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BioMed Research International
Volume 2014 (2014), Article ID 579212, 10 pages
Research Article

Impact of Core-Forming Segment Structure on Drug Loading in Biodegradable Polymeric Micelles Using PEG-b-Poly(lactide-co-depsipeptide) Block Copolymers

1Organization for Research and Development of Innovative Science and Technology (ORDIST), Kansai University, 3-3-35 Yamate, Suita, Osaka 564-8680, Japan
2Department of Chemistry and Materials Engineering, Faculty of Chemistry, Materials and Bioengineering, Kansai University, 3-3-35 Yamate, Suita, Osaka 564-8680, Japan

Received 13 December 2013; Accepted 30 December 2013; Published 20 February 2014

Academic Editor: Inn-Kyu Kang

Copyright © 2014 Akihiro Takahashi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We synthesized series of amphiphilic AB-type block copolymers having systematic variation in the core-forming segments using poly(lactide-co-depsipeptide)s as a hydrophobic segment and prepared polymeric micelles using the block copolymers, PEG-b-poly(lactide-co-depsipeptide). We then discussed the relationship between the core-forming segment structure and drug loading efficiency for the polymeric micelles. PEG-b-poly(lactide-co-depsipeptide)s, PEG-b-PLGL containing l-leucine (Leu), and PEG-b-PLGF containing l-phenylalanine (Phe), with similar molecular weights and various mole fractions of depsipeptide units, were synthesized. Polymeric micelles entrapping model drug (fluorescein, FL) were prepared using these copolymers. As a result, PEG-b-poly(lactide-co-depsipeptide) micelles showed higher drug loading compared with PEG-b-PLLA and PEG-b-PDLLA as controls. The drug loading increased with increase in the mole fraction of depsipeptide unit in the hydrophobic segments. The introduction of aliphatic and aromatic depsipeptide units was effective to achieve higher FL loading into the micelles. PEG-b-PLGL micelle showed higher drug loading than PEG-b-PLGF micelle when the amount of FL in feed was high. These results obtained in this study should be useful for strategic design of polymeric micelle-type drug delivery carrier with high drug loading efficiency.