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.
journal_name
Biomaterialsjournal_title
Biomaterialsauthors
Fundueanu G,Constantin M,Ascenzi Pdoi
10.1016/j.biomaterials.2008.03.025subject
Has Abstractpub_date
2008-06-01 00:00:00pages
2767-75issue
18eissn
0142-9612issn
1878-5905pii
S0142-9612(08)00180-4journal_volume
29pub_type
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