title: Preparation of an amphiphilic triblock copolymer with pH- and thermo-responsiveness and self-assembled micelles applied to drug release.
abstract: A novel amphiphilic ABC triblock copolymer, poly(N-isopropylacrylamide)-b-poly(styrene-alternate-maleic anhydride)-b-polystyrene (PNIPAAm-b-PSMA-b-PSt), was designed and synthesized by reversible addition fragmentation chain transfer polymerization. The copolymer can disperse in aqueous media at room temperature to self-assemble into pH- and thermo-responsive core-shell-corona micelles, with the hydrophobic PSt block as core, the pH-sensitive PSMA block as shell, and the thermo-sensitive PNIPAAm block as corona. The aqueous copolymer solutions exhibited lower critical solution temperature (LCST) values around 33.5-35 degrees C under pH 2.1-9.2 conditions via optical transmittance measurements. The critical micelle concentration values of the self-assembled micelles were about 18.6 mg/L at pH 2.1 and 21.1 mg/L at pH 6.9, respectively, relying on fluorescent probe techniques. An interesting pH- and thermo-dependent size of the micelles was observed by dynamic light scattering techniques, which showed that the micelle diameters were about 100-120 nm at 40 degrees C and 120-160 nm at 25 degrees C, corresponding to pH 2.1-9.2, respectively. Transmission electron microscopy observations showed that the resulting micelles as uniform nanoparticles existed in regularly spherical shapes. The folic acid-loaded micelles showed a remarkable pH- and thermo-responsive drug release behavior. These results indicate that the copolymer micelles may serve as a promising "intelligent" drug delivery system.
authors.affiliation: Institute of Fine Chemical and Engineering, Henan University, Kaifeng, 475001 Henan, People's Republic of China.
authors.forename: Tianhong
authors.initials: T
authors.lastname: Qu
authors.forename: Airong
authors.initials: A
authors.lastname: Wang
authors.forename: Jinfang
authors.initials: J
authors.lastname: Yuan
authors.forename: Qingyu
authors.initials: Q
authors.lastname: Gao
mesh_terms: D000178:Acrylamides; D000180:Acrylic Resins; D004337:Drug Carriers / Q000737:chemistry*; D016503:Drug Delivery Systems / Q000379:methods; D006863:Hydrogen-Ion Concentration; D008298:Maleates; D008823:Micelles; D011108:Polymers / Q000737:chemistry*; D011137:Polystyrenes; D013696:Temperature
chemical_list: D000178:Acrylamides; D000180:Acrylic Resins; D004337:Drug Carriers; D008298:Maleates; D008823:Micelles; D011108:Polymers; D011137:Polystyrenes; C520889:poly(styrene-alt-maleic anhydride); C052970:poly-N-isopropylacrylamide; C067295:N-isopropylacrylamide