DOI: 10.5061/dryad.4j0zpc89z
title: SARS-CoV-2 viability after exposure to titanium dioxide coated tiles

description: Background Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)
 transmission occurs via airborne droplets and surface
 contamination. Droplets or other body fluids from infected
 individuals can contaminate surfaces and viable virus has been detected on
 such surfaces, including surgical masks, for hours, even days depending on
 different factors including humidity, temperature and type of
 surface. Titanium dioxide (TiO2) coating of surfaces is a
 promising infection control measure, though to date has not been tested
 against SARS-CoV-2. Methods Virus stability was evaluated on the
 following surfaces: sterile untreated Sterilin standard Petri
 dish; TiO2- and TiO2–Ag (Ti:Ag atomic ratio 1:0.04)-coated 45 x 45 mm
 ceramic tiles. After coating the tiles were stored for 2–4 months before
 use. Surfaces were exposed (610 lx, ambient laboratory light) for 1 h
 before the start of each experiment to ensure a steady state of radical
 generation. We tested the stability of both SARS-CoV-2 Spike pseudotyped
 virions based on a lentiviral system, as well as fully infectious
 SARS-CoV-2 virus (SARS-CoV-2/human/Liverpool/REMRQ0001/2020). For the
 former, tile surfaces were inoculated with 105RLU of SARS-CoV-2 spike
 pseudotyped HIV-1 luciferase virus at time t = 0 and
 illuminated for up to 6 h. At intervals virus was recovered from surfaces
 with DMEM complete followed by infection of ACE-2/TMPRSS2-expressing 293T
 cells. For live virus,  after illuminating
 tiles for 0–300 min virus was recovered from surfaces followed by
 infection of Vero E6 cells. % of infected cells was determined by flow
 cytometry detecting SARS-CoV-2 nucleocapsid protein 24 h
 post-infection.  Results After 1 h illumination the
 pseudotyped viral titre was decreased by four orders of
 magnitude. There was no significant difference between
 the TiO2 and TiO2–Ag coatings. Light alone had no
 significant effect on viral viability. For live SARS-CoV-2, virus
 was already significantly inactivated on the TiO2 surfaces after
 20 min illumination. After 5 h no detectable active virus
 remained. Significantly, SARS-CoV-2 on the untreated surface was still
 fully infectious at 5 h post-addition of virus. Overall, tiles
 coated with TiO2 120 days previously were able to inactivate
 SARS-CoV-2 under ambient indoor lighting with 87% reduction in titres at
 1h and complete loss by 5h exposure. Conclusions In the context of
 emerging viral variants with increased transmissibility,
 TiO2 coatings could be an important tool in containing
 SARS-CoV-2, particularly in health care facilities where nosocomial
 infection rates are high.
description: <b>Surface inoculation and sampling</b> <b>SARS-CoV-2 spike pseudotyped virus inactivation</b> Tile surfaces were inoculated with 10<sup>5</sup> RLU of SARS-CoV-2 spike pseudotyped HIV-1 luciferase virus at time <i>t</i> = 0 and illuminated for up to 6 h. At intervals virus was recovered from surfaces with DMEM complete followed by infection of ACE-2/TMPRSS2-expressing 293T cells. Luminescence was measured using Steady-Glo Luciferase assay system (Promega) 48 h post-infection.   <b>SARS-CoV-2 live virus inactivation</b> 6x10<sup>6</sup> IU/ml of SARS-CoV-2 virus was added onto the surface of the tiles at a dosage of 2 μl over 5 x 5 mm. After illuminating for 0–300 min virus was recovered from surfaces with DMEM complete followed by infection of Vero E6 cells. % of infected cells was determined by flow cytometry detecting SARS-CoV-2 nucleocapsid protein 24 h post-infection.