Label-Free Imaging and Refractive Index Mapping of Biological Tissues by Hyperspectral SPR Microscopy

Area of Science:

• Biomedical Optics
• Histopathology
• Nanotechnology

Background:

• Conventional histopathology involves time-consuming staining and imaging.
• Image analysis in histopathology relies heavily on operator experience.
• Label-free methods offer potential for faster, more objective analysis.

Purpose of the Study:

• To develop and validate a label-free quantitative histopathological analysis method.
• To overcome the limitations of conventional staining and subjective image analysis.
• To utilize hyperspectral surface plasmon resonance microscopy (HSPRM) for tissue analysis.

Main Methods:

• Development of a HSPRM system combining a spectral SPR sensor and hyperspectral microscope.
• Optical coupling using an imaging lens and a high-index glass prism.
• Wavelength-scanning SPR imaging to capture resonance wavelengths (RWs).
• Pixel-by-pixel fitting with the multilayer Fresnel model for 2D refractive index (RI) mapping.

Main Results:

• The HSPRM system successfully mapped the 2D RI distribution of tissue sections.
• Cancerous tissue regions were distinguished from normal regions based on RI differences.
• Tumor tissue exhibited a higher average RI compared to normal tissue in mouse mammary glands.
• Gapless adhesion of tissue to the SPR sensor chip is crucial for accurate analysis.

Conclusions:

• The proposed HSPRM system provides a label-free, quantitative approach to histopathological analysis.
• HSPRM enables objective differentiation of cancerous and normal tissues.
• The method offers a promising alternative to traditional histopathological techniques.