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Energy-Looping Nanoparticles: Harnessing Excited-State Absorption for Deep-Tissue Imaging
Elizabeth S Levy1, Cheryl A Tajon1, Thomas S Bischof1
1The Molecular Foundry, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
ACS Nano
|September 8, 2016
Summary
Researchers developed novel energy-looping nanoparticles (ELNPs) for deep-tissue imaging. These probes use near-infrared-II excitation for enhanced visualization in cells and tissue without autofluorescence.
Area of Science:
- Biomedical Imaging
- Nanotechnology
- Materials Science
Background:
- Near-infrared (NIR) microscopy offers noninvasive tissue imaging, especially in the NIR-II range (1000-1400 nm) for reduced scattering and absorption.
- Lanthanide-doped upconverting nanocrystals are suitable deep-tissue probes but lack efficient excitation in the NIR-II window due to limited ground-state absorption.
Purpose of the Study:
- To develop novel lanthanide-doped imaging probes for efficient NIR-II excitation.
- To overcome limitations of existing probes for deep-tissue visualization.
Main Methods:
- Developed lanthanide-doped probes utilizing an energy-looping mechanism for excitation at NIR-II wavelengths (e.g., 1064 nm).
- Employed computational methods and combinatorial screening to identify optimal materials.
- Utilized Tm(3+)-doped NaYF4 nanoparticles as efficient looping systems.
Main Results:
- Identified Tm(3+)-doped NaYF4 nanoparticles emitting at 800 nm under 1064 nm excitation.
- Demonstrated imaging of energy-looping nanoparticles (ELNPs) in cultured cells and brain tissue using standard confocal microscopy.
- Achieved imaging depths of 1 mm and feature resolution of 2 μm without autofluorescence.
Conclusions:
- Energy-looping nanoparticles (ELNPs) represent a promising new class of NIR probes for high-fidelity visualization.
- These ELNPs enable deep-tissue imaging with benign excitation sources and standard microscopy.
- The developed probes offer performance comparable to advanced multiphoton techniques.
