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

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]), & beta;-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.

Automated summary

A macrocyclic confinement-activated green phosphorescence and two-photon near-infrared (NIR) fluorescence supramolecular cascade assembly has been constructed by multivalent interaction. Through the use of CB[8]-induced macrocyclic confinement and molecular folding, the fluorescence of BTPA is effectively redshifted, and NIR fluorescence is enhanced through cascade confinement. Introduction of the PY/CB[8] complex leads to the fabrication of multicomponent nanoparticles, showing efficient NIR fluorescence and green phosphorescence emission for two-photon cancer cell-targeted imaging.