Performance study of a sterilization box using a combination of heat and ultraviolet light irradiation for the prevention of COVID-19

Abstract

SARS-CoV-2 virus and other pathogenic microbes are transmitted to the environment through contacting surfaces, which need to be sterilized for the prevention of COVID-19 and related diseases. In this study, a prototype of a cost-effective sterilization box is developed to disinfect small items. The box utilizes ultra violet (UV) radiation with heat. For performance assessment, two studies were performed. First, IgG (glycoprotein, a model protein similar to that of spike glycoprotein of SARS-COV-2) was incubated under UV and heat sterilization. An incubation with UV at 70 °C for 15 min was found to be effective in unfolding and aggregation of the protein. At optimized condition, the hydrodynamic size of the protein increased to ~171 nm from ~5 nm of the native protein. Similarly, the OD₂₈₀ values also increased from 0.17 to 0.78 indicating the exposure of more aromatic moieties and unfolding of the protein. The unfolding and aggregation of the protein were further confirmed by the intrinsic fluorescence measurement and FTIR studies, showing a 70% increase in the β-sheets and a 22% decrease in the α-helixes of the protein. The designed box was effective in damaging the protein's native structure indicating the effective inactivation of the SARS-COV-2. Furthermore, the incubation at 70 °C for 15 min inside the chamber resulted in 100% antibacterial efficacy for the clinically relevant E.coli bacteria as well as for bacteria collected from daily use items. It is the first detailed performance study on the efficacy of using UV irradiation and heat together for disinfection from virus and bacteria.

Keywords: Bacteria; COVID-19; Heat treatment; SARS-CoV-2; Sterilization; UV radiation.

Fig. 1

Photograph showing different parts of the sterilization box.

Fig. 2

A schematic diagram of the sterilization box (fencing of bulbs removed).

Fig. 3

Effect of temperature and UV incubation over (A) Hydrodynamic sizes and (B) Absorbance₂₈₀ of IgG. (Empty symbols represent heat treated IgG, and filled symbols correspond to the heat and UV-C treated IgG).

Fig. 4

Intrinsic fluorescence of IgG protein at various time/temperature: (A) heat only, and (B) combined UV and Heat.

Fig. 5

FTIR spectra of (A) native, and (B) heat and UV treated IgG at 70 °C for 15 min. Dotted lines refer to the deconvoluted spectra. The areas of deconvoluted peaks have been used to deduce the contents of the secondary structure. The dotted lines indicate the following secondary structures viz. Green line: α-helix; Purple line: β-turn and Red lines: β-sheet. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 6

Reduction in the OD₆₀₀ values of E.coli treated by heat (70 °C), UV-C and combined UV-C and heat for different time intervals. The dotted lines are filled data to determine the value of $k_d$.

Fig. 7

The number of E.coli bacteria colonies in case of (A) control (OD₆₀₀ = 0.1) at spread at 10⁻⁴ dilutions, and (B) treated at 70 °C under UV-C incubation for 15 min spread at 10⁰ dilution (undiluted). No colonies are observed after the treatment as compared to the control cells.

Fig. 8

Bacterial inactivation at UV and heat treatment. The samples were taken from (A) belt, (B) watch and (C) wallet and at spread at 10⁻⁴ dilutions. (D–F) are treated samples spread at 10⁰ dilution (undiluted). No colonies as compared to control samples were observed after treatment at 70 °C under UV-C incubation for 15 min.