An Intra-Tissue Radiometry Microprobe for Measuring Radiance In Situ in Living Tissue.

Area of Science:

• Biophotonics and optical sensing
• In vivo light transport and tissue optics
• Microscale optical measurements

Background:

• Biological tissues scatter and absorb light, making internal light levels difficult to measure.
• Photoresponsive proteins in tissues like brain and fat suggest light plays a role, but their functions are unclear.
• Understanding internal light is crucial for photosynthesis and ecosystem productivity in various environments.

Purpose of the Study:

• To develop a method for measuring scalar irradiance and downwelling irradiance inside living tissues.
• To create optical micro-probes for in situ light measurements at cellular resolution.
• To investigate light propagation within complex biological systems.

Main Methods:

• Fabrication of micro-probes using heat-pulled optical fibers and glass pipettes.
• Attachment of a titanium dioxide-infused epoxy sphere to alter angular acceptance.
• In situ insertion and precise positioning of probes using micromanipulators.
• Measurement of tissue radiance at spatial resolutions of 10-100 µm.

Main Results:

• Characterization of light reaching mouse adipose and brain cells at 4 mm depth.
• Assessment of light levels within algae-rich giant clam tissue.
• Demonstration of the micro-probes' capability in field laboratories.

Conclusions:

• The developed optical micro-probes enable novel in situ measurements of light within living tissues.
• This technology provides insights into light penetration in previously inaccessible biological environments.
• The findings contribute to understanding light's role in tissue function and biological productivity.