Less Is More: Donor Engineering of a Stable Molecular Dye for Bioimaging in the NIR-IIb Window

Area of Science:

• Biophotonics
• Molecular Imaging
• Organic Chemistry

Background:

• Fluorescence molecular imaging requires enhanced clarity, especially in the near-infrared IIb (NIR-IIb) window (1500-1700 nm).
• Existing dyes often face limitations in stability and performance within this spectral range.

Purpose of the Study:

• To develop a novel small-molecule dye for superior performance in NIR-IIb fluorescence imaging.
• To investigate the molecular design principles for achieving enhanced emission and stability in the NIR-IIb window.

Main Methods:

• Designed a novel small-molecule dye, DA-5, based on cyanine dye principles.
• Engineered an asymmetric donor-π-acceptor (D-π-A) architecture with a single methine bridge.
• Evaluated DA-5's photophysical properties, stability, and aggregation behavior in aqueous solution.

Main Results:

• DA-5 exhibits emission at 1088 nm, suitable for NIR-IIb imaging.
• The dye demonstrates excellent chemo- and photostability, resistance to solvatochromism, and antiaggregation properties.
• DA-5 possesses a large Stokes shift (241 nm) and high brightness (321 M⁻¹ cm⁻¹).
• High-performance in vivo imaging was achieved, including lymphatic system, intestinal vessels, whole-body angiography, and cerebral/hindlimb microvasculature.

Conclusions:

• The developed DA-5 dye offers a promising solution for high-performance NIR-IIb fluorescence imaging.
• The molecular design strategy of asymmetric D-π-A architecture is effective for advancing in vivo biophotonics.
• DA-5 enables detailed visualization of complex biological systems, paving the way for new diagnostic and research applications.