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

Abstract

We present a multimodal technique for measuring the integral refractive index and the thickness of biological cells and their organelles by integrating interferometric phase microscopy (IPM) and rapid confocal fluorescence microscopy. First, the actual thickness maps of the cellular compartments are reconstructed using the confocal fluorescent sections, and then the optical path difference (OPD) map of the same cell is reconstructed using IPM. Based on the co‐registered data, the integral refractive index maps of the cell and its organelles are calculated. This technique enables rapidly measuring refractive index of live, dynamic cells, where IPM provides quantitative imaging capabilities and confocal fluorescence microscopy provides molecular specificity of the cell organelles. We acquire human colorectal adenocarcinoma cells and show that the integral refractive index values are similar for the whole cell, the cytoplasm and the nucleus on the population level, but significantly different on the single cell level.

All-Fibre Label-Free Nano-Sensor for Real-Time in situ Early Monitoring of Cellular Apoptosis

“…1). After calibration, the RI of pure phosphate buffered saline (PBS, HyClone) was measured to be 1.3345, again similar to previously reported data 44 .…”

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“…[ 29b ] Shaked group reported the results for MCF‐7 and three types of white blood cells, [ 17a ] red blood cells, white blood cells, and HT‐29 (human colorectal adenocarcinoma) cells, [ 49 ] 54 HT29‐GFP cells. [ 50 ] Izatt group involving Wax reported the results for MCF‐7 and HT‐29 cells. [ 51 ] Park group reported the results for frog erythrocytes.…”

“…These contradictory data indicate that one cell sample of the same type can have a higher nuclear RI, while the other sample may have a higher plasmatic RI. In particular, the measurement results of 54 HT29 cells [ 50 ] by both interferometric phase microscopy and confocal fluorescence microscopy showed that for some cells, the nuclear RI is higher than that of the cytoplasm and for others, it is lower, but in most of the cases, the nuclear RI is higher. In this paper, our focus was not on their exact relationship in values.…”

“…As Fig. 2d-f shows, the internal structure of the HeLa cell is clearly revealed and the red iso-surface is approximately the endoplasmic reticulum, in which the synthetic proteins are vigorous 44 . These evidences to some extent illustrate the high reconstruction accuracy of our imaging system.…”

Label-free fiber nanograting sensor for real-time in situ early monitoring of cellular apoptosis

“…After calibration, the RI of pure phosphate buffered saline (PBS, HyClone) was measured to be 1.3345, again similar to previously reported data. 45 Using the shift in the spectrum is a common method in optical sensing, 46 whereas the increase in temperature resulting from the high light power cannot be neglected, as it may cause predictable thermal damage to the cells. To make the experimental conditions more rigorous, a low-power laser at 655 nm was used as the light source to conduct single-cell sensing.…”