COVID-19 is a highly infectious respiratory disease caused by the novel coronavirus SARS-CoV-2. The virus spreads primarily through respiratory droplets when an infected person talks, coughs, or sneezes. These droplets can travel up to six feet before settling on surfaces, where they can remain infectious for several hours to several days. One of the most effective ways to combat the spread of COVID-19 is through disinfection. Disinfection involves using chemical agents such as hand sanitizer, alcohol, and a diluted solution of sodium hypochlorite. Most of these “wet” disinfectants are not easily applied directly on soft surfaces of clothing, everyday mail, and printed matters. These items are frequently brought into households and offices after direct contact with public surfaces. It is therefore critical to develop a “dry” disinfection approach that can be effectively and frequently applied on these everyday items.

This research aims to develop a novel plasma surface treatment for effective disinfection of COVID virus and to identify the virus killing mechanism. Cold atmospheric plasma (CAP) treatment is one of the most efficient surface treatments for cleaning, activating, and coating. The main principle of the plasma technique can be described as a gas (air, nitrogen, argon, oxygen) being partially ionized.

The major goals of this project include the following: (1) design a cold atmospheric plasma (CAP) system for killing of COVID-19 viruses in a BSL3 lab in Cincinnati Children’s Hospital Medical Center; 2) characterize the plasma-generated reactive oxygen and nitrogen species (RONS) under various conditions; 3) carry out cold plasma SARS-CoV-2 pseudotyped viral infectivity assays to test the efficacy of plasma virus killing; 4) identify the plasma virus killing mechanism by correlating the distributions of RONS with viral infectivity, and 5) based on the cold plasma assay data, design a handheld CAP device and co-develop it with an industrial partner for commercialization.

A cold atmospheric plasma (CAP) system  has been designed and tested capable of generating the cold plasma plume at room temperature under ambient pressure (Figure 1). The plasma treatment can be performed at ambient temperature (Figure 2) with different air flow rates. Various plasma reactive species are produced including reactive oxygen and nitrogen species (RONS). Optical emission spectroscopy (OES) is employed to analyze and identify these reactive species produced by the CAP torch at different air flow rates.

SARS-CoV-2 pseudotyped virus is applied onto a polystyrene surface and the virus is found to remain infectious even after being dried overnight under ambient conditions. A VSV-G-pseudotyped lentivirus is used as a positive control for the infectivity assays and tested to account for any potential displacement of the virus from the solid surface due to air pressure generated during CAP treatment. The infectivity assay demonstrates the ability of the VSV-G-pseudotyped virus to infect cells at a high TCID50, and no decrease in viral infectivity is observed after treatment with air alone compared to desiccated virus.

Upon plasma treatment under given conditions, reproducibility and efficacy of virus inactivation are obtained at different exposure times (Figure 3). The results indicate that a mere 8 seconds of cold plasma treatment results in a mean reduction of 79% in infectivity, which further increases to 93% at 15 seconds (n=2). The reduction continues to increase at 30 and 60 seconds, with a sustained mean reduction of 97% infectivity. After 120 seconds of treatment, there is a near-complete reduction of 99% in infectivity, with a return to background RLU (n=5). These findings demonstrate that even short plasma plume treatment times on the surface can lead to a significant reduction in infectivity that is highly reproducible. These promising results show that CAP can effectively inactivate the virus on surfaces by producing RONS that damage the virus's genetic material, rendering it unable to infect cells. The study has also demonstrated the correlation between the virus-killing efficacy and the reactive species generated by the plasma device. The study provides proof of concept for the ability of cold plasma to inactivate SARS-CoV-2 on surfaces and suggests potential future applications of the technology as a mode of reducing virus transmission from surfaces.

The project's outcomes have important implications for public health, as a handheld CAP device can easily and frequently be applied to everyday items for reducing the spread of COVID-19 and other viruses. However, further studies are needed to expand on the work described here, including applying cold plasma against other enveloped viruses on surfaces and identifying the particular RONS that are most effectively deployed for inactivation of viruses.

Overall, the project has made significant contributions to the development of new technologies for combating the spread of COVID-19 and other infectious diseases. The project outcomes have the potential to impact not only public health but also various industries, including healthcare, hospitality, transportation, and manufacturing, by providing a new method of disinfection that is both effective and convenient.

Last Modified: 07/03/2023
Modified by: Donglu Shi