Search results for "polymers"
showing 10 items of 3567 documents
NEW SELF-ASSEMBLING POLYASPARTYLHYDRAZIDE COPOLYMER MICELLES FOR ANTICANCER DRUG DELIVERY.
2010
A new amphiphilic copolymer have been synthesized starting from the hydrosoluble polyaspartylhydrazide (PAHy) polymer, by grafting both hydrophilic PEG(2000) chains and hydrophobic palmitic acid (C(16)) moieties on polymer backbone, and the structure of obtained PAHy-PEG(2000)-C(16) copolymer have been characterized by 2D (1)H/(13)C NMR experiments. PAHy-PEG(2000)-C(16) copolymer showed the ability of self-assembling in aqueous media giving a core-shell structure and resulted potentially useful for encapsulating and dissolving hydrophobic drug. The formation of micellar core-shell structure has been investigated by 2D (1)H NMR NOESY experiments. The presence of cross-peaks for protons of C(…
Reversibly stable thiopolyplexes for intracellular delivery of genes.
2006
Novel polyaspartamide non-viral carriers for gene therapy were synthesized by introducing, on the same polymer backbone, positively charged groups, for electrostatic interactions with DNA, and thiol groups for the formation of disulfide bridges between polymer chains. The introduction of thiols was aimed to have a vector with low redox potential sensitivity: disulfide crosslinking in fact, being stable in extracellular environment, allowed either to have stable complexes in plasma, that can protect DNA from metabolism, or to be reduced inside the cell, where the excess of glutathion in reduced form maintains a low redox potential. The consequent destabilization of the complex after disulfid…
Fluoropolymer Based on a Polyaspartamide containing 1,2,4-Oxadiazole Units: A Potential Artificial Oxygen (O2) Carrier
2007
Abstract In this preliminary work we have prepared a fluorinated polymer capable of solubilizing an appreciable amount of O(2) and, at the same time, maintaining a higher water solubility than perfluoroalkanes investigated as injectable O(2) carriers. In particular, we describe the synthesis and characterization of a new macromolecular conjugate obtained by derivatization of alpha,beta-poly(N-2-hydroxyethyl)-DL-aspartamide (PHEA) with 5-pentafluorophenyl-3-perfluoroheptyl-1,2,4-oxadiazole, called PHEA-F. This new water soluble fluoropolymer was prepared in high yield using a simple procedure. It was characterized by FT-IR and UV-vis spectrophotometry, (19)F-NMR and SEC measurements. O(2) so…
Galactosylated micelles for a ribavirin prodrug targeting to hepatocytes.
2013
Polymeric micelles potentially able to carry to hepatocytes a ribavirin (RBV) prodrug, exploiting the presence of carbohydrate receptors, that is, ASGPR, were prepared starting from a galactosylated polylactide-polyaminoacid conjugate. This latter was obtained by chemical reaction of α,β-poly(N-2-hydroxyethyl) (2-aminoethylcarbamate)-dl-aspartamide (PHEA-EDA) with polylactic acid (PLA), and subsequent reaction with lactose, obtaining PHEA-EDA-PLA-GAL copolymer. To enhance the entrapment into obtained nanostructures, a hydrophobic RBV prodrug, that is, RBV tripalmitate, was synthesized and its capability to release RBV in the presence of an adequate enzymatic activity was demonstrated. Liver…
How Low Can You Go? Low Densities of Poly(ethylene glycol) Surfactants Attract Stealth Proteins.
2018
It is now well-established that the surface chemistry and “stealth” surface functionalities such as poly(ethylene glycol) (PEG) chains of nanocarriers play an important role to decrease unspecific protein adsorption of opsonizing proteins, to increase the enrichment of specific stealth proteins, and to prolong the circulation times of the nanocarriers. At the same time, PEG chains are used to provide colloidal stability for the nanoparticles. However, it is not clear how the chain length and density influence the unspecific and specific protein adsorption keeping at the same time the stability of the nanoparticles in a biological environment. Therefore, this study aims at characterizing the…
Pegylated nanoparticles based on a polyaspartamide. Preparation, physico-chemical characterization and intracellular uptake
2006
Nanoparticles with different surface PEGylation degree were prepared by using as starting material alpha,beta-poly(N-2-hydroxyethyl)-d,l-aspartamide (PHEA). PHEA was functionalized with a PEG amino-derivative for obtaining PHEA-PEG(2000) copolymer. Both PHEA and PHEA-PEG(2000) were derivatized with methacrylic anhydride (MA) for obtaining poly(hydroxyethylaspartamide methacrylated) (PHM) and poly(hydroxyethylaspartamide methacrylated)-PEGylated (PHM-PEG(2000)), respectively. Nanoparticles were obtained by UV irradiation of an inverse microemulsion, using as internal phase an aqueous solution of PHM alone or of the PHM/PHM-PEG(2000) mixture at different weight ratio and as external phase a m…
SELF-ASSEMBLED AMPHIPHILIC HYALURONIC ACID GRAFT COPOLYMERS FOR TARGETED RELEASE OF ANTITUMORAL DRUG
2009
Polymeric micelles obtained by self-assembling of amphiphilic hyaluronic acid (HA) graft copolymers have been prepared and characterized. In particular, hyaluronic acid (HA) has been grafted to polylactic acid (PLA) and polyethylenglycol chains (PEG), then the copolymers able to form micelles in aqueous medium have been chosen to entrap the antitumoral drug Doxorubicin. The critical aggregation concentration of HA-g-PLA or HA-g-PLA-g-PEG micelles has been determined by using pyrene as a fluorescent probe, whereas their shape and size have been evaluated by light scattering measurements, scanning and transmission electron microscopies. The selective cytotoxicity of drug loaded micelles towar…
Self-assembling and auto-crosslinkable hyaluronic acid hydrogels with a fibrillar structure
2008
Abstract A hyaluronic acid derivative bearing pendant l -benzoyl-cysteine portions (with a derivatization degree equal to 10 mol.%) was synthesized by linking N,N′-dibenzoyl- l -cystine to the polysaccharide and then reducing its disulfide bridge to thiol groups. The formation of π–π stacking interactions between the benzoyl moieties was studied by fluorescence spectroscopy as a function of polymer concentration and oxidation time. The efficiency of oxidation of thiol groups to disulfide bridges occurring in phosphate buffer pH 7.4, was determined by colorimetric assays. The hydrogel formed by means of oxidative crosslinking has shown the presence of fibrillar aggregates as detected by ligh…
End Capping Ring-Opening Olefin Metathesis Polymerization Polymers with Vinyl Lactones
2008
The selective placement of a functional group at the chain end of a ring-opening metathesis polymer using ruthenium carbene initiators has been a significant limitation. Here we demonstrate a highly effective and facile end-capping technique for ROMP with living ruthenium carbene chain ends using single-turnover olefin metathesis substrates. Vinylene carbonate and 3H-furanone are introduced as functionalization and termination agents for the ruthenium-initiated ring-opening metathesis polymerization. This leads directly to the formation of functional polymer end groups without further chemical transformation steps. Aldehyde and carboxylic acid end groups can be introduced by this new method…
Rotational Correlation Functions of Single Molecules
2004
Single molecule rotational correlation functions are analyzed for several reorientation geometries. Even for the simplest model of isotropic rotational diffusion our findings predict non-exponential correlation functions to be observed by polarization sensitive single molecule fluorescence microscopy. This may have a deep impact on interpreting the results of molecular reorientation measurements in heterogeneous environments.