Light induced molecular release from vesicles based on amphiphilic linear-dendritic block copolymers

We report on the synthesis and characterization of new amphiphilic linear-dendritic block copolymers (LDBCs) as well as their self-assembly in water to form polymeric vesicles. We have also investigated the encapsulation of both hydrophilic and hydrophobic fluorescent probes by these stimuli-responsive polymeric vesicles and the use of light as an external stimulus to trigger the release of the probes. The LDBCs are composed of a 2000 g mol−1 poly(ethylene glycol) (PEG) linear segment linked to a fourth generation 2,2-di(hydroxymethyl)propionic acid (bis-MPA) based dendron with 4-isobutyloxyazobenzene units at the periphery. By tuning the chemical structure of the azobenzene moieties, a specific LDBC has been identified that forms stable vesicles in water as it is clearly revealed by TEM and Cryo-TEM images. Encapsulation of both hydrophobic and hydrophilic molecules by these vesicular self-assemblies has been investigated by fluorescence analysis as well as the release of the loaded probes triggered by low intensity UV illumination, which is related to trans-to-cis isomerisation of the azobenzene moieties. Thus, the potential of these photo-responsive vesicles as light-responsive nanocarriers is demonstrated.