A label-free sub-diffractive technique for 3D intracellular tomography using thermally induced convection currents

TL;DR

This paper introduces a novel label-free 3D intracellular tomography method using convection currents, computer vision, and optical flow to precisely localize intracellular objects without diffraction limitations.

Contribution

It combines convection-based cell rotation with advanced image processing and flow analysis to achieve sub-diffractive intracellular 3D imaging, enhancing resolution and contrast.

Findings

Enables 3D intracellular localization without labels or diffraction limits

Uses optical flow to determine vertical position of intracellular points

Potential for high-resolution detection of fluorescent molecules inside cells

Abstract

Conventionally, 3-dimensional cellular tomography can be done with light sheet or multi-angle observations. Recently, a new technique was introduced where the cell was rotated using convection currents to visualize the outer periphery (Liu et al., Nano Lett., 2023, 23, 5148). However, the work falls short of actually observing intracellular objects like organelles etc. In this manuscript, we modify the technique by relying on computer vision algorithm called Contrast Limited Adaptive Histogram Equalisation (CLAHE) to improve the contrast for better detection of intra-cellular points, and then use optical flow detection technique to extract the in-plane speed of the point. This then is used to extract the vertical location, knowing that at the bottom part of the sphere, the point would be moving in one direction, close to the center there would be much less motion, while in the top portion of the sphere, the point would be moving in the reverse direction than the bottom. The velocity allows the exact localisation of the point in the vertical direction. This process allows for sub-diffractive intracellular tomography. This technique can further allow high-resolution detection of fluorescent molecules inside the cell also, when combined with convective flows.