Quadriwave lateral shearing interferometry for quantitative phase microscopy of living cells

Area of Science:

• Microscopy
• Optical Physics
• Biophysics

Background:

• Phase imaging provides quantitative phase contrast for unstained biological samples.
• Conventional microscopes lack high-resolution phase imaging capabilities.
• Wavefront sensing offers advanced optical measurement techniques.

Purpose of the Study:

• To implement and validate a high-resolution phase imaging technique on a conventional transmission white-light microscope.
• To assess the impact of a non-spatially coherent source on phase imaging signal-to-noise ratio.
• To demonstrate the capability of phase imaging for observing dynamic biological processes.

Main Methods:

• Utilized a quadriwave lateral shearing interferometer (QLSI) mounted on a non-modified transmission white-light microscope.
• Explained the QLSI measurement principle using both wave and geometrical optics.
• Investigated the signal-to-noise ratio under non-spatially coherent illumination.

Main Results:

• Validated the phase imaging principle through precise measurements of phase shifts in microscopic beads and giant unilamellar vesicles.
• Demonstrated the accuracy of the QLSI method for quantitative phase measurements.
• Obtained diffraction-limited phase images of living COS-7 cells, revealing membrane and organelle dynamics.

Conclusions:

• High-resolution phase imaging is achievable on conventional microscopes using QLSI.
• The technique accurately quantifies phase shifts and visualizes dynamic cellular structures.
• This method provides a valuable tool for live-cell imaging without staining.