Cucurbit[8]Uril Driven Upconversion Near-Infrared Delayed Fluorescence for Targeted Cell Imaging.

Area of Science:

• Supramolecular Chemistry
• Bioimaging
• Organic Electronics

Background:

• Pure organic upconversion systems enable deep-tissue bioimaging via efficient two or three-photon excitation.
• Room-temperature phosphorescence (RTP) upconversion is crucial for advanced imaging techniques.

Purpose of the Study:

• To develop a pure organic RTP upconversion supramolecular assembly for near-infrared (NIR) delayed fluorescence.
• To enhance fluorescence and achieve efficient phosphorescence resonance energy transfer (PERT) for bioimaging applications.

Main Methods:

• Co-assembly of cucurbit[8]uril (CB[8])-confined indole-bridged xanthene derivative (CyBr) with PySO3⊂CB[8], guided by β-cyclodextrin-grafted hyaluronic acid (HACD).
• Utilizing spatial confinement of CB[8] for fluorescence enhancement and HACD for cascade fluorescence boosting.
• Employing multivalent interactions within β-CD cavities for efficient PERT.

Main Results:

• Achieved a 10-fold fluorescence enhancement of CyBr via CB[8] confinement.
• Boosted CyBr quantum yield (QY) by 22 times using HACD.
• Demonstrated 84.49% PERT efficiency, leading to NIR delayed fluorescence at 710 nm with a 99.16 µs lifetime.

Conclusions:

• The developed supramolecular assembly exhibits exceptional upconversion capability under 940 nm three-photon excitation.
• Enables targeted A549 cancer cell imaging with deep-tissue penetration.
• Provides long-lived NIR emission for low-background detection in bioimaging.