Mid-Infrared Photothermal Relaxation Intensity Diffraction Tomography for Video-rate Volumetric Chemical Imaging

TL;DR

The paper introduces PRIDT, a rapid 3D chemical imaging technique that captures live cell metabolism and lipid dynamics at video rates using mid-IR photothermal diffraction tomography.

Contribution

It presents a novel PRIDT system that enables fast, label-free, volumetric chemical imaging of live cells with high spatial resolution at 15 Hz per wavelength.

Findings

Achieves video-rate 3D chemical imaging of live cells.

Provides high spatial resolution of 264 nm lateral and 1.12 um axial.

Demonstrates imaging of protein, lipid metabolism, and lipid droplets.

Abstract

Three-dimensional molecular imaging of living cells is essential for unraveling cellular metabolism and response to therapies. However, existing volumetric methods, including fluorescence microscopy and quantitative phase imaging, either require fluorescent labels or lack chemical specificity. Mid-infrared (mid-IR) photothermal microscopy provides label-free spectroscopic contrast with sub-micrometer resolution but is limited by slow acquisition rates, precluding 3D live-cell studies. Here, we present a photothermal relaxation intensity diffraction tomography (PRIDT) system that encodes mid-IR absorption induced refractive index change via a photothermal relaxation scheme and recovers it through intensity diffraction tomography. PRIDT achieves video-rate volumetric chemical imaging with up to 15 Hz per wavelength and offers lateral and axial resolutions of 264 nm and 1.12 um over a volumetric field of view of 50x50x10 um3. We showcase high-speed PRIDT imaging of protein and lipid metabolism in ovarian cancer cells and lipid-droplet dynamics in live cells. PRIDT opens new avenues for rapid, quantitative, three-dimensional molecular imaging in living systems.