We report on the fabrication of photochromic polymersomes exhibiting photoswitchable and reversible bilayer permeability from newly de-signed 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 photo-triggered isomeriza-tion 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 poly-mersomes. control experiments using analogous block copolymers of hydrophobic sp monomer with a carbonate linkage (spo) and conven-tional 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 photo-triggered sp-to-mc polymersome transition is accompanied with membrane polarity and permeability switching from being non-impermeable to selectively permeable towards non-charged, 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.
J. Am. Chem. Soc., Just Accepted Manuscript
DOI: 10.1021/jacs.5b10127
Publication Date (Web): November 19, 2015
http://pubs.acs.org/doi/abs/10.1021/jacs.5b10127
