Cucurbit[8]uril Induced Molecular Folding Cascade Assembly for NIR Targeted Cell Imaging

Abstract A macrocyclic confinement‐activated green phosphorescence and two‐photon near‐infrared (NIR) fluorescence supramolecular cascade assembly is constructed by multivalent interaction based on the alkyl‐bridged triphenylamine‐vinyl pyridine salts (BTPA), cucurbit[8]uril (CB[8]), β‐cyclodextrin‐grafted hyaluronic acid (HACD), and 4‐bromophenyl pyridine salt and CB[8] complex (PY/CB[8]). Taking advantage of CB[8]‐induced macrocyclic confinement and molecular folding, the fluorescence of BTPA is effectively redshifted by 30 nm from 720 to 750 nm. Subsequently, HACD, a cancer cell targeting agent, is co‐assembled with a BTPA/CB[8] supramolecular folder to form a nanoparticle, further enhancing NIR fluorescence from 750 nm up to 810 nm through cascade confinement. Upon introduction of the 2:1 complex PY/CB[8], multicomponent nanoparticles are fabricated, not only showing efficient NIR fluorescence with an increase in quantum yield from 7.21% to 22.92% but also endowing green phosphorescence emission, which is successfully applied for two‐photon cancer cell‐targeted imaging to shield background interference from fluorescent and phosphorescent resources.