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ABSTRACT: Comb-shaped copolymers comprised of hydrophobic and hydrophilic blocks are self-assembled in aqueous solution, which results that they are suitable for delivery of hydrophobic drug molecules. Chitosan (CS) is an important biomaterial used widely in medical applications. Herein, a comb-shaped cationic copolymer composed of long biocompatible CS main chains and short PNIPAAm side chains was prepared via atom transfer radical polymerization (ATRP) by attaching an ATRP initiating group to N-phthaloyl chitosan. By subsequent removal of the protective groups on N-phthaloyl chitosan-graft-poly(N-isopropylacrylamide) (PHCS-g-PNIPAAm) copolymer with N(2)H(4)·H(2)O lead to the polymer pendant amino groups, this study attempted to synthesize a pH/temperature multi-responsive material. This chitosan-graft-poly(N-isopropylacrylamide) (CS-g-PNIPAAm) copolymer is self-assembled in aqueous solution into stimuli-responsive core-shell micelles with hydrodynamic diameters of about 170nm. Structural organization and solution behavior were then investigated utilizing (1)H NMR spectroscopy, transmission electron microscopy (TEM) and dynamic light scattering (DLS).
Carbohydrate polymers. 01/2013; 92(1):621-8.
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ABSTRACT: A well-defined thermoresponsive poly(ethylene glycol)-block-poly(N-isopropylacrylamide)-block-poly(ε-caprolactone) (PEG(43)-b-PNIPAM(82)-b-PCL(87)) triblock copolymer was synthesized by combination of atom transfer radical polymerization (ATRP), ring-opening polymerization (ROP), and click chemistry. The synthesis included the four steps, and all the structures of the polymers were determined. The thermoresponsive triblock copolymer can disperse in water at room temperature to form core-shell-corona micelles with the hydrophobic PCL block as core, the thermoresponsive PNIPAM block as shell, and the hydrophilic PEG block as corona. At temperatures above the lower critical solution temperature (LCST) of the PNIPAM block, the PNIPAM chains gradually collapse on the PCL core to shrink the size and change the structure of the resultant core-shell-corona micelles with temperature increasing.
The Journal of Physical Chemistry B 11/2011; 115(50):14947-55. · 3.70 Impact Factor
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ABSTRACT: Hydrogels based on sodium alginate (SA) have already been widely used in biomedical applications using Ca(2+) as a cross-linker; however, these hydrogels tend to disintegrate in electrolyte solutions. To solve this problem, we present a kind of oxidized sodium alginate (OSA) microgel using water-soluble chitosan (WSC) as a cross-linker. This microgel was successfully prepared via an emulsion cross-linking technique at room temperature. The microgel was cross-linked by the formation of both Schiff base bonds and interpolyelectrolyte complexes, which can efficiently eliminate the disintegration of the microgel in electrolyte solutions. Morphological properties of the resulting microgels were determined by transmission electron microscopy (TEM), hydrodynamic diameters of the microgels were characterized by dynamic light scattering (DLS). The objective of this work was to achieve the colon-specific delivery of an anti-ulcerative colitis drug. 5-Aminosalicylic acid (5-ASA) was chosen as a model drug and the in vitro drug-release profile was established in buffer solutions with 0.1 M HCl/NaCl (pH 1.2) and 0.1 M phosphate-buffered saline (PBS, pH 7.4) at 37°C. The microgel was incubated in 0.1 M PBS (pH 7.4) at 37°C to determine its degradation behavior. Cell cytotoxicity (tested by MTT assay) showed that this microgel had no significant cytotoxicity. These results indicated that this microgel prepared by introducing WSC into OSA may have potential applications in oral controlled drug-delivery systems. Therefore, the OSA/WSC microgel may be a useful carrier for the colon-specific delivery of anti-inflammatory drugs including 5-ASA and the enhanced therapeutic effect of ulcerative colitis.
Journal of Biomaterials Science Polymer Edition 09/2011; · 1.69 Impact Factor
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ABSTRACT: The aim of this study was to prepare oxidized guar gum with a simple dry method, basing on guar gum, hydrogen peroxide and a small amount of solvent. To obtain a product with suitable viscosity for reactive dye printing, the effects of various factors such as the amount of oxidant and solvent, reaction temperature and time were studied with respect to the viscosity of reaction products. The product was characterized by Fourier transform infrared spectroscopy, size exclusion chromatography, scanning electron microscopy and differential scanning calorimetry. The hydrated rate of guar gum and oxidized guar gum was estimated through measuring the required time when their solutions (1%, w/v) reached the maximum viscosity. The effects of the salt concentration and pH on viscosity of the resultant product were studied. The mixed paste containing oxidized guar gum and carboxymethyl starch was prepared and its viscosity was determined by the viscometer. The rheological property of the mixed paste was appraised by the printing viscosity index. In addition, the applied effect of mixed paste in reactive dye printing was examined by assessing the fabric stiffness, color yield and sharp edge to the printed image in comparison with sodium alginate. And the results indicated that the mixed paste could partially replace sodium alginate as thickener in reactive dye printing. The study also showed that the method was low cost and eco-friendly and the product would have an extensive application in reactive dye printing.
International journal of biological macromolecules 09/2011; 49(5):1083-91. · 2.37 Impact Factor
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ABSTRACT: Covalent functionalization of azide-modified SiO(2) with well-defined, alkyne-terminated poly(N-isopropylacrylamide) was accomplished by the Cu(I)-catalyzed [3 + 2] Huisgen cycloaddition. The alkyne-terminated RAFT chain transfer agent was first synthesized, and then the alkyne-terminated thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) with different molecular weights were synthesized by the RAFT of NIPAM monomer. The polymerization kinetics and the evolution of number-average molecular weights (M(n)), and polydispersities (M(w)/M(n)), with monomer conversions were investigated. A copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) "grafting to" method was used to attach thermoresponsive polymers onto the exterior surface of SiO(2) nanoparticles which produced relatively high grafting density. The as-synthesized hybrid nanoparticles showed thermoresponsive behavior and were characterized by FTIR, XPS, TGA, DLS, and TEM, etc.
ACS Applied Materials & Interfaces 08/2011; 3(8):3215-23. · 4.53 Impact Factor
