title: Reversibly Switching Bilayer Permeability and Release Modules of Photochromic Polymersomes Stabilized by Cooperative Noncovalent Interactions.
abstract: We report on the fabrication of photochromic polymersomes exhibiting photoswitchable and reversible bilayer permeability from newly designed poly(ethylene oxide)-b-PSPA (PEO-b-PSPA) diblock copolymers, where SPA is spiropyran (SP)-based monomer containing a unique carbamate linkage. Upon self-assembling into polymersomes, SP moieties within vesicle bilayers undergo reversible phototriggered isomerization between hydrophobic spiropyran (SP, λ2 > 450 nm irradiation) and zwitterionic merocyanine (MC, λ1 < 420 nm irradiation) states. For both SP and MC polymersomes, their microstructures are stabilized by multiple cooperative noncovalent interactions including hydrophobic, hydrogen bonding, π-π stacking, and paired electrostatic (zwitterionic) interactions, with the latter two types being exclusive for MC polymersomes. Control experiments using analogous block copolymers of hydrophobic SP monomer with a carbonate linkage (SPO) and conventional spiropyran methacrylate monomer (SPMA) containing a single ester functionality were then conducted, revealing that carbamate-incurred hydrogen bonding interactions in PEO-b-PSPA are crucial for polymersome stabilization in the zwitterionic MC state. Moreover, reversible phototriggered SP-to-MC polymersome transition is accompanied by membrane polarity and permeability switching from being nonimpermeable to selectively permeable toward noncharged, charged, and zwitterionic small molecule species below critical molar masses. Intriguingly, UV-actuated MC polymersomes possess two types of release modules: (1) sustained release upon short UV irradiation duration by taking advantage of the unexpectedly slow spontaneous MC-to-SP transition kinetics (t1/2 > 20 h) under dark conditions; (2) on-demand and switchable release under alternated UV-vis light irradiation. We further demonstrate photoswitchable spatiotemporal release of 4',6-diamidino-2-phenylindole (DAPI, cell nuclei-staining dye) within living HeLa cells.
authors.affiliation: CAS Key Laboratory of Soft Matter Chemistry, Hefei National Laboratory for Physical Sciences at the Microscale, iChem (Collaborative Innovation Center of Chemistry for Energy Materials), Department of Polymer Science and Engineering, University of Science and Technology of China , Hefei, Anhui 230026, China.
authors.forename: Xiaorui
authors.initials: X
authors.lastname: Wang
authors.affiliation: CAS Key Laboratory of Soft Matter Chemistry, Hefei National Laboratory for Physical Sciences at the Microscale, iChem (Collaborative Innovation Center of Chemistry for Energy Materials), Department of Polymer Science and Engineering, University of Science and Technology of China , Hefei, Anhui 230026, China.
authors.forename: Jinming
authors.initials: J
authors.lastname: Hu
authors.affiliation: CAS Key Laboratory of Soft Matter Chemistry, Hefei National Laboratory for Physical Sciences at the Microscale, iChem (Collaborative Innovation Center of Chemistry for Energy Materials), Department of Polymer Science and Engineering, University of Science and Technology of China , Hefei, Anhui 230026, China.
authors.forename: Guhuan
authors.initials: G
authors.lastname: Liu
authors.affiliation: Engineering and Materials Science Experiment Center, University of Science and Technology of China , Hefei, Anhui 230027, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Tian
authors.affiliation: Engineering and Materials Science Experiment Center, University of Science and Technology of China , Hefei, Anhui 230027, China.
authors.forename: Huijuan
authors.initials: H
authors.lastname: Wang
authors.affiliation: Engineering and Materials Science Experiment Center, University of Science and Technology of China , Hefei, Anhui 230027, China.
authors.forename: Ming
authors.initials: M
authors.lastname: Gong
authors.affiliation: CAS Key Laboratory of Soft Matter Chemistry, Hefei National Laboratory for Physical Sciences at the Microscale, iChem (Collaborative Innovation Center of Chemistry for Energy Materials), Department of Polymer Science and Engineering, University of Science and Technology of China , Hefei, Anhui 230026, China.
authors.forename: Shiyong
authors.initials: S
authors.lastname: Liu
mesh_terms: D008051:Lipid Bilayers; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D011108:Polymers / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D008051:Lipid Bilayers; D011108:Polymers