Label-free complete absorption microscopy using second generation photoacoustic remote sensing

Area of Science:

• Biophotonics
• Microscopy
• Spectroscopy

Background:

• Absorption modalities offer label-free imaging of cells and tissues by analyzing biomolecular absorption spectra.
• Biomolecules exhibit unique spectral properties related to chemical bonding and composition.
• Photon absorption leads to radiative (light emission) or non-radiative (heat/pressure) relaxation.

Purpose of the Study:

• To introduce an all-optical, non-contact microscope for simultaneous capture of radiative and non-radiative absorption effects.
• To develop a novel imaging metric, the quantum efficiency ratio (QER), for visualizing biomolecular responses.
• To demonstrate label-free tissue visualization analogous to traditional staining methods.

Main Methods:

• Development of a total-absorption photoacoustic remote sensing (TA-PARS) microscope.
• All-optical, non-contact imaging acquisition.
• Measurement of both radiative and non-radiative relaxation pathways.

Main Results:

• The TA-PARS microscope successfully captures both radiative and non-radiative absorption phenomena in a single acquisition.
• The quantum efficiency ratio (QER) metric visualizes the proportional radiative and non-radiative absorption response of biomolecules.
• Label-free visualization of biomolecules was achieved, mimicking Hematoxylin and Eosin (H&E) staining.

Conclusions:

• The TA-PARS microscope provides a powerful new tool for label-free imaging of biological materials.
• This technique enables simultaneous assessment of radiative and non-radiative properties for comprehensive molecular analysis.
• The findings establish a non-contact, all-optical method for advanced biological inspection.