Tunable Nano-Supramolecules Based on Cucurbiturils for Near-Infrared Phosphorescence Imaging

Nano-supramolecules based on artificial macrocycles can not only regulate assembly morphology but also boost phosphorescence resonance energy transfer (PRET). Herein, a water-soluble phosphorescence supramolecule was constructed from the hyaluronic acid-modified bromophenylpyridinium (HAPY), cucurbit[n]uril (CB[n], n = 7/8), and energy acceptor phenyl-bridged phenothiazine derivatives, displaying efficient PRET and achieving near-infrared (NIR) phosphorescence by macrocyclic CB[n] and the assembly confinements. As compared with weak phosphorescent nanofibers of HAPY/CB[7], the spherical nanoparticles of HAPY/CB[8] not only gave strong green phosphorescence with extended lifetime to 1.27 ms but also could act as the energy donor and confine cationic phenothiazine in the secondary assemblies, leading to highly efficient PRET efficiency (87.27%) from the phosphors to triplet acceptors, realizing phosphorescence emission at 750 nm and an ultralarge Stokes shift of 440 nm. Ultimately, the nanoassembly achieved by the multiscale confinements boosting PRET was successfully applied in targeted cancer cell imaging, providing new insight for fabricating NIR phosphorescence materials.