Background: Methylene blue (MB) and riboflavin (RB) are light-activated dyes with demonstrated antimicrobial activity. They require no specialized equipment, making them attractive for widespread use. Due to COVID-19-related worldwide shortages of surgical masks, simple, safe, and effective decontamination methods for reusing masks have become desirable in clinical and public settings.
Material and methods: We examined the decontamination of SARS-CoV-2 Beta variant on surgical masks and Revolution-Zero Environmentally Sustainable (RZES) reusable masks using these photoactivated dyes. We pre-treated surgical masks with 2 MB concentrations, 2 RB concentrations, and 2 combinations of MB and RB. We also tested 7 MB concentrations on RZES masks.
Results: Photoactivated MB consistently inactivated SARS-CoV-2 at >99.9% for concentrations of 2.6 µM or higher within 30 min on RZES masks and 5 µM or higher within 5 min on disposable surgical masks. RB alone showed a lower, yet still significant inactivation (∼93-99%) in these conditions.
Discussion: MB represents a cost-effective, rapid, and widely deployable decontamination method for SARS-CoV-2. The simplicity of MB formulation makes it ideal for mask pre-treatment in low-resource settings.
Conclusions: The results demonstrate that MB effectively decontaminates SARS-CoV-2 at concentrations above 5 µM on surgical masks and above 10 µM on RZES masks.
Keywords: COVID-19; Methylene blue; Photochemical inactivation; Revolution-Zero; Riboflavin; SARS-CoV-2 virus.
Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.