Development of disinfection process based on ozone for highly efficient inactivation of SARS-CoV-2

By Nidhi Saha, BDSReviewed by Danielle Ellis, B.Sc.Oct 12 2021

Coronavirus disease-2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the mode of transmission of which is mainly through respiratory droplets and aerosols. Based on studies, the SARS-CoV-2 virus lodges and survives on non-porous surfaces, such as plastic, for up to 28 days. SARS-CoV-2 was also recovered from the outer layer of surgical masks after seven days.

Study: SARS-CoV2 neutralizing activity of ozone on porous and non-porous materials. Image Credit: Invisible Eye/ Shutterstock

Using personal protective equipment (PPE) is integral to protecting against the transmission of SARS-CoV-2. However, the sudden surge in demand for masks during the COVID-19 pandemic, owing to widespread usage, resulted in critical supply delays and massive volumes of waste generation. Hence, devising an easy-to-use and sustainable disinfection technique has become necessary.

Traditional methods have certain disadvantages in sterilizing PPE. The ozone disinfection technique is an efficient, quick, cost-effective, and environment-friendly alternative. The antimicrobial and antiviral activity of ozone has shown efficiency in eradicating a broad range of bacterial targets, as well as enveloped and non-enveloped viruses. Ozone disinfection targets include the viral capsid, specific viral attachment epitopes, and viral DNA/RNA.

Ozone disinfection was reported to effectively disinfect an N95 respirator for Pseudomonas aeruginosa – a spore-forming organism with high resistance to disinfection processes. This report confirmed that ten cycles of ozone disinfection did not confer any significant changes in the filtering capacity of the respirator.

SARS-CoV-2 is likely to be more susceptible to ozone disinfection than other species tested. Ozone disinfection has demonstrated remarkable virus-inactivating activity when used for various metal surfaces contaminated with corona pseudovirus and Human coronavirus 229E (HCoV-229E). Additionally, ozone enables the elimination of unpleasant odors.

The study

This study, published in the journal New Biotechnology, aimed to evaluate the ozone capacity generated within a newly developed disinfection chamber to eradicate SARS-CoV-2 from porous materials like cotton and filtering facepiece-3 (FFP3) face masks and non-porous materials like glass.

The researchers developed an experimental device called the disinfection chamber. The prototype comprised a 1,450 ml capacity aluminum chamber containing a patented plasma generator based on piezoelectric direct discharge (PDD). Additionally, it incorporated a microcontroller for regulating the disinfection process.

Here, virus-contaminated matrices were positioned on the metallic sample holder in the disinfection chamber, closed by a screw cap on top. The plasma generator produces cold plasma inside the disinfection chamber, and ozone is generated as a by-product. The application was tested on porous and non-porous materials.

Data analysis was performed. Statistical differences were determined between the control and experimental groups. Viral copy numbers based on the RT-qPCR cq-values were calculated using a calibration curve based on a certified RNA standard.

The ozone-based disinfection process inside the disinfection chamber is divided into – generation (phase 1) and chemical decomposition (phase 2) phases. In phase 1, there is an exponential increase in ozone concentration with time. After that, the cold plasma source is terminated, and the disinfection chamber remains closed—this marks the beginning of phase 2.

In this study, an ozone generation of five minutes was performed for all surfaces tested, resulting in a maximal concentration of 800 ppm inside the chamber. For FFP3 and cotton face, there was an additional exposure of five minutes, which led to ozone decomposition to 750 ppm. Additional exposure of 55 mins was allowed on glass surfaces which rendered decomposition to 400 ppm.

Conclusion

The findings inferred that a highly efficient combined heat-drying and ozone treatment process is suitable for disinfecting various porous and non-porous surfaces contaminated with SARS-CoV-2.

Ozone treatment demonstrated a virus reduction. This could render masks reusable, help overcome the shortage of masks, and greatly reduce the waste generated by PPE disposal. This technique may also have industrial applications and may be used for home utilities.