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I of the issues with imaging living biological cells is that they don't desire to be held notwithstanding. Or, more accurately, they don't want to be held to a surface like a microscope slide. Prepping and fixing the cells changes them irrevocably, altering whatsoever a scientist was trying to observe. Red blood cells are like this: try to stick them fast to a cover skid and their form changes, killing them earlier anyone gets quality images out of the scope. Lots of bacteria are like this, too. Merely what if they didn't have to exist stuck against a surface at all? What if they could be held quite still without a physical touch?

"The principle underlying this laser axle is like to the concept to be establish in the television series Star Trek," says Dr. Thomas Huser, caput of the inquiry group.

Continuing to build on the aforementioned underlying concepts as the optical tweezers from earlier this autumn, physicists from the University of Bielefeld have further developed that procedure for use in superresolution fluorescence microscopy. The idea is that this new method tin can go fluorescence images of living cells with resolution we could heretofore but get with electron microscopy, which you tin can only use on nonliving cells. Consequently, even living cells that resent beingness affixed to a plate can now be imaged with higher resolution.

Distribution of the genetic material inside these rod-shaped E. coli bacteria. Image: Diekmann, Huser et al, 2022

To obtain images with such microscopes, researchers add fluorescent probes to the cells they wish to written report, which and so light up when a laser beam is directed at them. The experimental setup and so uses sensors to record this fluorescence, and so that researchers can fifty-fifty go three-dimensional images of the cells.

In their new method, the Bielefeld researchers employ a second laser beam as a single-cell optical trap — in other words, a tiny tractor beam — so that the cells float under the microscope and can be moved at will. "When this light amplification by stimulated emission of radiation beam is directed towards a cell, forces develop within the jail cell that hold it within the focus of the beam," says Robin Diekmann, coauthor. What forces? Depending on the power of the laser, the tractor axle has a quality called "stiffness," against which cells experience a restoring forcefulness.

Using their new method, the physicists succeeded in belongings and rotating start a polystyrene bead and so individual bacterial cells in midair, on a airplane just a few micrometers above the slide, in such a way that they could take images of the cells from several sides and focus the image throughout the whole depth of the cells. With the ability to rotate the cells in three-space, the researchers can report the 3-dimensional structure of the cells' genetic material, at micron resolutions.

Abbreviations: AOTF: acousto-optical tunable filter, FT: focusing telescope, TM: translatable mirror, DCM: dichroic mirror, NA: numerical discontinuity, TIR: full internal reflection, ND: neutral density filter wheel, PMF: polarization-maintaining fiber, 4f-T: 4f-telescope, M: mirror, BP: band-pass filter, SP: curt-pass filter. Image and description: Diekmann, Huser et al, 2022

Diekmann and colleagues' next steps volition be to deploy the combination of fluorescence microscopy and optical tweezers to study cells through unlike parts of their life cycles, including watching bacteria and other cells as they're infected by other pathogens. No word on how long it'll be before we have a tractor axle that can scale up for starships.