A Supramolecular Radical Dimer: High-Efficiency NIR-II Photothermal Conversion and Therapy

Area of Science:

• Biomedical Engineering
• Materials Science
• Chemistry

Background:

• Photothermal therapy (PTT) utilizes light to generate heat for therapeutic purposes.
• The near-infrared II (NIR-II) biowindow (1000-1350 nm) offers enhanced tissue penetration depth for PTT.
• Developing efficient NIR-II absorbing materials is crucial for advancing PTT.

Purpose of the Study:

• To create a novel supramolecular radical dimer with strong absorption in the NIR-II biowindow.
• To evaluate the photothermal conversion efficiency and stability of the developed material.
• To assess the efficacy of the material in inhibiting cancer cells using NIR-II irradiation.

Main Methods:

• Fabrication of a supramolecular radical dimer using N,N'-dimethylated dipyridinium thiazolo[5,4-d]thiazole radical cation (MPT^.+) and cucurbit[8]uril (CB[8]).
• Characterization of the dimer's absorption properties in the NIR-II region.
• In vitro evaluation of photothermal conversion efficiency and HegG2 cancer cell inhibition under 1064 nm irradiation.
• Assessment of tissue penetration capability using chicken breast tissue model.

Main Results:

• The supramolecular radical dimer (2MPT^.+-CB[8]) exhibited strong absorption within the NIR-II biowindow.
• Highly efficient photothermal conversion and improved stability were observed for the dimer.
• Significant inhibition of HegG2 cancer cells was achieved under NIR-II irradiation, demonstrating efficacy even through tissue.
• The material showed potential for deep tissue penetration, a key advantage of NIR-II PTT.

Conclusions:

• A novel NIR-II absorbing supramolecular radical dimer was successfully constructed.
• This material offers a promising platform for effective NIR-II photothermal therapy.
• The study presents a new strategy for designing organic radical-based NIR-II chromophores with potential applications in luminescence, optoelectronics, and biosensing.