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Phase Transition Behavior of Novel pH‐Sensitive Polyaspartamide Derivatives Grafted with 1‐(3‐Aminopropyl)imidazole
Author(s) -
Seo Kwangwon,
Kim Dukjoon
Publication year - 2006
Publication title -
macromolecular bioscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.924
H-Index - 105
eISSN - 1616-5195
pISSN - 1616-5187
DOI - 10.1002/mabi.200600076
Subject(s) - imidazole , chemistry , protonation , polymer , dynamic light scattering , ethylene glycol , polymer chemistry , organic chemistry , materials science , nanoparticle , nanotechnology , ion
Summary: New pH‐sensitive polyaspartamide derivatives were synthesized by grafting 1‐(3‐aminopropyl)imidazole and/or O ‐(2‐aminoethyl)‐ O ′‐methylpoly(ethylene glycol) 5000 on polysuccinimide for application in intracellular drug delivery systems. The DS of 1‐(3‐aminopropyl)imidazole was adjusted by the feed molar ratio, and the structure of the prepared polymer was confirmed using FT‐IR and 1 H NMR spectroscopy. Their pH‐sensitive properties were characterized by light transmittance measurements, and the particle size and its distribution were investigated by dynamic light scattering measurements at varying pH values. The pH‐sensitive phase transition was clearly observed in polymer solutions with a high substitution of 1‐(3‐aminopropyl)imidazole. The prepared polymers showed a high buffering capacity between pH 5 and 7, and this increased with the DS of 1‐(3‐aminopropyl)imidazole. The pH dependence of the aggregation and de‐aggregation behavior was examined using a fluorescence spectrometer. For MPEG/imidazole‐ g ‐polyaspartamides with a DS of 1‐(3‐aminopropyl)imidazole over 82%, self aggregates associated with the hydrophobic interactions of the unprotonated imidazole groups were observed at pH values above 7, and their mean size was over 200 nm, while the aggregates of polymers were dissociated at pH values below 7 by the protonation of imidazole groups. These pH‐sensitive polyaspartamide derivatives are potential basic candidates for intracellular drug delivery carriers triggered by small pH changes.Mean particle size change of MPEG/imidazole‐ g ‐polyaspartamide as pH is varied.