Fabrication of Multiresponsive Shell Cross-Linked Micelles Possessing pH-Controllable Core Swellability and Thermo-Tunable Corona Permeability

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• 作者：Xiaoze Jiang ; Zhishen Ge ; Jian Xu ; Hao Liu ; Shiyong Liu
• 刊名：Biomacromolecules
• 出版年：2007
• 出版时间：October 2007
• 年：2007
• 卷：8
• 期：10
• 页码：3184 - 3192
• 全文大小：395K
• 年卷期：v.8,no.10(October 2007)
• ISSN：1526-4602

文摘

A double hydrophilic ABC triblock copolymer, poly(2-(diethylamino)ethyl methacrylate)-b-poly(2-(dimethylamino)ethyl methacrylate)-b-poly(N-isopropylacrylamide) (PDEA-b-PDMA-b-PNIPAM), containing the well-knownpH-responsive PDEA block and thermoresponsive PNIPAM block, was synthesized by atom transfer radicalpolymerization via sequential monomer addition using ethyl 2-chloropropionate as the initiator. The obtainedtriblock copolymer exhibits interesting "schizophrenic" micellization behavior in aqueous solution, andsupramolecularly self-assembles into three-layer "onion-like" PNIPAM-core micelles at acidic pH's and elevatedtemperatures and PDEA-core micelles with "inverted" structures at alkaline pH's and room temperature. In bothcases, dynamic laser light scattering (LLS) and optical transmittance reveal the presence of near-monodispersemicelles, and the micelle formation/inversion process is fully reversible. Novel shell cross-linked (SCL) micelleswith pH-responsive PDEA cores and thermoresponsive PNIPAM coronas were then facilely fabricated from thePDEA-b-PDMA-b-PNIPAM triblock copolymer by cross-linking the PDMA inner shells with 1,2-bis(2-iodoethoxy)ethane. The reversible pH-dependent swelling/shrinking of PDEA cores and thermosensitive collapse/aggregationof PNIPAM coronas of the obtained SCL micelles were investigated in detail by dynamic LLS, optical transmittance,and transmission electron microscopy. As the structurally stable SCL micelles possess pH-controllable coreswellability and thermo-tunable corona permeability, the release profile of a model hydrophobic drug, dipyridamole,initially loaded within the hydrophobic PDEA core, can be dually controlled by both the solution pH and thetemperature. This represents the first report of SCL micelles with multiresponsive cores and coronas, which mayfind practical applications in fields such as drug delivery and smart release.