title: Thermo- and pH-Responsive Copolymers Bearing Cholic Acid and Oligo(ethylene glycol) Pendants: Self-Assembly and pH-Controlled Release.
abstract: A family of block and random copolymers of norbornene derivatives bearing cholic acid and oligo(ethylene glycol) pendants were prepared in the presence of Grubbs' catalyst. The phase transition temperature of the copolymers in aqueous solutions may be tuned by the variation of comonomer ratios and pH values. Both types of copolymers formed micellar nanostructures with a hydrophilic poly(ethylene glycol) shell and a hydrophobic core containing cholic acid residues. The micellar size increased gradually with increasing pH due to the deprotonation of the carboxylic acid groups. These micelles were capable of encapsulating hydrophobic compounds such as Nile Red (NR). A higher hydrophobicity/hydrophilicity ratio in both copolymers resulted in a higher loading capacity for NR. With similar molecular weights and monomer compositions, the block copolymers showed a higher loading capacity for NR than the random copolymers. The NR-loaded micelles exhibited a pH-triggered release behavior. At pH 7.4 within 96 h, the micelles formed by the block and random of copolymers released 56 and 97% NR, respectively. Therefore, these micelles may have promise for use as therapeutic nanocarriers in drug delivery systems.
authors.affiliation: Département de Chimie, Université de Montréal , C.P. 6128, Succursale Centre-ville, Montréal, QC H3C 3J7, Canada.
authors.forename: Yong-Guang
authors.initials: YG
authors.lastname: Jia
authors.affiliation: Département de Chimie, Université de Montréal , C.P. 6128, Succursale Centre-ville, Montréal, QC H3C 3J7, Canada.
authors.forename: X X
authors.initials: XX
authors.lastname: Zhu
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry; D002264:Carboxylic Acids / Q000737:chemistry; D002384:Catalysis; D019826:Cholic Acid / Q000737:chemistry; D003692:Delayed-Action Preparations / Q000737:chemistry; D004337:Drug Carriers / Q000737:chemistry; D005026:Ethylene Glycols / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D008970:Molecular Weight; D049329:Nanostructures / Q000737:chemistry; D010078:Oxazines / Q000737:chemistry; D010316:Particle Size; D011092:Polyethylene Glycols / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D013696:Temperature
chemical_list: D001672:Biocompatible Materials; D002264:Carboxylic Acids; D003692:Delayed-Action Preparations; D004337:Drug Carriers; D005026:Ethylene Glycols; D008823:Micelles; D010078:Oxazines; D011108:Polymers; D011092:Polyethylene Glycols; D019826:Cholic Acid; C044808:nile red
keywords: cholic acid; oligo(ethylene glycol); pH-controlled release; self-assembly; thermo- and pH-responsive