An enzyme/pH dual-responsive supramolecular fluorescent vesicle with tunable size fabricated by europium complex and polypseudorotaxanes

The fluorescent vesicles based on lanthanide ions are considered as an ideal biomimetic optical nanoplatform for simulating biological processes of cell membrane. However, the accurately and controllably adjusting the size of vesicles based on lanthanides while ensuring their fluorescence performance and stability still remains a challenge. Herein, a dual-stimuli-responsive fluorescent supramolecular vesicle with tunable size has been designed based on host-guest interaction and coordinating aggregation. Europium complexes can be encapsulated within supramolecular assemblies by assembling with polypseudorotaxanes (PPRs), which are formed by F127 and carboxymethyl-β-cyclodextrin (CMCD) through host-guest interaction. The fluorescence properties of the europium complexes have been significantly enhanced by confining and shielding them within vesicles. Upon the addition of α-amylase and HCl, the fluorescence intensity of the vesicles will gradually and significantly quench as a result of CMCD degradation and dissociation of the europium complexes. This research presents a convenient method for regulating the size of lanthanide fluorescent vesicles, and the supramolecular vesicles obtained with multi-stimuli response are anticipated to be utilized in the diagnosis of relevant diseases and targeted drug delivery.