PH-triggered decomposition of polymeric fluorescent vesicles to induce growth of tetraphenylethylene nanoparticles for long-term live cell imaging

Abstract

Self-assembly schemes provide a simple and tunable approach to creating a myriad of well-defined nanostructures from design of macromolecules in bulk, thin film and solution environments. Here we demonstrated a facile method to construction of tetraphenylethylene nanoparticles (TPE NPs) by decomposition-assembly from pH-responsive and AIE-characteristic vesicles, which were self-assembled by an amphiphilic PEG750-POSS-(TPE)7 polymer in aqueous solutions. The introduction of Schiff base bonds furnished the fluorescent polymersomes with unique pH responsiveness that is stable under physiological conditions but quickly degradable in acidic environments. Interestingly, the luminous vesicles were transformed into spherical TPE NPs in a solution of lower pH on account of the synergetic combination of cleavage rate of the Schiff base bonds and guidance effect of the entangled tadpole-shaped polymeric chains. The AIE feature of TPE molecule was completely retained in the TPE NPs. Compared to the pH-responsive PEG750-POSS-(TPE)7 vesicles, these AIE-active TPE NPs possessed stable morphology and adjustable size by manipulation of the incubation time. These TPE NPs can be quickly internalized into the tumors through endocytosis pathway and retain strong blue luminescence inside the living cells for a long period, presenting the good photostability and biological imaging property. Cytotoxicity assay revealed that TPE NPs were biocompatible and thus can be utilized for long-term live cell imaging and biomedical applications.