Intrinsic Near-Infrared-II Fluorescent Nanozymes Support High-Resolution Imaging and Tumor Catalytic Immunotherapy

Area of Science:

• Biomedical Engineering
• Nanotechnology
• Materials Science

Background:

• Nanozymes show promise for in vivo therapy due to enzyme-mimicking properties.
• Challenges include real-time tracking and biosafety of nanozymes.
• Metal-free nanozymes are desirable for reduced toxicity.

Purpose of the Study:

• To develop single-component, metal-free autofluorescent nanozymes (AFNZs) with enhanced near-infrared fluorescence (NIR-II FL) and multienzyme activities.
• To enable high-contrast in vivo imaging and catalytic tumor therapy.
• To establish a stoichiometry-guided strategy for AFNZ construction.

Main Methods:

• Solvothermal conversion of cyanine precursors with controlled sulfur/nitrogen (S/N) stoichiometry.
• Characterization of fluorescence properties (quantum yield, emission wavelength) and enzyme-like activities (peroxidase, catalase, oxidase).
• In vivo studies for deep-tissue tumor imaging, angiography, and image-guided tumor resection.

Main Results:

• Developed metal-free AFNZs with ultrabright NIR-II FL (QY >1.4%, λem >1100 nm), a 20-fold enhancement over precursors.
• AFNZs exhibited potent peroxidase, catalase, and oxidase activities.
• Achieved deep-tissue tumor imaging (~8 mm), high-resolution angiography (~30 µm), and image-guided resection of microtumors.

Conclusions:

• The developed AFNZs offer superior performance for in vivo imaging and image-guided therapy compared to precursors and ICG.
• Stoichiometry control is a viable strategy for creating intrinsically fluorescent metal-free nanozymes.
• AFNZs show potential for advanced applications in image-guided catalytic immunotherapy.