Search results for "dextrin"
showing 10 items of 297 documents
Polyaminocyclodextrin nanosponges: synthesis, characterization and pH-responsive sequestration abilities
2016
New pH-responsive nanosponges were obtained by reacting four different polyaminocyclodextrins with heptakis-(6-bromo)-(6-deoxy)-β-cyclodextrin. The materials obtained were characterized by various techniques (FT-IR, potentiometric titration, differential scanning calorimetry (DSC), porosimetry (BET), 13C{1H} CP-MAS NMR). Their adsorption abilities at different pH values were verified towards a suitable set of model guests, and seem mainly controlled by electrostatic interactions, as a function of the protonation/charge status of the polymer matrix. By contrast, data positively point out a lesser importance assumed by the induced-fit effect, important in affecting the formation of host–guest…
Cyclodextrins in Polymer Synthesis: Influence of Acrylate Side Groups on the Initial Rate of Radical Polymerization of Various Acrylate/Methylated β…
2001
Methylated β-cyclodextrin was used to complex the hydrophobic monomers n-propyl acrylate (1), n-butyl acrylate (2), n-pentyl acrylate (3), n-hexyl acrylate (4), and cyclohexyl acrylate (5) respectively yielding the corresponding water-soluble host/guest-complexes 1a−5a. The complexes were polymerized in water by free radical mechanism and the initial polymerization rates (v0) determined. We found that v0 increases as follows: 1a (12.5), 2a (27.5), 3a (44.2), 5a (49.4), 4a (75.8 × 10-6 mol·L-1·s-1). To investigate the influence of the hydrophobic character of the guest monomers on the reaction rate, the water solubilities of the uncomplexed monomers 1−5 were determined by HPLC measurements.…
Cyclodextrins in polymer synthesis: Influence of methylated β-cyclodextrin as host on the free radical copolymerization reactivity ratios of hydropho…
2001
Methylated (β-cyclodextrin (me-β-CD) was used to complex the hydrophobic monomers n-butyl acrylate (1), n-hexyl acrylate (2) and cyclohexyl acrylate (3) yielding the corresponding water soluble host/guest complexes 1a–3a. The complexes were copolymerized in water by free radical mechanism and the reactivity ratios were determined by measuring the monomer consumption by HPLC. The following reactivity ratios were found: copolymerization of 1a and 2a: r1= 1.01 ± 0.01; r2= 1.04 ± 0.01; copolymerization of 3a and 2a: r1= 0.74; r2= 1.28; copolymerization of 3a and 1a: r1= 0.75 ± 0.04; r2= 1.13 ± 0.01. In contrast to that, the copolymerization of the uncomplexed monomers 1–3 in organic medium (DMF…
Characterization of the Cyclodextrin−Surfactant Interactions by Volume and Enthalpy
2003
Volume and enthalpy of transfer of hydroxypropyl-α-cyclodextrin (HP-α-CD) and hydroxypropyl-γ-cyclodextrin (HP-γ-CD) from water to the aqueous solutions of sodium alkanoates (sodium hexanoate, sodium decanoate and sodium dodecanoate) were determined at 298 K. The cyclodextrin concentration was kept constant, and that of the surfactant was varied in order to analyze both the pre- and postmicellar regions. The experimental data in the premicellar region were consistent with the formation of 1:1 and 1:2 (1 cyclodextrin:2 surfactants) inclusion complexes, with the exception of the HP-α-CD/sodium dodecanoate system which presented only the 1:1 complexes. The mechanism of the 1:2 complexes format…
Temperature-responsive inclusion complex of cationic PNIPAAM diblock copolymer and γ-cyclodextrin
2012
Aqueous mixtures of γ-cyclodextrin (γ-CD) and the thermosensitive cationic diblock copolymer poly(N-isopropylacrylamide)-b-poly(3-acrylamidopropyl)trimethylammonium chloride (PNIPAAM24-b-PAMPTAM(+)9) or the PNIPAAM homopolymer PNIPAAM47 have been investigated using various experimental methods. Solid γ-CD–polymer inclusion complexes (pseudopolyrotaxanes) form at ambient temperatures in fairly concentrated CD solutions. The NMR measurements showed that the stoichiometry of the inclusion complexes is close to two NIPAAM units per CD molecule. The cationic block of the copolymer is not incorporated into the CD cavity. Synchrotron radiation X-ray diffraction spectra of the solid inclusion compl…
Thermodynamic Evidence of Cyclodextrin−Micelle Interactions
2002
The enthalpy of transfer (ΔHt) of hydroxypropyl-α-cyclodextrin (HP-α-CD), hydroxypropyl-β-cyclodextrin (HP-β-CD), and β-cyclodextrin (β-CD) from water to the aqueous C6F13CO2Na and C7F15CO2Na solutions were determined in the pre- and post-micellar regions. The behavior of the macrocycles is system specific. Generally, the magnitude of the enthalpy is influenced by several factors: (1) the alkyl chain length of the surfactant, (2) the cyclodextrin cavity and its alkylation, (3) the interactions between the free cyclodextrin and the free surfactant, (4) the host−guest equilibrium constant, (5) the host/guest stoichiometry, and (6) the micelle-cyclodextrin (free and/or complexed) interactions…
Chemical and pharmaceutical evaluation of the relationship between triazole linkers and pore size on cyclodextrin–calixarene nanosponges used as carr…
2016
Mixed cyclodextrin–calixarene nanosponges were used to prepare some composites with the well known polyphenolic bioactive compounds quercetin and silibinin. The composites were characterized by means of different techniques (UV-vis, FT-IR, microcalorimetry, thermogravimetry), in order to assess their loading and thermal stability. The kinetics of release of the bioactive molecules into aqueous solution were studied at two different pH values (1.0, 6.4), which mimic typical physiological conditions. Finally the possible antiproliferative effects in vitro were assayed towards three triple negative breast cancer cell lines (SUM 149, SUM 159 and MDA-MB-23). Our results point out the role assume…
Heat Capacity Study to Evidence the Interactions between Cyclodextrin and Surfactant in the Monomeric and Micellized States
2003
The heat capacities of transfer (ΔCpt) of hydroxypropyl-α-cyclodextrin and hydroxypropyl-γ-cyclodextrin (0.05 mol kg-1) from water to aqueous solutions of sodium hexanoate, sodium decanoate, and so...
Nanoparticle Vesicles Through Self Assembly of Cyclodextrin- and Adamantyl-Modified Silica
2010
Stable nanoparticle vesicles were for the first time prepared from adamantyl- and cyclodextrin (CD)-modified silica nanoparticles forming host-guest interactions in aqueous solution. Adamantyl-functionalized nanoparticles were obtained from thiol-isocyanate reaction of thiol-modified nanoparticles with 1-adamantyl isocyanate. The CD modified silica particles were isolated from a reaction of mono-6-para-toluenesulfonyl-β-cyclodextrin with the thiol functionalized silica under microwave conditions in basic media. The obtained particles were characterized in respect of agglomeration and self-assembly behavior in aqueous solution by dynamic light scattering and transmission electron microscopy.…
Water-soluble, cyclodextrin-functionalized semiconductor nanocrystals: Preparation and pH-dependent aggregation and emission properties
2009
Abstract Using peramino-functionalized β-cyclodextrin molecules for phase.transfer of hydrophobic CdSe multishell nanocrystals into water, we obtained hydrophilic nanoparticles with high quantum yield (up to 50%). At pH > 9, the aqueous solution of these nanocrystals remained stable for several months. The nanoparticles showed a strong influence of the pH of the aqueous solution on the emission of the nanocrystals: the quantum yield varied reversible from ∼10% at pH=6 to ∼50% at pH=14, an effect which according to particle size characterization by dynamic light-scattering and asymmetric flow field-flow fractionation has mainly been attributed to reversible partial aggregation of the hydroph…