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Polymeric Aggregates (polymeric + aggregate)
Selected AbstractsBinding and release studies of a cationic drug from a star-shaped four-arm poly(ethylene oxide)- b -poly(methacrylic acid)JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 2 2010E. He Abstract Star-shape polymers possess higher densities of terminal functional groups and three-dimensional tetrahedron structure that induce significantly different association and interactions with drug compared to linear structure of identical molecular weights. Four-arm poly(ethylene oxide)- b -poly(methacrylic acid) block copolymer was synthesized by atom transfer radical polymerization technique, and it self-assembled into core-shell micelles and extended unimers at low and high pH respectively. The negatively charged carboxylate groups on the polymer chains interacted with a cationic drug through electrostatic interaction forming polymer/drug complexes stabilized by biocompatible hydrophilic PEO segments. The hydrodynamic radius (Rh) of the polymeric aggregates and polymer/drug complexes ranged from 46 to 84,nm and 32 to 55,nm at pH of 4.6 and 8.0 respectively, making them suitable for drug delivery applications. The thermodynamic parameters and interactions between polymer and drug were determined by isothermal titration calorimetric technique. The electrostatic force, hydrogen bonding and hydrophobic interactions controlled the characteristics of polymer/drug formation and complexes when the molar ratios of drug and polymer were varied. Drug selective electrode system was used to measure the dynamic release of imipramine hydrochloride (IPH) from multi-arm PEO- b -PMAA star polymer. The release exponent n was greater than 0.5 indicating a non-Fickian type diffusion behavior, where the release behavior was dominated by chain relaxation induced by ion exchange that was dependent on pH. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:782,793, 2010 [source] Synthesis and properties of biomimetic poly(L -glutamate)- b -poly(2-acryloyloxyethyllactoside)- b -poly(L -glutamate) triblock copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2004Chang-Ming Dong Abstract A novel class of biomimetic glycopolymer,polypeptide triblock copolymers [poly(L -glutamate),poly(2-acryloyloxyethyllactoside),poly(L -glutamate)] was synthesized by the sequential atom transfer radical polymerization of a protected lactose-based glycomonomer and the ring-opening polymerization of ,-benzyl- L -glutamate N -carboxyanhydride. Gel permeation chromatography and nuclear magnetic resonance analyses demonstrated that triblock copolymers with defined architectures, controlled molecular weights, and low polydispersities were successfully obtained. Fourier transform infrared spectroscopy of the triblock copolymers revealed that the ,-helix/,-sheet ratio increased with the poly(benzyl- L -glutamate) block length. Furthermore, the water-soluble triblock copolymers self-assembled into lactose-installed polymeric aggregates; this was investigated with the hydrophobic dye solubilization method and ultraviolet,visible analysis. Notably, this kind of aggregate may be useful as an artificial polyvalent ligand in the investigation of carbohydrate,protein recognition and for the design of site-specific drug-delivery systems. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5754,5765, 2004 [source] Reduction-Sensitive Self-Aggregates as a Novel Delivery SystemMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 8 2010Ju Eun Kim Abstract Methoxy PEG amine with molecular weight of 5k and , -caprolactone with molecular weight of 1,960 were conjugated to a peptide comprising three cysteine residues. The shift of peak molecular weight and narrow molecular weight distribution in GPC trace without any noticeable shoulder as well as 1H NMR analysis confirmed the successful synthesis of the copolymer. A modified O/W dialysis system was employed to prepare self-aggregates having the size around 210,nm. During the dialysis, stabilized aggregates were obtained by intermolecular disulfide bonds via oxidation. Critical aggregate concentration (CAC) of the copolymer was determined as 0.07,mg,·,mL,1 and disulfide-stabilized self-aggregates remained stable regardless of the concentration without displaying CAC. Doxorubicin-loading amount and efficiency was 8.7 and 26.0%, respectively. Release profile of doxorubicin below CAC at 37,°C showed a sustained release and the addition of D,L -dithiothreitol (DTT) after 24,h triggered a burst release of doxorubicin. Intermolecular disulfide bonds via oxidation stabilized the polymeric aggregates even in the diluted condition similar to that in the bloodstream and addition of DTT destabilized the aggregates to burst encapsulated doxorubicin in the reductive condition. [source] RAFT Synthesis and Solution Properties of pH-Responsive Styrenic-Based AB Diblock Copolymers of 4-Vinylbenzyltrimethylphosphonium Chloride with N,N -DimethylbenzylvinylamineMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 21 2007Andrew B. Lowe Abstract The RAFT synthesis and solution properties of AB block copolymers of 4-vinylbenzyltrimethylphosphonium chloride (TMP) and N,N -dimethylbenzylvinylamine (DMBVA) is described. The pH-dependent self-assembly properties of the AB diblock copolymers were examined using of 1H NMR, DLS, and fluorescence spectroscopy. The size of the polymeric aggregates depends on the block copolymer composition/molecular mass. The self assembly is completely reversible, as predicted from the tunable hydrophilicity/hydrophobicity of the DMBVA residues. The AB diblock copolymers can be effectively locked in the self-assembled state using a straightforward core crosslinking reaction between the tertiary amine residues of DMBVA and difunctional 1,4-bis(bromomethyl)benzene. [source] Temperature-Triggered Nanosphere Formation Through Self-Assembly of Amphiphilic PolyphosphazeneMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 14 2006Jian Xiang Zhang Abstract Summary: An amphiphilic graft polyphosphazene with a molar ratio of poly(N -isopropylacrylamide) (PNIPAm) to ethyl glycinate (GlyEt) of 0.54:1 was synthesized. This copolymer in aqueous solution exhibited two temperature induced phase transitions at 17.2 and 33.7,°C, which correspond to the transformation of primary aggregate morphology (at Tph1) and the collapse of PNIPAm chains (at Tph2) respectively. Network micelles were assembled in water at lower temperature (far below Tph1), and then narrowly dispersed nanoparticles were formed above Tph1, while inter-nanoparticle aggregation occurred due to the collapse of PNIPAm chains surrounding the GlyEt core when the temperature was above Tph2. Through solubilization of the hydrophobic drug ibuprofen into polymeric aggregates at lower temperature, drug loaded nanospheres were prepared successfully. In vitro release revealed that sustained drug release was achieved with this novel delivery system. These results suggest that this novel copolymer could be used as a potential drug carrier, especially for the delivery of hydrophobic biocompounds through parenteral administration. Schematic illustration of the temperature-triggered self-assembly process of PNIPAm/GlyEt-PPP in aqueous solution. [source] | ||||||||||