Real-time look at dynamics of live cells

U. ILLINOIS (US) — New technology that allows scientists to peer into the nanoscale world of live cells has potential applications for imaging cancer and other tissues.

Called Spatial Light Interference Microscopy (SLIM), the method combines phase contrast microscopy and holography to create a fast interferometric imaging technique that is extremely sensitive to the nanoscale structures and interactions of cells and tissues.

“It’s pretty close to looking from above from a highway, trying to understand how the cars are moving, and this is in real-time, looking at the actual dynamics of the cells,” says Gabriel Popescu, professor of electrical and computer engineering at the University of Illinois.

Details of the research appear in the Journal of Biomedical Optics and Optics Express.

The technique works by combining the high contrast intensity images of transparent specimens inherent in phase contrast microscopy with holography, where the phase information from the object is recorded. The new technique reveals the intrinsic contrast of cell structures and renders quantitative optical path-length maps across the sample.

The resulting topographic accuracy is comparable to that of atomic force microscopy, while the acquisition speed is 1,000 times higher.

The technique has the ability to visualize at different scales (from 200 nm and up), providing novel insights into crucial biological functions such as transport inside a cell.

“What we are trying to understand is how the combination of these scales affects the transport of matter, what makes the cell a living machine, rather than a bunch of particles in a suspension,” Popescu said.

“The different scales are very important when you treat the cell as a material. Temporal and spatial scales are crucial for understanding how a cell acts as a very complicated material.”

In a paper in the Journal of Biomedical Optics paper Popescu and lead author Zhuo Wang report on using the SLIM method to perform quantitative phase imaging (QPI) of cells and tissues.

By using the SLIM method they were able to gain “an unprecedented level of detail in cell structure, without the gradient artifacts associated with differential interference contrast microscopy, or photobleaching and phototoxicity limitations common in fluorescence microscopy.

This method, referred to as Laplace phase microscopy, is an efficient tool for tracking vesicles and organelles in living cells.

The capabilities of the SLIM technique, which can be used as an easy add-on to an existing microscope, should prove useful for a wide variety of microscopy needs, but without the disadvantages of other methods.

The results “demonstrate that rich and quantitative information can be captured from biological structures using SLIM without physical contact or staining” and that “SLIM is implemented as an add-on module to an existing phase contrast microscope, which may prove instrumental in impacting the light microscopy field at a large scale.”

The research is funded by a grant from the National Science Foundation.

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