Microstructure transition of hydrophilic modified ibuprofen and Pluronic copolymer F127 complexes
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ORIGINAL CONTRIBUTION
Microstructure transition of hydrophilic modified ibuprofen and Pluronic copolymer F127 complexes Duo Wei & Lingling Ge & Rong Guo
Received: 25 July 2012 / Revised: 29 September 2012 / Accepted: 13 November 2012 / Published online: 30 November 2012 # Springer-Verlag Berlin Heidelberg 2012
Abstract The effect of the aggregation state of Pluronic copolymer (PEO100–PPO65–PEO100, F127) and the concentration of hydrophilic modified ibuprofen (Ibuprofen– PEG800, IP800) on the interaction between F127 and IP800 was systematically investigated by nuclear magnetic resonance, dynamic light scatter (DLS), surface tension, and freeze-fractured transmission electron microscopy. In the solution of F127 unimers (5 °C), F127 unimers tended to wrap around IP800 micelles, and the binding model of F127 unimers to IP800 micelles transferred from wrapping around to partly threading through with increasing IP800 concentration. The latter binding model was straightly confirmed by nuclear Overhauser enhancement spectroscopy. As the aggregation state of F127 is in the beginning of the micellization (20 °C), the addition of IP800 significantly promoted the micellization of F127 to form the F127/IP800 complex with F127 micelles as the skeleton called the F127–micelle complex. The sudden decrease of the size obtained from DLS stemmed from the disruption of the F127–micelle complex and accompanying rehydration of PPO which is weaker compared with refs. The amount of IP800 to disintegrate the F127–micelle complex increased in the F127–micelle-dominated solution (40 °C) compared to that at 20 °C. Keywords Hydrophilic modification . NOESY . Chemical shift . Binding models
Electronic supplementary material The online version of this article (doi:10.1007/s00396-012-2859-8) contains supplementary material, which is available to authorized users. D. Wei : L. Ge : R. Guo (*) School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou, People’s Republic of China e-mail: [email protected]
Introduction Amphiphilic copolymers, poly (ethylene oxides)–poly (propylene oxides)–poly (ethylene oxides) (PEO–PPO–PEO), are produced by BASF under the trade name Pluronic. Pluronic copolymers with low toxicity, biodegradability, designability, and thermosensitivity are widely studied in experimental medicine and pharmaceutical sciences, and recognized as pharmaceutical excipients listed in the US and British Pharmacopoeia [1]. One of the most interesting features of the copolymers is the self-assembly in aqueous solution [2–10]. At lower temperatures or copolymer concentrations, the copolymers act as individual unimers. As the temperature higher than critical micellar temperature or the concentration above the critical micellar concentration (cmc), the unimers associate to form micelles with PPO blocks as the core and PEO chains as water-swollen corona. The application of the copolymers in drug delivery originally focuses on the solubilization issue of water-insoluble drugs and the preparation of stable micellar formulations
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