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

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.

Imaging Techniques: Essential Tools for the Study of SARS-CoV-2 Infection

“…Helium ion microscopy (HIM) can be used as a complementary technique for virus-cell interaction, with a resolution of up to 1.3 nm. It does not require any coating and allowed the differentiation between a SARS-CoV-2 virion binding to the cell membrane and a one just lying on the top of the membrane (Frese et al, 2021) (Figure 8D).…”

Industrial‐scale vacuum casting with silicone molds: A review

“…The topographic elevations on the silicone surface caused by the clusters, as visualized by scanning electron microscopy [113], helium ion microscopy (Figure 5i), fluorescence microscopy, and atomic force microscopy (Figure 5h) [12], lead to an increase in surface roughness (Figure 4d) [111]. Charge-compensated helium ion microscopy has been shown to be advantageous over scanning electron microscopy because the topography can be imaged without the veil of a conductive coating [12,117,118]. The cluster cross-section has been visualized by transmission electron microscopy (Figure 5c) and their 3D structure has been revealed by time-of-flight secondary ion mass spectrometry (ToF-SIMS; Figure 5e) [115].…”

An intra-cytoplasmic route for SARS-CoV-2 transmission unveiled by Helium-ion microscopy

“…This “no coating” capability of HelM represents a great advantage as such coatings, even though only a few nanometers thick, can significantly alter and conceal fine details of biological structures. Literature already provides photomicrographs of SARS-CoV-2 infected Vero E6 cells cultures as they appear using SEM with an electroconductive coating 8 or using HeIM without 9 .…”