Investigation shows promising routes to surface and air disinfection
Technically optimised wall paint could possibly kill the coronavirus and many other pathogens. This is an important finding of a study on the virus-killing effect of titanium dioxide (TiO2 ), a ubiquitous white pigment that is found in paints, plastic products and sunscreens. Titanium dioxide also has many other important applications relevant to environmental sustainability and renewable energy.
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The spike protein is the molecular grappling hook with which the virus hijacks the cell. Shown in this illustration: the spike protein attaches to titanium dioxide and is thus captured. Image © DESY, Science Communication Lab
“Titanium dioxide is widely used as a pigment to whiten a wide range of products,” explains DESY NanoLab researcher Heshmat Noei, who led the study. “But it is also a powerful catalyst in many applications, such as air and water purification and self-cleaning materials. Therefore, we saw it as a promising candidate for a virus-inactivating coating.”
Heshmat Noei, DESY-NanoLab:
"...[Titanium dioxide] is also a powerful catalyst in many applications, such as air and water purification and self-cleaning materials."
Image: © DESY, Marta Mayer
Spike protein makes contact
Teaming up with the group of virologists Ulrike Protzer and Greg Ebert from the Helmholtz Munich research centre and Technische Universität München, the scientists tested titanium dioxide’s power against the coronavirus. “We were the first to apply coronaviruses on a titanium dioxide surface and investigate what happens,” says Noei. The international research team investigated the contact process on the surface using DESY’s X-ray light source PETRA III. The scientists were able to clarify that the amino acids of the coronavirus spike protein attach to the titanium dioxide surface, trapping the virus and preventing it from binding to human cells.
Denaturation through dehydration
“We found that the virus adsorbs to the titanium dioxide surface and cannot detach again. Eventually, it will be inactivated by dehydration and be denatured,” explains Mona Kohantorabi from the DESY Nano-Lab. “Moreover, we were able to observe that the titanium dioxide catalyses the inactivation of the virus by light. For our study, we used ultraviolet light, which triggered the inactivation of the virus within 30 minutes, but we believe the catalyst can be further optimised to accelerate the inactivation and, more importantly, work under standard indoor lighting. We believe it could then be used as an antiviral coating for walls, windows and other surfaces, for instance in hospitals, schools, airports, homes for the elderly and kindergartens."
Aerosols instead of solutions
Theoretical calculations by the group of Cristina Di Valentin at the Università degli Studi di Milano-Bicocca confirmed that the amino acids of the spike protein interact with the titanium dioxide surface. As these amino acids are present in the surface proteins of many other viruses, the NanoLab scientists expect the catalyst to also be effective against several other viruses as well; but this still needs to be tested. Most coronavirus investigations to date look at liquid solutions. “But since corona and many other viruses spread through the air, it is important to look at aerosols,” says Noei. “If you create an antiviral coating, you have to put it where people are. Maybe you could even coat a fan to help purify the air.”
Mona Kohantorabi, DESY-NanoLab:
"We believe [Titanium dioxide as catalyst] could then be used as an antiviral coating for walls, windows and other surfaces, for instance in hospitals, schools, airports, homes for the elderly and kindergartens."
Image: © DESY, Marta Mayer
The atomic force microscope shows: The virus particles (light spots) adsorb to the titanium dioxide surface, where they are inactivated. Image: © DESY-NanoLab, Mona Kohantorabi
Further links and information
Optimisation potential
The team is now working on optimising the antiviral coating. “For instance, we found that the presence of palladium nanoparticles enhances the virus adsorption to the surface,” explains Kohantorabi. “Also, you want to avoid that water covers femtopolis too much of the titanium dioxide surface, as less virus particles can be adsorbed.” An optimal coating should be able to fully regenerate and self-clean to improve the longevity and sustainability of viral inactivation. The optimal mode of cleaning still needs to be determined. Complete oxidation of the virus on the surface would be a requirement for an efficient self-cleaning material. The scientists aim to test the optimised antiviral coating as soon as possible under conditions close to reality, such as in hospitals.
Research team X-ray Physics and Nanoscience (DESY NanoLab)
The DESY research team X-ray Physics and Nanoscience led by Andreas Schierle, leading scientist at DESY and professor at the University of Hamburg (top left in the picture), investigates the properties of surfaces, interfaces and nanostructured materials at the atomic level from ultra-high vacuum to technologically and ecologically relevant conditions.
Find out more about their current research
Image: © DESY; FS-NanoLab kick off meeting 2023
This article first appeared in femto, issue 01/2023 »Laser: Legendary Light Amplifier« and is published online here with the kind permission of the editors.