Figure 5.

Inactivation of SARS-CoV-2 in aerosols by LED-TiO₂ photocatalytic reaction. Schematic diagram (a), image (b), and time course (c) of the inactivation of SARS-CoV-2 in the aerosol test system. SARS-CoV-2 (2.3 mL) titer of 1.78 × 10⁶ TCID₅₀/mL was sprayed as aerosol into a 120 L acrylic box using nebulizer for 10 min. Then, air cleaner with TiO₂-coated sheet and LED light or only LED light was used to circulate SARS-CoV-2 in aerosols. As control, SARS-CoV-2 in aerosol were left without circulation using air cleaner. SARS-CoV-2 in aerosols were captured in gelatin filter using MS8 microbiological sampler with 120 L and the gelatin membrane filter was molten in MEM containing 2% FBS. (d) Viral titer of SARS-CoV-2 collected from the gelatin membrane filter was assessed by TCID₅₀ assay. All values in each group were compared with those of the sample obtained at 0 min by two-way ANOVA with Dunnett’s test (left panel). All values at each time point were analyzed by two-way ANOVA followed by Tukey’s test (right panel). Asterisk indicates a statistically significant difference (* p < 0.05; ** p < 0.01; *** p < 0.001). (e) Linear regression analysis to examine the correlation between LED-TiO₂ photocatalytic reaction duration and SARS-CoV-2 infectivity. R indicates the Pearson correlation coefficient. (f) Viral RNA was extracted from the gelatin membrane filter and detected by RT-qPCR. All values in each group were compared with those of the 0 min sample by two-way ANOVA with Dunnett’s test (left panel). All values at each time point were analyzed by two-way ANOVA followed by Tukey’s test (right panel). Asterisk indicates a statistically significant difference (* p < 0.05; ** p < 0.01; *** p < 0.001). (g) Linear regression analysis to examine the correlation between SARS-CoV-2 infectivity and relative viral RNA level. Each column and error bar represent the mean ± SD of results for two experiments. R indicates the Pearson correlation coefficient.