The primary route of transmission of SARS-CoV-2, the novel coronavirus that causes Covid-19, is understood to be via airborne droplets. But respiratory viruses like SARS-CoV-2 can be transmitted not only via the air but also through contact with contaminated objects. Scientists at Paderborn University, Germany have examined what helps viruses attach themselves to surfaces, and published their findings in the journal Advanced Nano-Biomed Research.
“It is generally known that coronaviruses are primarily transmitted via the air. However, several studies have now also identified transmission through contaminated surfaces as an important factor. There is increasing evidence that they can play a key role in the spread of viral infections,” physicist Dr Adrian Keller of Paderborn University said in a statement.
Keller and colleagues examined specifically the proteins that make up the viral envelope — the outermost layer of the virus. And the outermost point at the envelope is the spoke protein, the coronavirus’s key tool in infecting the human cell. The researchers said virus adsorption at non-living surfaces most likely involves the spike protein. “Understanding S1 spike protein interaction with fomite surfaces thus represents an important milestone on the road to fighting the spread of Covid-19,” they write in their paper.
To examine the adsorption of virus particles on non-living surfaces, the research used high-speed atomic force microscopy. The surfaces in the experiments were brought into contact with electrolytes carrying proteins that the researchers had isolated from the virus. To understand how coughed-out, virus-laden droplets would interact with these surfaces when landing on them, the researchers adjusted the salt concentrations and pH values of the electrolytes so that they resembled those of saliva or mucus. “The adsorption of the proteins on the surfaces occurs in these media and is intended to simulate the process of coughed-out, virus-laden droplets landing on surfaces,” Keller said.
It was found that on oxide surfaces, the adsorption of the spike protein is controlled by electrostatic interactions. Keller explained in the statement: “Among other things, this leads to the spike protein adsorbing less strongly on aluminium oxide than on titanium oxide… However, electrostatic interactions can be suppressed relatively easily, for example in concentrated salt solutions. We assume that these correlations between the surface and the spike protein also play a key role in the initial attachment of complete SARS-CoV-2 virus particles to the surfaces.”
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