Supramolecular nanoparticles constructed from pillar[5]arene-based host–guest complexation with enhanced aggregation-induced emission for imaging-guided drug delivery

Fluorophores with aggregation-induced emission (AIE) characteristics have attracted more and more attention due to their unparalleled advantages in terms of sensitivity and photostability, and have been extensively utilized for disease diagnosis and therapy. However, it remains challenging to restrict the intramolecular rotation of the AIE luminogens (AIEgens) both in solution and aggregated states. Herein, we utilize host–guest chemistry to achieve this meaningful goal by using a carboxylate-modified pillar[5]arene H as a supramolecular host and an AIEgen containing a tetraphenylethene core G as a guest. The AIE effect of the fluorophore is effectively enhanced upon the formation of an inclusion host–guest complex H⊃G, and the fluorescence of H⊃G is much more intensive than that of free G. Supramolecular nanoparticles (SNPs) with high emission are prepared from H⊃G using a nanoprecipitation method, which can be used as a fluorescent probe for living cell imaging showing superior photostability against laser excitation. Intriguingly, the formed SNPs act as nanocarriers to encapsulate doxorubicin (DOX) to deactivate both the fluorescence of SNPs and DOX caused by the energy transfer relay (ETR) effect, which is mediated by Forster resonance energy transfer and aggregation-caused quenching. The release of loaded DOX after cellular internalization interrupts the ETR effect to light up the silenced fluorescence, thus allowing in situ visualization of drug release. More importantly, the anticancer efficacy of the loaded drug is greatly maintained using this sophisticated supramolecular system, showing promising potential in imaging-guided drug delivery.