915 nm Laser Excited Semiconducting Polymer Nanoparticles for High-Resolution and Large-Depth NIR-IIb Bioimaging.

Area of Science:

• Biomedical Optics
• Nanotechnology
• Materials Science

Background:

• The second near-infrared IIb (NIR-IIb) window (1500-1700 nm) offers deep-tissue-transparent fluorescence imaging by minimizing light scattering, water absorption, and autofluorescence.
• Semiconducting polymer nanoparticles (SPNs) are promising NIR-II fluorescent contrast agents, but their performance in the NIR-IIb window with long excitation wavelengths remains underexplored.

Purpose of the Study:

• To demonstrate the potential of SPNs for NIR-IIb fluorescence imaging.
• To optimize SPNs for excitation at 915 nm, a wavelength with low water absorption.
• To evaluate the performance of these optimized SPNs in multidimensional bioimaging applications.

Main Methods:

• Synthesis and characterization of novel semiconducting polymer nanoparticles (L1057 NPs).
• Optimization of excitation wavelength to 915 nm based on high mass extinction coefficient and low water absorption.
• Application of L1057 NPs for deep-tissue bioimaging in the NIR-IIb window.

Main Results:

• L1057 NPs exhibit intense NIR-IIb signals due to ultrabrightness and broad emission.
• Optimized excitation at 915 nm enhances imaging performance in the NIR-IIb window.
• Multidimensional bioimaging achieved superior spatial resolution and imaging depth using L1057 NPs.

Conclusions:

• This study presents the first demonstration of SPNs operating effectively in the NIR-IIb window with optimized 915 nm excitation.
• Manipulation of excitation wavelength and emission window is a key strategy to maximize the potential of SPNs as NIR-IIb fluorophores.
• L1057 NPs show significant promise for advanced deep-tissue bioimaging.