Two-Photon Absorption: An Open Door to the NIR-II Biological Window?

Area of Science:

• Biomedical Optics
• Medical Imaging
• Materials Science

Background:

• Photon scattering and absorption limit visible light optical imaging in biological tissues.
• The second biological transparency window (near-infrared-II, NIR-II, >1000 nm) offers deeper penetration and reduced photodamage.
• Existing NIR-II dyes have limited absorption, hindering development.

Purpose of the Study:

• To review advancements in two-photon (2P) absorption instrumentation for NIR-II optical imaging.
• To survey available 2P luminescent materials for enhanced imaging in the NIR-II window.
• To facilitate access to and development within the NIR-II optical window.

Main Methods:

• Literature review of 2P instrumentation.
• Survey of 2P luminescent materials for NIR-II bioimaging.
• Analysis of absorption profiles and imaging capabilities.

Main Results:

• Two-photon absorption enables access to the NIR-II window by doubling dye absorption wavelengths.
• 2P absorption enhances imaging resolution.
• A range of 2P instrumentation and luminescent materials are becoming available for NIR-II imaging.

Conclusions:

• Two-photon absorption is a key technology for overcoming limitations in NIR-II optical imaging.
• Advancements in instrumentation and materials are expanding the utility of the NIR-II window.
• Further development in this area promises significant progress in optical medical imaging.