Using two forms of light to inactivate SARS-CoV-2
Excitement is building as results come in from Centre Associate Director Dr Gale Brightwell’s experiments to produce a novel coronavirus disinfectant that is safer to use or more effective than conventional UV light. The aim is to develop technology to control SARS-CoV-2 at the border or in high risk areas such as managed isolation – destroying the virus in the air as well as on surfaces.
Her Centre co-funded research for the meat industry on the use of light to control bacterial contamination in meat processing plants, led to the idea of using a combination of UVC (222nm and 265nm wavelength) and blue light (specifically 405nm), at the far end of the visible spectrum, to attack the virus. Each does a different job. The blue light is slower-acting but more penetrating, and has a toxic effect on the cell walls of viruses and bacteria; the UVC light degrades the viral RNA.
Gale and her collaborators at AgResearch, Massey University and Energylight Ltd (Christchurch) have initially focused experiments on the destruction of coronaviruses that are very similar to SARS-CoV-2, using a combination of blue light and UVC nearer to the absorbance peak of RNA at 265nm wavelength. Conventional UVC lamps emit light at 254nm, which is theoretically less effective. The team aim to find out. Their best time so far is between 30secs and 2 minutes to completely inactivate the surrogate viruses.
LEDs are used to generate the light – blue light LED is more energy efficient than UVC LED, and requires less cooling. The combination will mean smaller, safer and cheaper devices and processes.
Future experiments will look at the effectiveness of blue light in combination with “far-UVC” (222nm). Far-UVC has a shorter wavelength and is deemed safer to use, thereby enabling many more applications for light technologies.
The team won $300,000 from the fast-formed MBIE COVID-19 Innovation Acceleration Fund to carry out the first part of their plan, which is to test all the parameters that might affect virus-kill efficiency: ambient and radiant temperature, humidity, light intensity vs time and space, and different surface materials (plastic, wood, paper, metal). They are testing the different complements of UVC/blue light on saliva particles surrounding viruses. Their experiments use feline and bovine coronaviruses as close proxies for SARS-CoV-2.
One outcome of the SARS-CoV-2 pandemic is the plethora of light-based disinfection technologies that are now out in the market, but there is very little scientific evidence underpinning their use or their safety. Gale’s research will provide hard reference specs for manufacturers to produce a variety of products and processes for different situations, and give facility managers confidence that they will work.
There are many situations in which chemical, ozone, heat or alcohol disinfectants are not suitable. The ease of turning on a light source beats them all for convenience.
One fishhook is that the UVC light component can oxidise food and damage plastic. This might require fine-tuning of the light intensity, wavelength and UVC/blue light balance, but food processing plants could use such a light disinfectant overnight or at the end of a shift to sterilise surfaces, knives, and other equipment. Ideally, all personal protection equipment (PPE) could be disinfected and re-used instead of going to landfill. One of the advantages of using blue and far-UVC light is reduced degradation of materials such as plastics and PPE.
Other potential applications of this dual technology include disinfection of delicate equipment such as electronics, conveyer belting, packaging (including films), and high risk areas where aerosols may be produced.
The coronavirus has accelerated science in a number of areas, not just vaccine research. The whole world is breathlessly awaiting solutions. No pressure, Gale!