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Preparation and characterization of pH- and temperature-sensitive pullulan microspheres for controlled release of drugs

Paper ID Volume ID Publish Year Pages File Format Full-Text
9863 650 2008 9 PDF Available
Title
Preparation and characterization of pH- and temperature-sensitive pullulan microspheres for controlled release of drugs
Abstract

Most 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 = 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.

Keywords
Intelligent microspheres; pH/thermo-responsive copolymers; Pullulan; Lower critical solution temperature; Drug deliveryAAm, acrylamide; AIBN, N,N′-azobisisobutyronitrile; CAN, cerium ammonium nitrate; CP, cloud point; 4-DMAP, 4-dimethylamino pyridine; IPB
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Preparation and characterization of pH- and temperature-sensitive pullulan microspheres for controlled release of drugs
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Publisher
Database: Elsevier - ScienceDirect
Journal: Biomaterials - Volume 29, Issue 18, June 2008, Pages 2767–2775
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us