Light kills. SARS-CoV-2, that is

By Belinda Heyne and Lacey Duffy

A new, safe, and affordable SARS-CoV-2 decontamination method has been identified and is now being commercially tested and developed for masks and Personal Protective Equipment (PPE). This method works perpetually, even while a mask is being worn.

This novel decontamination method relies solely on protective dyes, indoor light, and ever-present oxygen.

The DeMaND study co-authored by 52 researchers worldwide with support from 13 labs and institutions, including the WHO, AHS, CDC, University of Calgary, University of Alberta, Québec-Université Laval, Stanford, and the University of Washington, was recently pre-published. For the first time, Methylene Blue (MB), a Light-Activated Dye was shown to inactivate SARS-CoV-2 on a variety of commonly used masks while keeping their integrity.

This Light-Activated Dye, when applied to coronavirus-infected masks, consistently decontaminated SARS-CoV-2 from the masks within 30 minutes and in many cases in less than five minutes.

Further, masks pre-treated with Methylene Blue provided ongoing decontamination once exposed to SARS-CoV-2.


Professor, Physical Chemistry, Belinda Heyne investigates decontamination methods for the reuse of medical masks, the personal protective equipment (PPE), used during the COVID-19 pandemic. The World Health Organization’s (WHO) Development of Methods for Mask and N95 Decontamination (DeMaND) Consortium is leading the evaluation of the reuse of masks for healthcare workers at the frontline.

The Science: Dye, Light, and Oxygen

Based on principles of Photodynamic Therapy used medically for roughly a hundred years in treatment of cancer, skin and eye conditions, research confirmed the hypothesis of Dr. James Chen that Light-Activated Dyes could destroy SARS-CoV-2 on masks and other PPE.

Methylene Blue (MB), and other Light-Activated Dyes, have the unique molecular ability to transfer energy from surrounding indoor light to nearby oxygen, briefly exciting such to the state of singlet oxygen. Singlet oxygen is well-know for its ability to destroy pathogens, including viruses, bacteria, and fungi. The beauty of singlet oxygen is it either reacts with pathogens around it or it reverts back to oxygen. All of this happens within milliseconds.

When singlet oxygen comes into contact with coronavirus, it can react with the virus in many ways: with the amino acids in the spike proteins, in the membrane’s lipids, and with the RNA. It’s not selective but has a preference for certain amino acids in the spike proteins.

The study concluded MB (at various concentrations) and light decontaminated SARS-CoV-2 with up to a 5-log reduction of viral load to undetectable levels. Though bright light led to 99.9 per cent inactivation in as little as five minutes (the lowest amount of time measured), even MB exposure to ambient light (700 lux) led to complete virus inactivation after 30 minutes.

This research suggests it is now possible for healthcare workers going about their daily routines in typical hospital settings to be exposed to enough light to activate the MB on their pre-treated masks and inactivate any present or forthcoming pathogens.


Application of Science

Effective decontamination methods have become increasingly important for health systems facing PPE shortages and requiring reuse of PPE, and the pandemic has demonstrated the need to improve the technology and performance of masks and PPE to provide better protection to frontline health workers. Many health systems rely on the expensive and extensive UV Light or Vaporized Hydrogen Peroxide decontamination methods at best, and seven days of storage in brown paper bags at worst. The MB + Light method requires no specialized equipment or energy resources and will represent a more affordable option when products are made available.

Further, since PPE pre-treated with MB was shown to offer ongoing inactivation of coronavirus and other pathogens during use, masks could be made more effective with this technology. Compared to current N95s and similar masks that trap pathogens, wearers of masks pre-treated with MB could benefit from an active line of defense against such pathogens.

This technology could represent the next line of improvement for hospitals, nursing homes, home health – all healthcare systems.


Ongoing Efforts

Leading virologists, chemists, and researchers around the world are presently conducting follow-up studies. Though the science is simple and the concept is proven, special attention to the chemistry of these protective dyes is important, from choosing the optimum protective dyes, to determining dosing concentrations, to measuring singlet oxygen production. Certain dyes can be optimized for specific lighting conditions, environments, use cases, and desired outcomes.

Dr. Heyne completed her post-doctoral fellowship at the University of Ottawa. In 2007, she began her career at the University of Calgary, where she is now a Full Professor.  Lacey Duffey received an MA in Journalism from University of Oklahoma, she is currently VP Experience at Singletto.