TY - JOUR
T1 - Preparation and characterization of thermally responsive block copolymer micelles comprising poly(N-isopropylacrylamide-b-DL-lactide)
AU - Kohori, Fukashi
AU - Sakai, Kiyotaka
AU - Aoyagi, Takao
AU - Yokoyama, Masayuki
AU - Sakurai, Yasuhisa
AU - Okano, Teruo
N1 - Funding Information:
Part of this work was supported by the Ministry of Education, Science, Sports and Culture, Japan (Grant 08672569). The authors are grateful to Dr. David W. Grainger, Colorado State University, for his valuable discussion on this research.
PY - 1998/10/30
Y1 - 1998/10/30
N2 - The thermally sensitive block copolymer, poly(N-isopropylacrylamide-b-dl-lactide) (PIPAAm-PLA), was synthesized by ring-opening polymerization of dl-lactide initiated from hydroxy-terminated poly (N-isopropylacrylamide) (PIPAAm). A PIPAAm bearing a single terminal hydroxyl group was prepared by telomerization using 2-hydroxyethanethiol as a chain-transfer agent. Successful preparation of PIPAAm and the PIPAAm-PLA block copolymer was verified by gel permeation chromatography (GPC) and 1H-NMR spectroscopy. Polymeric micelles were prepared from block copolymers using a dialysis method. Their solutions showed reversible changes in optical properties: transparent below a lower critical solution temperature (LCST) and opaque above the LCST. Dynamic light scattering measurements were used to observe the formation of micellar structures approximately 40 nm in diameter, which do not change between 20°C and 30°C. Above the LCST, polymer micelles aggregated, a phenomenon found to be reversible since the aggregates dissociated again by cooling below the LCST. Further observations using atomic force microscopy (AFM) confirmed this behaviour. The properties of this block copolymer system are interesting from both applied and fundamental perspectives, particularly for active targeting as drug carriers. Copyright (C) 1998 Elsevier Science B.V.
AB - The thermally sensitive block copolymer, poly(N-isopropylacrylamide-b-dl-lactide) (PIPAAm-PLA), was synthesized by ring-opening polymerization of dl-lactide initiated from hydroxy-terminated poly (N-isopropylacrylamide) (PIPAAm). A PIPAAm bearing a single terminal hydroxyl group was prepared by telomerization using 2-hydroxyethanethiol as a chain-transfer agent. Successful preparation of PIPAAm and the PIPAAm-PLA block copolymer was verified by gel permeation chromatography (GPC) and 1H-NMR spectroscopy. Polymeric micelles were prepared from block copolymers using a dialysis method. Their solutions showed reversible changes in optical properties: transparent below a lower critical solution temperature (LCST) and opaque above the LCST. Dynamic light scattering measurements were used to observe the formation of micellar structures approximately 40 nm in diameter, which do not change between 20°C and 30°C. Above the LCST, polymer micelles aggregated, a phenomenon found to be reversible since the aggregates dissociated again by cooling below the LCST. Further observations using atomic force microscopy (AFM) confirmed this behaviour. The properties of this block copolymer system are interesting from both applied and fundamental perspectives, particularly for active targeting as drug carriers. Copyright (C) 1998 Elsevier Science B.V.
KW - Poly(DL-lactide)
KW - Poly(N-isopropylacrylamide)
KW - Polymeric micelles
KW - Thermally sensitive
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U2 - 10.1016/S0168-3659(98)00023-6
DO - 10.1016/S0168-3659(98)00023-6
M3 - Article
C2 - 9795019
AN - SCOPUS:0031751919
SN - 0168-3659
VL - 55
SP - 87
EP - 98
JO - Journal of Controlled Release
JF - Journal of Controlled Release
IS - 1
ER -