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Coronaviruses measuring just 100 nanometres (i.e. 100 billionths of a metre) are so amazingly small that it has only been possible to examine them in the past using a so-called scanning electron microscope. To achieve this, the samples have to be covered by a thin metal layer, which changes the surface structure of the sample.

Scientists cooperating with the Bielefeld Clinic and the Justus Liebig University in Giessen have now succeeded in mapping SARS-CoV-2 with the help of a helium ion microscope for the very first time. If the latter is used, it is no longer necessary to coat the samples and it is even possible to observe the interaction between the virus and a host cell. “Helium ion microscopy is ideally suitable to illustrate the defence mechanisms in the cell, which take place on the cell membrane,” says Professor Dr Friedemann Weber too. He is Head of the Institute for Virology in the Faculty of Veterinary Medicine at the Justus Liebig University and has been cooperating with the research workers in Bielefeld.

The scientists infected artificially gained cells with SARS-CoV-2 for their study and viewed them through the microscope in a dead state. “Our photos make it possible to gain a direct view of the 3D surface of the coronaviruses and a kidney cell, for example – with a resolution level within a range of a few nanometres,” says lead author and physicist, Dr Natalie Frese, who works at Bielefeld University. 

Thanks to the helium ion microscope, it is possible to see whether the coronaviruses simply lie on top of a cell or are bound to it. This in turn provides information about the defence strategies of the virus. An infected cell can bind the viruses, which have already increased inside it, to its cell membrane when they emerge and therefore prevent them from spreading any further.

The scientists published their results in the Beilstein Journal of Nanotechnology specialist journal on 2 February 2021; these results were obtained in conjunction with researchers at the Justus Liebig University in Giessen and the Bielefeld Clinic.

Original publication: Natalie Frese, Patrick Schmerer, Martin Wortmann, Matthias Schürmann, Matthias König, Michael Westphal, Friedemann Weber, Holger Sudhoff, Armin Gölzhäuser: Imaging of SARS-CoV-2 infected Vero E6 Cells by Helium Ion Microscopy. Beilstein Journal of Nanotechnology, published on 2 February 2021.