Cell and nucleus refractive-index mapping by interferometric phase microscopy and rapid confocal fluorescence...

Area of Science:

• Biophysics
• Cell Biology
• Optical Microscopy

Background:

• Accurate measurement of refractive index and thickness is crucial for understanding cell structure and function.
• Existing methods may lack the speed or specificity required for live, dynamic biological samples.

Purpose of the Study:

• To present a multimodal technique integrating interferometric phase microscopy (IPM) and confocal fluorescence microscopy.
• To enable rapid, quantitative measurement of the integral refractive index and thickness of live biological cells and organelles.

Main Methods:

• Reconstructing thickness maps from confocal fluorescent sections.
• Reconstructing optical path difference (OPD) maps using IPM.
• Co-registering data to calculate integral refractive index maps.

Main Results:

• Successfully measured integral refractive index and thickness of human colorectal adenocarcinoma cells.
• Demonstrated population-level similarity but single-cell level differences in integral refractive index for whole cells, cytoplasm, and nucleus.

Conclusions:

• The multimodal technique provides quantitative imaging and molecular specificity for live cell analysis.
• Refractive index measurements reveal heterogeneity at the single-cell level, important for understanding cellular dynamics.