title: A pH dependent thermo-sensitive copolymer drug carrier incorporating 4-amino-2,2,6,6-tetramethylpiperidin-1-oxyl (4-NH2-TEMPO) residues for electron spin resonance (ESR) labeling.
abstract: The fabrication of a new amphiphilic block copolymer composed of a poly DL-lactic acid (PLA) hydrophobic backbone and pH dependent thermo-sensitive poly (N-isopropyl) methacrylamide-co-N-isopropylmaleamic acid-co-10-undecenoic acid (PNIPAAm-co-NIPMMA-co-UA) entities as hydrophilic domains as well as carrying 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) residues for electron spin resonance (ESR) labeling is reported. The lower critical solution temperature (LCST) of the copolymer was determined by optical absorbance measurements. The LCST was pH dependent and varied in a narrow practical range, 35.4 °C at pH 5.0, 37.5 °C at pH 6.5 and 39.4 °C at pH 7.4, which was below, near and above nominal physiological temperature respectively. The assembly of the copolymer into micelles in aqueous solution at temperatures below the LCST was confirmed by FT-IR, (1)H NMR and fluorescence spectroscopy. It is demonstrated that the anticancer drug, 5-fluorouracil (5-FU) can be loaded effectively within the polymeric micelles and released in response to environmental stimuli- namely, pH and temperature.
authors.affiliation: Shanghai Key Laboratory of Functional Materials Chemistry, and Research Centre of Analysis and Test, East China University of Science and Technology, Shanghai 200237, PR China.
authors.forename: Ronghua
authors.initials: R
authors.lastname: Yu
authors.forename: Hongli
authors.initials: H
authors.lastname: Zhao
authors.forename: Zijun
authors.initials: Z
authors.lastname: Zhao
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Wan
authors.forename: Huihui
authors.initials: H
authors.lastname: Yuan
authors.forename: Minbo
authors.initials: M
authors.lastname: Lan
authors.forename: Leonard F
authors.initials: LF
authors.lastname: Lindoy
authors.forename: Gang
authors.initials: G
authors.lastname: Wei
mesh_terms: D003497:Cyclic N-Oxides / Q000737:chemistry*; D004337:Drug Carriers / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D005472:Fluorouracil / Q000008:administration & dosage; D006863:Hydrogen-Ion Concentration; D008823:Micelles; D011108:Polymers / Q000737:chemistry*; D013113:Spin Labels; D013696:Temperature
chemical_list: D003497:Cyclic N-Oxides; D004337:Drug Carriers; D008823:Micelles; D011108:Polymers; D013113:Spin Labels; D005472:Fluorouracil; C003959:TEMPO