Conjugated Oligoelectrolytes for Long-Term Tumor Tracking with Incremental NIR-II Emission

Area of Science:

• Organic Chemistry
• Biomedical Imaging
• Materials Science

Background:

• Conjugated oligoelectrolytes (COEs) are promising for bioimaging due to their tunable optical properties.
• Near-infrared-II (NIR-II) imaging offers deeper tissue penetration and reduced background autofluorescence compared to visible light imaging.
• Developing water-soluble, low-toxicity NIR-II probes with enhanced cellular emission is crucial for in vivo applications.

Purpose of the Study:

• To design and synthesize a novel NIR-II emissive conjugated oligoelectrolyte, COE-BBT.
• To evaluate the photophysical properties, solubility, and biocompatibility of COE-BBT.
• To demonstrate the utility of COE-BBT for in vitro and in vivo tumor imaging.

Main Methods:

• Synthesis and characterization of the conjugated oligoelectrolyte COE-BBT.
• Measurement of solubility, cytotoxicity, and photophysical properties (emission quantum yield) in aqueous media and lipid bilayers.
• Confocal microscopy for in vitro cell imaging.
• In vivo imaging of intracranial and subcutaneous tumors in mice using NIR-II emission.

Main Results:

• COE-BBT exhibits high aqueous solubility (>50 mg mL-1) and low toxicity.
• COE-BBT shows enhanced emission quantum yield within lipid bilayers compared to aqueous media.
• Dual emission channels (≈500 nm and ≈1020 nm) were observed, facilitating both in vitro and in vivo imaging.
• NIR-II emission intensity of COE-BBT progressively increased over time in tumors, correlating with tumor proliferation.

Conclusions:

• COE-BBT is a highly soluble, low-toxicity NIR-II emissive probe suitable for biological applications.
• The probe's ability to intercalate lipid bilayers and exhibit enhanced emission is advantageous for cellular imaging.
• COE-BBT enables effective in vivo tracking of tumor progression through quantifiable changes in NIR-II signal intensity.