubility of benzophenone. Docetaxel solubility could also be improved in the presence of CMP49C8 but to a lower extent due to the surface properties of the drug. Nevertheless, in vitro, the cytotoxicity studies revealed that against cancer cells, the CMP49C8-docetaxel formulation was equipotent to the commercial docetaxel one. Furthermore, in the absence of the drug, CMP49C8 appeared less cytotoxic against macrophages than the Tween® 80/Ethanol–water.ConclusionsCMP49C8 is a good candidate for solubilizing hydrophobic drugs and could be applied to docetaxel formulations.

Adsorption of cellulose derivatives onto montmorillonite: a SEC–MALLS study of molar masses influence

Abstract Adsorption properties of two commercial neutral cellulose derivatives: hydroxyethylcellulose (HEC) and hydrophobically modified hydroxyethylcellulose (HMHEC) onto montmorillonite were investigated in pure water and in salt solution. Regardless of the polymer, the adsorption onto clay is always larger in pure water than in salt solutions. In other respects, adsorption of the associative HMHEC is always slightly enhanced in comparison with its parent HEC. For both polymers, only simple layer type of adsorption is evidenced (Scatchard linearisation). Finally, a SEC–MALLS study conducted with HEC has shown that adsorption on clay occurs preferentially for the lower molar masses. The adsorbed amount of HEC on clay is larger for the lower molar masses.

Optimization extraction of polysaccharide from Tunisian Zizyphus lotus fruit by response surface methodology: Composition and antioxidant activity.

Response surface methodology using a Box-Behnken design was employed to optimize extraction temperature, extraction time and ratio of water to material to obtain a maximum polysaccharide yield with high uronic acid content and antioxidant property from edible Zizyphus lotus fruit. The optimal conditions were: extraction time of 3h 15min, extraction temperature of 91.2°C and water to solid ratio of 39mL/g. Under these conditions, the experimental extraction yield, uronic acid content and 2,2-diphenyl-1-picrylhydrazyl scavenging ability (IC50) were 18.88%, 41.89 and 0.518mg/mL, respectively. Chemical analysis revealed that the extract was composed of 97.92% carbohydrate of which 41.89% is uronic acid. The extracted polysaccharides, with an average molecular weight of 2720kDa, are composed of arabinose, rhamnose, glucose, fructose, galactose and xylose. Moreover, the polysaccharides exhibited a significant reducing power and anti-lipid peroxidation activities.

Depolymerization of polysaccharides from Opuntia ficus indica: Antioxidant and antiglycated activities

The extraction, purification and degradation of polysaccharides from Opuntia ficus indica cladodes, as well as the evaluation of their antioxidant and antiglycated activities in vitro were investigated. The optimization of the extraction showed that extraction by ultrasound at 40 °C presented the best carbohydrates yield. The degradation of the extracted polysaccharides was achieved by free radical depolymerization with H2O2 in the presence of copper(II) acetate for various reaction times. Sugar contents were determined by colorimetric assays. The macromolecular characteristics of the different isolated and degraded carbohydrates were carried by size exclusion chromatography (SEC/MALS/VD/DRI). These experiments showed that all samples are polysaccharides, which are probably pectins and that molecular weight (Mw) has decreased from 6,800,000 to 14,000 g/mol after 3 h of depolymerization without changing the structure. Preliminary antioxidant and antiglycated tests indicated that degraded polysaccharides for 2 and 3 h showed even better antioxidant and antiglycated activities.

Thermo sensitive behavior of cellulose derivatives in dilute aqueous solutions: From macroscopic to mesoscopic scale

Thermal behaviors of thermo sensitive hydroxypropyl cellulose (HPC), methyl cellulose (MC) and methyl hydroxypropyl cellulose (MHPC) solutions have been investigated in dilute regime of concentration (C<C*) by means of optical density (OD), Quasi Elastic Light Scattering (QELS) and Pyrene Fluorescence Spectroscopy (PyFS) measurements. The importance of controlling the rate of a temperature sweep regarding to the kinetic of association has been demonstrated. MHPC copolymer exhibits only one thermal transition at macroscopic scale (OD and QELS) but two distinct thermal transitions have been evidenced at mesoscopic scale (PyFS) suggesting a double association step for each thermo associative group (i.e. hydroxypropyl and methyl). In HPC/MC mixture, HPC undergoes its own thermal transition. The presence of MC leads to a shift of the temperature of HPC precipitation toward higher temperature even in dilute regime.

Multi-responsive carboxymethyl polysaccharide crosslinked hydrogels containing Jeffamine side-chains.

The paper studies the synthesis and characterization of crosslinked carboxymethylpullulan hydrogels containing Jeffamine (Jef) (M-600 and M-2005) [polyoxyalkyleneamines (polyethylene oxide, polypropylene oxide)] units as side chains, linked through amide bonds. These hydrogels present pH sensitive properties due to the presence of anionic functional groups and thermoassociative properties due to the Jeff units. They were characterized through FTIR spectra, swelling behavior in various media, at various pH or temperatures, retention of hydrophobic molecules, to appreciate their pH-sensitive and thermoassociative (multi-responsive) properties. The interaction with biomolecules as proteins: lysozyme, BSA and antioxidants as: lutein and alpha-tocopherol was studied, to estimate some potential application domains of these new synthesized hydrogels.

Association states of multisensitive smart polysaccharide–block-polyetheramine copolymers

The water soluble properties of different copolymers based on pullulan-block-polyetheramine have been deeply studied. The polyetheramine group (PEA) corresponding to a propylene oxyde/ethylene oxyde ratio (PO/EO) of 29/6, is condensed, via amine link, to pullulans with various chain lengths. Different polysaccharide/PEA (PS/PEA) ratio copolymers have been investigated through macroscopic (cloud point, enthalpy) and mesoscopic scale approaches (critical aggregation concentration (CAC), mean number average hydrodynamic diameter (Dh) or aggregation number (Nag)). These systems are both pH and/or thermo-sensitive. Finally, it seems that three states can describe such systems (i) isolated copolymers (unimers) below the CAC, (ii) water soluble aggregates above the CAC and whatever the PS/PEA ratio is due to hydrophobic interactions and (iii) non-soluble aggregates (above the critical temperature) due to dehydration of polyetheramine groups but only if PS/PEA ratio is low enough.

Direct Effect of Bevacizumab on Glioblastoma Cell Lines In Vitro

Abstract Bevacizumab is a humanized monoclonal antibody directed against the pro-angiogenic factor vascular and endothelial growth factor-A (VEGF-A) used in the treatment of glioblastomas. Although most patients respond initially to this treatment, studies have shown that glioblastomas eventually recur. Several non-mutually exclusive theories based on the anti-angiogenic effect of bevacizumab have been proposed to explain these mechanisms of resistance. In this report, we studied whether bevacizumab can act directly on malignant glioblastoma cells. We observe changes in the expression profiles of components of the VEGF/VEGF-R pathway and in the response to a VEGF-A stimulus following bevacizumab treatment. In addition, we show that bevacizumab itself acts on glioblastoma cells by activating the Akt and Erks survival signaling pathways. Bevacizumab also enhances proliferation and invasiveness of glioblastoma cells in hyaluronic acid hydrogel. We propose that the paradoxical effect of bevacizumab on glioblastoma cells could be due to changes in the VEGF-A-dependent autocrine loop as well as in the intracellular survival pathways, leading to the enhancement of tumor aggressiveness. Investigation of how bevacizumab interacts with glioblastoma cells and the resulting downstream signaling pathways will help targeting populations of resistant glioblastoma cells.

Survival of cord blood haematopoietic stem cells in a hyaluronan hydrogel for ex vivo biomimicry

Haematopoietic stem cells (HSCs) and haematopoietic progenitor cells (HPCs) grow in a specified niche in close association with the microenvironment, the so‐called ‘haematopoietic niche’. Scaffolds have been introduced to overcome the liquid culture limitations, mimicking the presence of the extracellular matrix (ECM). In the present study the hyaluronic acid scaffold, already developed in the laboratory, has been used for the first time to maintain long‐term cultures of CD34+ haematopoietic cells obtained from human cord blood. One parameter investigated was the impact on ex vivo survival of CD34+ cord blood cells (CBCs) on the hyaluronic acid surface, immobilized with peptides containing the RGD motif. This peptide was conjugated by coating the hyaluronan hydrogel and cultured in serum‐free liquid phase complemented with stem cell factor (SCF), a commonly indispensable cytokine for haematopoiesis. Our work demonstrated that these hyaluronan hydrogels were superior to traditional liquid cultures by maintaining and expanding the HPCs without the need for additional cytokines, and a colonization of 280‐fold increment in the hydrogel compared with liquid culture after 28 days of ex vivo expansion. Copyright

Formation of polyelectrolyte complexes with diethylaminoethyl dextran: Charge ratio and molar mass effect

The formation of polyelectrolyte complexes (PECs) between carboxymethyl pullulan and DEAE Dextran, was investigated, in dilute solution, with emphasis on the effect of charge density (molar ratio or pH) and molar masses. Electrophoretic mobility measurements have evidenced that insoluble PECs (neutral electrophoretic mobility) occurs for charge ratio between 0.6 (excess of polycation) and 1 (stoichiometry usual value) according to the pH. This atypical result is explained by the inaccessibility of some permanent cationic charge when screened by pH dependant cationic ones (due to the Hoffman alkylation). Isothermal titration calorimetry (ITC) indicates an endothermic formation of PEC with a binding constant around 10(5) L mol(-1). Finally asymmetrical flow field flow fractionation coupled on line with static multi angle light scattering (AF4/MALS) evidences soluble PECs with very large average molar masses and size around 100 nm, in agreement with scrambled eggs multi-association between various polyelectrolyte chains.