title: Self-assembly of polypeptide-containing ABC-type triblock copolymers in aqueous solution and its pH dependence.
abstract: Self-assembling of novel biodegradable ABC-type triblock copolymer poly(ethylene glycol)-poly(L-lactide)-poly(L-glutamic acid) (PEG-PLLA-PLGA) is studied. In aqueous media, it self-assembles into a spherical micelle with the hydrophobic PLLA segment in the core and the two hydrophilic segments PEG and PLGA in the shell. With the lengths of PEG and PLLA blocks fixed, the diameter of the micelles depends on the length of the PLGA block and on the volume ratio of H(2)O/dimethylformamide (DMF) in the media. When the PLGA block is long enough, morphology of the self-assembly is pH-dependent. It assembles into the spherical micelle in aqueous media at pH 4.5 and into the connected rod at or below pH 3.2. The critical micelle concentration (cmc) of the copolymer changes accordingly with decreasing solution pH. Both aggregation states can convert to each other at the proper pH value. This reversibility is ascribed to the dissociation and neutralization of the COOH groups in the LGA residues. When the PLGA block is short compared to the PEG or PLLA block, it assembles only into the spherical micelle at various pH values.
authors.affiliation: State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People's Republic of China.
authors.forename: Jing
authors.initials: J
authors.lastname: Sun
authors.forename: Chao
authors.initials: C
authors.lastname: Deng
authors.forename: Xuesi
authors.initials: X
authors.lastname: Chen
authors.forename: Haijun
authors.initials: H
authors.lastname: Yu
authors.forename: Huayu
authors.initials: H
authors.lastname: Tian
authors.forename: Jingru
authors.initials: J
authors.lastname: Sun
authors.forename: Xiabin
authors.initials: X
authors.lastname: Jing
mesh_terms: D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000737:chemistry*; D008027:Light; D046911:Macromolecular Substances / Q000737:chemistry; D008823:Micelles; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D010455:Peptides / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D011100:Polyglycolic Acid / Q000737:chemistry*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers / Q000737:chemistry*; D012542:Scattering, Radiation; D012995:Solubility; D012997:Solvents / Q000737:chemistry; D014867:Water / Q000737:chemistry*
chemical_list: D046911:Macromolecular Substances; D008823:Micelles; D010455:Peptides; D011108:Polymers; D012997:Solvents; D014867:Water; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D011092:Polyethylene Glycols