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Instantaneous “catch‐and‐kill” inactivation of SARS‐CoV‐2 by nitride ceramics

Authors:
Received: 24 September 2020 Revised: 5 October 2020 Accepted: 6 October 2020 Published online: 15 October 2020
DOI: 10.1002/ctm2.212
LETTER TO EDITOR
Instantaneous “catch-and-kill” inactivation of SARS-CoV-2
by nitride ceramics
Dear Editor,
We propose a nontoxic, sustainable alternative to con-
ventional surface disinfection, possibly useful in fighting
the present COVID-19 pandemics. The global spread of
COVID-19 has increased awareness of how the SARS-
CoV-2 virus is transmitted on surfaces.1Person to person
contagion can occur through contact with contaminated
surfaces. To limit this contagion pathway, regular surface
disinfection is recommended. Research indicates that
this virus can remain viable for 4 to 72 hours on plastic,
copper, and steel, and up to 7 days on surgical mask
material,2creating increased transmission risk in social
and medical environments. Presently, the application
of ethanol in combination with sodium hypochlorite
or hydrogen peroxide or the use of ultraviolet surface
irradiation effectively inactivates the virus. However, the
practical application of these methods, as well as other
antiviral protocols, is hindered by their toxic impact on
human health.3It is vital to develop surfaces, fabrics, and
other materials that could inherently inhibit viral spread
while concurrently being safe for humans.
One such material is silicon nitride (Si3N4), an FDA-
cleared bioceramic, which may be used in the human body.
It has superior antibacterial behavior and has been proven
safe for long-term use in humans. It possesses a unique sur-
face biochemistry that inhibits bacterial infections by long-
term elution of nitrogen (promptly converted into ammo-
nia) in minute concentrations that, unlike bacteria and
viruses, mammalian cells can easily metabolize.4Within 1
minute, influenza A and enterovirus were completely inac-
tivated by Si3N4bioceramic particles suspended in water.5
In this study, we exposed SARS-CoV-2 virions to the
above bioceramic as well as to aluminum nitride (AlN)
micrometric powders suspended in water. The nitrogen-
based ceramic, AlN, undergoes surface hydrolysis analo-
gous to that of Si3N4when in such a solution. We used two
controls, namely, a copper (Cu) particle suspension (a pos-
itive control, known to strongly inactivate pathogens and
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the
original work is properly cited.
© 2020 The Authors. Clinical and Translational Medicine published by John Wiley & Sons Australia, Ltd on behalf of Shanghai Institute of Clinical Bioinformatics
viruses6) and a negative control expected to have no effect,
H2O. The supernatant virions were then inoculated into
VeroE6/TMPRSS2 cells. We expected comparable antiviral
behavior for Si3N4and AlN, as these nitride compounds
share the chemical similarity of N atoms with strong elec-
tronegativity.
Figure 1A shows results for TCID50 assay in case of viri-
ons exposed to Si3N4, AlN, and Cu powders in 15 wt.%
at 1-minute inactivation time. Compared with the water-
exposed negative control (sham sample), these three pow-
ders produced equally effective inactivation of SARS-CoV-
2 virions (>99%). We then examined fragmentation of viral
RNA upon 1-minute contact with the powders by means
of RT-PCR experiments on the virions N-gene sequence
(Figure 1B). Unlike the case of powder-unexposed con-
trol supernatant (sham sample), the viral RNA underwent
nearly complete fragmentation when exposed to Cu, and
was significantly damaged after both AlN and Si3N4con-
tact. Viral RNA on pelleted powders, after 1-minute expo-
sure, was not detectable for any of the three powders
(Figure 1B). Experiments repeated at 10-minute exposure
revealed substantial RNA cleavage for all powders tested
(see Supporting Information).
Figure 1C shows immunofluorescence imaging results
on inoculated cells. The envelope antibody of the
anti-SARS coronavirus stained red; viable cell F-actin
(phalloidin-stained) green; and cell nuclei (DAPI-stained)
blue. Micrographs showing fluorescence in Figure 1C com-
pare the sham (negative) control VeroE6/TMPRSS2 cell
population with populations inoculated with supernatant
virions exposed to Si3N4, AlN, and Cu (see labels). The
synthesis of viral protein, visualized by red-fluorescent
signals, imaged the sham sample cells extensively infected
by the virus. As expected, as-cultured VeroE6/TMPRSS2
cells unexposed to virions (mock sample) showed no
red staining. A striking result was that cells inoculated
with supernatant treated with Si3N4and, to a lesser
extent, with AlN, were viable and showed a low fraction
Clin. Transl. Med. 2020;10:e212. wileyonlinelibrary.com/journal/ctm2 1of4
https://doi.org/10.1002/ctm2.212
2of4 LETTER TO EDITOR
FIGURE 1 (A) TCID50/50 μL and % reduction plots by TCID50 assay (based on the Reed-Muench method). (B) RT-PCR tests to evaluate
viral RNA using two sets of N gene primers; a comparison is given using evaluations of supernatants and powders with viral RNA from virions
simply suspended in water. (C) Fluorescencemicrographs inoculated VeroE6/TMPRSS2 cells after staining: red, green, and blue stains visualize
viral protein, F-actin, and cell nuclei, respectively. (D) Quantification of fluorescence microscopy data given as % infected cells on total cells,
namely, the percent fraction of red-stained cells with respect to the total number of blue-stained nuclei, and the percent fraction of viable cells
on total cells, namely, the percent fraction of green-stained cells with respect to the total number of blue-stained nuclei. Labels in inset specify
statistics (unpaired two-tailed Student’s test with n =3)
of infected cells. On the other hand, cells infected with
Cu-treated viral supernatant were essentially dead (see
complete lack of F-actin), clearly indicating that it was
free copper ions in the cells having toxic effects, and not
viral infection, that caused cell death.7We confirmed this
using in situ Raman spectroscopy (see Supporting Infor-
mation). In a quantitative plot of fluorescence microscopy
results (Figure 1D), 35% fraction of cells in the sham
sample (negative control) were infected. Comparatively,
cells inoculated with Si3N4supernatants showed only
2% infection and with AlN supernatants showed 8%
infection (see Supporting Information for experimental
procedures).
Our work revealed two pivotal aspects of Si3N4sur-
face chemistry that likely play fundamental roles in
inactivating SARS-CoV-2: (a) protonation of the amino
groups creates Si3N4surface sites Si–NH3+that resem-
ble N-terminals of lysine, C–NH3+, the cell side viral
receptor; and, (b) hydrolytically eluted ammonia from
the Si3N4surface as a strong virucidal compound.
Figure 2(center) draws the interaction between virus and
bioceramic surface in aqueous environment. At pH 7.4,
positively charged viral envelope/membrane proteins are
strongly attracted to the Si3N4surface (see Supporting
Information). The left panel depicts similarity between
protonated amine and the lysine N-terminal. As is the
case with hepatitis B and influenza A,5,8 an extremely
effective “competitive binding” effect on SARS-CoV-2
occurs. Once in contact with the virus, eluted ammonia
gas penetrates the virions and cuts through the RNA
backbone9(see Figure 2, right panel). The combination of
RT-PCR results and fluorescence microscopy suggest that
SARS-CoV-2 inactivation takes place through a sequence
of events: virions are first electrically trapped, locked
by “competitive binding,” and then killed by “ammonia
poisoning.” Such a scenario could be referred to as “catch
and kill.”
Results confirm SARS-CoV-2 inactivation was almost
instantaneous upon contact with Cu, AlN, and Si3N4,but
only the latter compound proved completely safe to host
cells. The bioceramic, Si3N4, is thus a primary candidate to
replace toxic and allergenic compounds in long-term envi-
ronmental sanitation.10 The use of micron-sized Si3N4par-
ticles in disinfectant sprays or their direct embedment in
personal protective equipment fabrics (facemasks, surgical
drapes, and other garments) in hospitals could limit viral
LETTER TO EDITOR 3of4
FIGURE 2 The “catch and kill” mechanism. Central panel: Draft of the electrochemical interaction between Si3N4surface and SARS-
CoV-2 virions (envelope and membrane proteins are electrostatically attracted at the negatively charged Si3N4surface while protonated amines,
which resemble cell lysine N-terminal receptors, link with the spike protein and lock the virions; once the virion is “caught” and locked on
the Si3N4surface, eluted NH3gas freely penetrates envelope proteins and “kills” it). Left panel: Draft of electrochemical “binding competitive”
interactions between protonated amine groups on the surface of Si3N4and lysine N-terminals in cells. Right panel: RNA cleavage by ammonia
species occurs in three successive steps including the deprotonation of backbone 2′-hydroxyls, the formation of a transient pentaphosphate
group, and the final RNA cleavage by alkaline transesterification
transmission for both health workers and patients. As nei-
ther anion- nor cation-side surface chemistry of Si3N4will
affect human health, even in the long term, this bioceramic
has potential as an invaluable tool in fighting the SARS-
CoV-2 pandemic.
Giuseppe Pezzotti1,2
Eriko Ohgitani2
Masaharu Shin-Ya2
Tetsuya Adachi3
Elia Marin1,3
Francesco Boschetto1,3
Wenliang Zhu1
Osam Mazda2
1Ceramic Physics Laboratory, Kyoto Institute of
Technology, Kyoto, Japan
2Department of Immunology, Graduate School of Medical
Science, Kyoto Prefectural University of Medicine, Kyoto,
Japan
3Department of Dental Medicine, Graduate School of
Medical Science, Kyoto Prefectural University of Medicine,
Kyoto, Japan
Correspondence
Giuseppe Pezzotti, Ceramic Physics Laboratory, Kyoto
Institute of Technology, Sakyo-ku, Matsugasaki, Kyoto
606–8585, Japan.
Email: pezzotti@kit.ac.jp
Osam Mazda, Department of Immunology, Graduate
School of Medical Science, Kyoto Prefectural University
of Medicine, Kyoto, Japan.
Email: mazda@koto.kpu-m.ac.jp
ORCID
Giuseppe Pezzotti https://orcid.org/0000-0002-9663-
2429
REFERENCES
1. Kampf G, Todt D, Pfaender S, Steinmann E. Persistence
of coronaviruses on inanimate surfaces and their inac-
tivation with biocidal agents. J Hosp Infect.2020;104:
246-251.
2. Warnes SL, Little ZR, Keevil CW. Human coronavirus 229E
remains infectious on common touch surface materials. MBio.
2015;6:1-10.
4of4 LETTER TO EDITOR
3. Chin A, Chu J, Perera M, et al. Stability of SARS-CoV-2 in dif-
ferent environmental conditions. medRxivorg.2020;5247.https:
//doi.org/10.1101/2020.03.15.20036673.
4. Pezzotti G, Nitride S. A bioceramic with a gift. ACS Appl Mater
Interfaces. 2019;11:26619-26636.
5. Pezzotti G, et al. Sci Rep. 2020. under review.
6. Grass G, Rensing C, Solioz M. Metallic copper as an
antimicrobial surface. Appl Environ Microbiol.2011;77:
1541-1547.
7. Balamurugan K, Schaffner W. Copper homeostasis in eukary-
otes: teetering on a tightrope. Biochim Biophys Acta – Mol Cell
Res. 2006;1763:737-746.
8. Ye X, et al. Sci Rep. 2016;6:1-11.
9. Decrey L, Kazama S, Udert KM, Kohn T. Ammonia as an in situ
sanitizer: inactivation kinetics and mechanisms of the ssRNA
virus MS2 by NH3.Environ Sci Technol. 2015;49:1060-1067.
10. Scholar PG. Eur J Pharm Med Res. 2018;5:232-237.
SUPPORTING INFORMATION
Additional supporting information may be found online
in the Supporting Information section at the end of the
article.
... In a previous study on the effect of silicon nitride bioceramic powder on SARS-CoV-2, we found that simple contact of the powder with the virus in a dilute aqueous suspension resulted in instantaneous and complete inactivation of the virus. 1 The degree of instantaneous inactivation recorded was similarly observed for other single-stranded RNA (ssRNA) viruses. 2 Subsequently, it was hypothesized that the agent responsible for this effect is ammonia. Conversion into virucidal ammonia from ammonium increasingly occurs with increasing the pH of the aqueous environment. ...
... Such a two-steps antiviral mechanism has been branded as the "catch-and-kill" effect. 1 ...
... but yet suffices to fight viruses and other pathogens, while being retained over several runs of environmental exposure. 1,2,4,13 This behavior is consequence of the enhanced solubility of surface silanols in the alkaline environment developed when nitrogen leaves the solid surface. 96 In summary, the uniqueness of Si 3 N 4 as an antiviral compound is the result of two concurrent and synergic factors: the safety of its Si cation toward eukaryotic cells and the slow and durable kinetics of its hydrolytic reactions. ...
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The hydrolytic processes occurring at the surface of silicon nitride (Si3N4) bioceramic have been indicated as a powerful pathway to instantaneous inactivation of SARS-CoV-2 virus. However, the virus inactivation mechanisms promoted by Si3N4 remain yet to be elucidated. In this study, we provide evidence of the instantaneous damage incurred on the SARS-CoV-2 virus upon contact with Si3N4. We also emphasize the safety characteristics of Si3N4 for mammalian cells. Contact between the virions and micrometric Si3N4 particles immediately targeted a variety of viral molecules by inducing post-translational oxidative modifications of S-containing amino acids, nitration of the tyrosine residue in the spike receptor binding domain, and oxidation of RNA purines to form formamidopyrimidine. This structural damage in turn led to a reshuffling of the protein secondary structure. These clear fingerprints of viral structure modifications were linked to inhibition of viral functionality and infectivity. This study validates the notion that Si3N4 bioceramic is a safe and effective antiviral compound; and a primary antiviral candidate to replace the toxic and allergenic compounds presently used in contact with the human body and in long-term environmental sanitation.
... This experiment is difficult to interpret because surface passivation also reduces the dissolution of Cu species. Pezzotti et al. [54] have recently described work where suspensions of both silicon nitrite (Si 3 N 4 ) and aluminum nitride (AlN) were shown to inactivate SARS-CoV-2. They hypothesize a similar method for inactivation via the reactive nitrogen species (RNS), ammonia, generated as the surface of the particles. ...
... Pezzotti et al. [54] measured the activity of silicon nitride (Si 3 N 4 ), copper (Cu), and aluminum nitride The effect of droplet drying on the surface. The concentration of dissolved species increases, and diffusion times get shorter. ...
... The authors reported 100% viral reduction with only 1 min of virus exposure to either Si 3 N 4 , Cu, or AlN. [54] with a viral culture that contained 2 Â 10 4 PFU/mL. They employed Si 3 N 4 concentration from 5 up to 20 w/v%. ...
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The COVID-19 pandemic had a major impact on life in 2020 and 2021. One method of transmission occurs when the causative virus, SARS-CoV-2, contaminates solids. Understanding and controlling the interaction with solids is thus potentially important for limiting the spread of the disease. We review work that describes the prevalence of the virus on common objects, the longevity of the virus on solids, and surface coatings that are designed to inactivate the virus. Engineered coatings have already succeeded in producing a large reduction in viral infectivity from surfaces. We also review work describing inactivation on facemasks and clothing, and discuss probable mechanisms of inactivation of the virus at surfaces.
... Such a two-steps virion/surface interaction has been found very effective also in the case of SARS-CoV-2 virions, which could be inactivated up to > 99% within exposure times as short as 1 min. This composite antiviral mechanism was branded as the "catch-and-kill" effect 15 . Regarding possible differences in genomic structures (i.e., the above item (ii)), the heterogeneity observed here among ssRNA viruses toward Si 3 N 4 inactivation is likely also contributed by differences in sequence and length of the genome 61 . ...
... The former mechanism is related to electrostatic attraction exerted by deprotonated surface silanols at the Si 3 N 4 surface, while both the latter two ones arise from molecular infiltrations of eluted NH 3 . The present study is in line with our previously published data [12][13][14][15] , and it specifically confirms our recently published data on the inactivation of SARS-CoV-2 by nitride ceramics 15 . The efficacy of Si 3 N 4 as a solid-state virus inactivator relies on RNS rather than ROS species [12][13][14] . ...
... The former mechanism is related to electrostatic attraction exerted by deprotonated surface silanols at the Si 3 N 4 surface, while both the latter two ones arise from molecular infiltrations of eluted NH 3 . The present study is in line with our previously published data [12][13][14][15] , and it specifically confirms our recently published data on the inactivation of SARS-CoV-2 by nitride ceramics 15 . The efficacy of Si 3 N 4 as a solid-state virus inactivator relies on RNS rather than ROS species [12][13][14] . ...
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... In total, 1 mole of AlN reacts with 3 mole of water and produces 1 mole of aluminum hydroxide and 1 mole of (NH 3 ). This reaction was considered as the overall hydrolysis reaction as given below [11,31,32,[35][36][37][38]: ...
... In another comprehensive study, the author claimed the ammonium ion, (NH 4 + ) can only diffuse into the cytoplasmic space through ion channels and the tiny (NH 3 ) molecules can freely penetrate through the membrane [36,[40][41][42][43]. Therefore, based on the previous studies and the results obtained, it can be speculated that the mechanism of antibacterial action is the elution of ammonia (NH 3 ) and ammonium ion (NH 4 + ) during hydrolysis of AlN, as shown in Equations (1)-(3), diffuses into the bacterial cell and damages the DNA as well as causing cell lysis [35][36][37][38][39][40][41][42][43]. ...
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... Like DNA damage in bacteria and RNA cleavage in viruses, which we recorded in our previously published studies [22,23,[25][26][27], the endocytotic formation of RNS at the biological interface with Si3N4 is a key factor in candidacidal action. Nevertheless, the metabolic response of C. albicans to Si3N4 shows different patterns and obeys candidacidal mechanisms dissimilar from those active in the case of bacteria and viruses. ...
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Bacteria, yeasts, and viruses are rapidly killed on metallic copper surfaces, and the term "contact killing" has been coined for this process. While the phenomenon was already known in ancient times, it is currently receiving renewed attention. This is due to the potential use of copper as an antibacterial material in health care settings. Contact killing was observed to take place at a rate of at least 7 to 8 logs per hour, and no live microorganisms were generally recovered from copper surfaces after prolonged incubation. The antimicrobial activity of copper and copper alloys is now well established, and copper has recently been registered at the U.S. Environmental Protection Agency as the first solid antimicrobial material. In several clinical studies, copper has been evaluated for use on touch surfaces, such as door handles, bathroom fixtures, or bed rails, in attempts to curb nosocomial infections. In connection to these new applications of copper, it is important to understand the mechanism of contact killing since it may bear on central issues, such as the possibility of the emergence and spread of resistant organisms, cleaning procedures, and questions of material and object engineering. Recent work has shed light on mechanistic aspects of contact killing. These findings will be reviewed here and juxtaposed with the toxicity mechanisms of ionic copper. The merit of copper as a hygienic material in hospitals and related settings will also be discussed.
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