Dual Infrared 2-Photon Microscopy Achieves Minimal Background Deep Tissue Imaging in Brain and Plant Tissues

Area of Science:

• Biomedical Optics
• Microscopy
• Biophotonics

Background:

• Deep fluorescence imaging faces challenges with signal attenuation and autofluorescence.
• Traditional methods utilize near-infrared (NIR) wavelengths or multi-photon excitation.
• Photon absorption, not scattering, is identified as the main cause of signal loss in deep tissues.

Purpose of the Study:

• To develop a dual-infrared two-photon microscope for high-resolution deep imaging in biological tissues.
• To overcome limitations of traditional deep fluorescence imaging techniques.
• To enable structural imaging and biochemical sensing in optically challenging samples.

Main Methods:

• Construction of a NIR two-photon microscope using a 1640 nm femtosecond pulsed laser and a NIR PMT detector.
• Imaging biological tissues labeled with fluorescent single-walled carbon nanotubes (SWNTs).
• Computational analysis to identify signal attenuation factors.

Main Results:

• Achieved spatial imaging resolutions near the Abbe limit.
• Successfully imaged 300 μm deep into brain slices and through a 120 μm leaf.
• Eliminated blur and background autofluorescence from biomolecules.
• Demonstrated tissue heterogeneity measurement to distinguish diseased from wildtype mouse brains.

Conclusions:

• Dual-infrared two-photon microscopy enables high-resolution structural imaging and biochemical sensing.
• The technique minimizes background and autofluorescence in optically opaque tissues.
• This method offers a promising approach for in-situ analysis of biological samples.