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Structure formation in injectable poly(lactide‐ co ‐glycolide) depots. II. Nature of the gel
Author(s) -
Wang Liwei,
Venkatraman Subbu,
Gan Leong Huat,
Kleiner Lothar
Publication year - 2004
Publication title -
journal of biomedical materials research part b: applied biomaterials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.665
H-Index - 108
eISSN - 1552-4981
pISSN - 1552-4973
DOI - 10.1002/jbm.b.30147
Subject(s) - differential scanning calorimetry , materials science , polymer , copolymer , lactide , kinetics , polymer chemistry , rheometry , chemical engineering , solvent , chemistry , composite material , organic chemistry , thermodynamics , physics , quantum mechanics , engineering
The benzyl benzoate solutions of poly( D , L ‐lactide‐ co ‐glycolide), a random oriented synthesized copolymer with L/G ratio of 50:50, have been shown to form gels during aging and upon injection into buffer or water. The gelation properties influence drug release kinetics for these injectable, depot‐forming solutions. In this article, we report on the mechanism of gelation. We find that only polymers that have a certain average block length of glycolide units form gels during aging as well as depots upon in vitro . Thus, gel formation is likely due to the formation of ordered solvated aggregates of blocky glycolide units. Rheometry, differential scanning calorimetry, and nuclear magnetic resonance were used to investigate the gelation kinetics and the polymer molecular parameters. Of all the polymers used, poly(lactide‐ co ‐glycolide)s with glycolide average block length <2.9 did not show any gelation behavior. The details of the gelation process are also solvent dependent. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 72B: 215–222, 2005