title: A novel, smart microsphere with K(+)-induced shrinking and aggregating properties based on a responsive host-guest system.
abstract: A novel type of smart microspheres with K(+)-induced shrinking and aggregating properties is designed and developed on the basis of a K(+)-recognition host-guest system. The microspheres are composed of cross-linked poly(N-isopropylacrylamide-co-acryloylamidobenzo-15-crown-5) (P(NIPAM-co-AAB15C5)) networks. Due to the formation of stable 2:1 "sandwich-type" host-guest complexes between 15-crown-5 units and K(+) ions, the P(NIPAM-co-AAB15C5) microspheres significantly exhibit isothermally and synchronously K(+)-induced shrinking and aggregating properties at a low K(+) concentration, while other cations (e.g., Na(+), H(+), NH4(+), Mg(2+), or Ca(2+)) cannot trigger such response behaviors. Effects of chemical compositions of microspheres on the K(+)-induced shrinking and aggregating behaviors are investigated systematically. The K(+)-induced aggregating sensitivity of the P(NIPAM-co-AAB15C5) microspheres can be enhanced by increasing the content of crown ether units in the polymeric networks; however, it is nearly not influenced by varying the monomer and cross-linker concentrations in the microsphere preparation. State diagrams of the dispersed-to-aggregated transformation of P(NIPAM-co-AAB15C5) microspheres in aqueous solutions as a function of temperature and K(+) concentration are constructed, which provide valuable information for tuning the dispersed/aggregated states of microspheres by varying environmental K(+) concentration and temperature. The microspheres with synchronously K(+)-induced shrinking and aggregating properties proposed in this study provide a brand-new model for designing novel targeted drug delivery systems.
authors.affiliation: School of Chemical Engineering, Sichuan University , Chengdu, Sichuan 610065, P. R. China.
authors.forename: Ming-Yue
authors.initials: MY
authors.lastname: Jiang
authors.forename: Xiao-Jie
authors.initials: XJ
authors.lastname: Ju
authors.forename: Lu
authors.initials: L
authors.lastname: Fang
authors.forename: Zhuang
authors.initials: Z
authors.lastname: Liu
authors.forename: Hai-Rong
authors.initials: HR
authors.lastname: Yu
authors.forename: Lu
authors.initials: L
authors.lastname: Jiang
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.forename: Rui
authors.initials: R
authors.lastname: Xie
authors.forename: Qianming
authors.initials: Q
authors.lastname: Chen
authors.forename: Liang-Yin
authors.initials: LY
authors.lastname: Chu
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D043844:Crown Ethers / Q000737:chemistry*; D016503:Drug Delivery Systems / Q000379:methods; D008863:Microspheres; D010316:Particle Size; D011188:Potassium / Q000737:chemistry*; D013696:Temperature
chemical_list: D000180:Acrylic Resins; D043844:Crown Ethers; C052970:poly-N-isopropylacrylamide; C042148:15-crown-5; D011188:Potassium
keywords: K+-recognition; aggregation; microspheres; phase transition; responsive host−guest system