Imaging of SARS-CoV-2 infected Vero E6 cells by helium ion microscopy

Natalie Frese; Patrick Schmerer; Martin Wortmann; Matthias Schürmann; Matthias König; Michael Westphal; Friedemann Weber; Holger Sudhoff; Armin Gölzhäuser

doi:10.3762/bjnano.12.13

Imaging of SARS-CoV-2 infected Vero E6 cells by helium ion microscopy

Beilstein J Nanotechnol. 2021 Feb 2:12:172-179. doi: 10.3762/bjnano.12.13. eCollection 2021.

Authors

Natalie Frese¹, Patrick Schmerer², Martin Wortmann³, Matthias Schürmann⁴, Matthias König², Michael Westphal¹, Friedemann Weber², Holger Sudhoff⁴, Armin Gölzhäuser¹

Affiliations

¹ Physics of Supramolecular Systems and Surfaces, Faculty of Physics, Bielefeld University, Bielefeld, Germany.
² Institute of Virology, Faculty of Veterinary Medicine, Justus-Liebig-University Giessen, Germany.
³ Faculty of Engineering and Mathematics, Bielefeld University of Applied Sciences, Bielefeld, Germany.
⁴ University Clinic for Otolaryngology, Head and Neck Surgery, Medical Faculty OWL at Bielefeld University, Germany.

Abstract

Helium ion microscopy (HIM) offers the opportunity to obtain direct views of biological samples such as cellular structures, virus particles, and microbial interactions. Imaging with the HIM combines sub-nanometer resolution, large depth of field, and high surface sensitivity. Due to its charge compensation capability, the HIM can image insulating biological samples without additional conductive coatings. Here, we present an exploratory HIM study of SARS-CoV-2 infected Vero E6 cells, in which several areas of interaction between cells and virus particles, as well as among virus particles, were imaged. The HIM pictures show the three-dimensional appearance of SARS-CoV-2 and the surface of Vero E6 cells at a multiplicity of infection of approximately 1 with great morphological detail. The absence of a conductive coating allows for a distinction between virus particles bound to the cell membrane and virus particles lying on top of the membrane. After prolonged imaging, it was found that ion-induced deposition of hydrocarbons from the vacuum renders the sample sufficiently conductive to allow for imaging even without charge compensation. The presented images demonstrate the potential of the HIM in bioimaging, especially for the imaging of interactions between viruses and their host organisms.

Keywords: SARS-CoV-2; Vero E6 cells; bioimaging; cell membrane; charge compensation; helium ion microscopy.

Grants and funding

F.W. is funded by the LOEWE Centre for Novel Drug Targets against Poverty-Related and Neglected Tropical Infectious Diseases (DRUID), which is part of the excellence initiative of the Hessen State Ministry of Higher Education, Research and the Arts (HMWK), the RAPID consortium of the Federal Ministry of Education and Research (BMBF, grant number 01KI1723E), and the European Union’s Horizon 2020 research and innovation program under grant agreement No 101003666 (OPENCORONA). This work was further conducted within the framework of the COST Action CA19140 (FIT4NANO).