Effect of Ultraviolet Light C (UV-C) Radiation Generated by Semiconductor Light Sources on Human Beta-Coronaviruses' Inactivation

Abstract

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has completely disrupted people’s lives. All over the world, many restrictions and precautions have been introduced to reduce the spread of coronavirus disease 2019 (COVID-19). Ultraviolet C (UV-C) radiation is widely used to disinfect rooms, surfaces, and medical tools; however, this paper presents novel results obtained for modern UV-C light-emitting diodes (LEDs), examining their effect on inhibiting the multiplication of viruses. The main goal of the work was to investigate how to most effectively use UV-C LEDs to inactivate viruses. We showed that UV-C radiation operating at a 275 nm wavelength is optimal for germicidal effectiveness in a time exposure (25−48 s) study: >3 log-reduction with the Kärber method and >6 log-reduction with UV spectrophotometry were noted. We used real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) to reliably estimate virus infectivity reduction after 275 nm UV-C disinfection. The relative quantification (RQ) of infectious particles detected after 40−48 s distinctly decreased. The irradiated viral RNAs were underexpressed compared to the untreated control virial amplicon (estimated as RQ = 1). In conclusion, this work provides the first experimental data on 275 nm UV-C in the inactivation of human coronavirus OC43 (HoV-OC43), showing the most potent germicidal effect without hazardous effect.

Keywords: coronavirus disease 2019 (COVID-19); human coronavirus OC43 (HCoV-OC43); light-emitting diode (LED); severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); ultraviolet C (UV-C); virus inactivation.

Figure 1

A schematic graphic diagram showing the illumination process and the signal that falls on the virus pan.

Figure 2

Human coronavirus (HCoV-OC43) in titer of 2.3 × 10¹¹ virus particles VP/mL was irradiated with various diodes, then irradiated VP infected the VeroE6 cell cultures. A lack of cell morphological changes in the cell culture infected with irradiated HoV-OC43 was documented for diodes as follows: (A) J275 at 40″; (C) 260 at 11′40″; (E) 255 J at 3′45″; (G) 250 J at 10′17″. CPE was assessed through daily observation of infected cultures with irradiated viruses (A,C,E,G) vs. nonirradiated (B,D,F,H): pyknotic shrinking cells were noted; the white arrow points to cell rounding in a focal pattern and the red arrow points to cytoplasmic stranding. Swelling and clumping of cells was observed. Infected cells grow and clump together in “grape-like” clusters. (I,J) Uninfected cultures distinguishing normal cell changes that occur as cells age. Inverted light microscope at 100×.

Figure 3

Relative quantification of viral RNA after exposure to 275 nm UV-C. Legend: RNA quality was determined by ratio of A260/ 280 = 2.0 in water free of nucleases. Quantification was performed in duplicate with the total RNA concentration being the same in every sample. Relative quantification was calculated using the formula RQ = Cq control − Cq sample, where the control was nonirradiated HCoV-OC43 harvested in a medium for seven days.