1,720,982 research outputs found
Poly(N-isopropylacrylamide-co-acrylamide) cross-linked thermoresponsive microspheres obtained from preformed polymers: Influence of the physico-chemical characteristics of drugs on their release profiles
No full textPoly(vinyl alcohol) microspheres with pH- and thermosensitive properties as temperature-controlled drug delivery
No full textFast-responsive porous thermoresponsive microspheres for controlled delivery of macromolecules
No full textPreparation and characterization of pH- and temperature-sensitive pullulan microspheres for controlled release of drugs
No full textMost part of pH- and temperature-sensitive microspheres used for the controlled delivery of drugs are
not biodegradable. Therefore, the aim of this work is to prepare pH- and temperature-sensitive microspheres
from biodegradable and biocompatible natural polymers. Pullulan microspheres were prepared
by suspension cross-linking with epichlorohydrin of an aqueous solution of the polymer. In order to
confer them temperature sensitivity, poly(N-isopropylacrylamide-co-acrylamide) was grafted onto pullulan
microspheres. Then, the pH-sensitive units (–COOH) were introduced by reaction between the
remaining –OH groups of the pullulan with succinic anhydride. The grafted pullulan microspheres are
more hydrophilic than pullulan microspheres, their swelling degree as well as water regain increase
significantly. The thermo-sensitivity of the carboxylated microspheres depends to the number and the
ionization form (–COOH/–COO) of carboxylic groups. At a low exchange capacity (0.35 meq/g), microspheres
are thermo-sensitive both in the protonated and deprotonated form of –COOH groups. At
a higher exchange capacity (2.25 meq/g), microspheres are almost unswellable in the protonated form
and swell extensively in the ionized form (up to 28 times than their dried form) loosing in a great extent
the thermo-sensitive properties. In isotonic phosphate buffer pH 1⁄4 7.4, both thermo-sensitive and pH/
thermo-sensitive microspheres possess a phase transition temperature close to that of the human body
temperature. Loading and release profiles of lysozyme, taken as a molecular model system, were
investigated
pH- and temperature-sensitive polymeric microspheres for drug delivery: the dissolution of copolymers modulates drug release
No full text
Do cyclodextrins bound to dextran microspheres act as sustained delivery systems of drugs?
No full textAn intelligent multicompartmental system based on thermo-sensitive starch microspheres for temperature-controlled release of drugs
No full textLower critical solution temperature versus volume phase transition temperature in thermoresponsive drug delivery systems
No full textAminated polysaccharide microspheres as DNA delivery systems
No full textThis article describes the production and characterization of cationic microparticles based on pullulan and starch for the delivery of nucleic acids. The microparticles were prepared by chemically cross-linkinking of a polymer solution dispersed in organic phase, followed by amination with N, N-diethyl-2-chloroethyl amine hydrochloride, or N-glycidyl-N,N-dimethyl-N-methylammonium chloride. The association of desoxyribonucleotide (DNA) with positively charged microparticles was determined. The association capacity and the affinity of microspheres for DNA were investigated as a function of type of polysaccharide, content and basicity of the amino groups. It was found that the both types of carriers synthetized display a high affinity for defibrotide due to the high porosity of polysaccharide microspheres (PMs). The in vitro release kinetics from microspheres showed an initial fast release of DNA (30 min) followed by slower release rate over 14 days. DNA release was influenced by the ionic strength of the receiving fluid. In addition, DNA release was slightly more rapid from pullulan than from starch complexes. DNA stability studies were performed by agarose gel, indicating no degradation even after 14 days. All the produced cationic microspheres were able to quantitatively load DNA. The release of DNA from PMs was strongly affected by the ionic strength of the receiving fluid. Finally, agarose gel electrophoresis of DNA released from microspheres indicated that no DNA degradation occurs even after 14 days of release from PMs
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