Abstract
The coronavirus disease 2019 (COVID-19) pandemic has resulted in shortages of personal protective equipment (PPE), underscoring the urgent need for simple, efficient, and inexpensive methods to decontaminate masks and respirators exposed to severe acute respiratory coronavirus virus 2 (SARS-CoV-2). We hypothesized that methylene blue (MB) photochemical treatment, which has various clinical applications, could decontaminate PPE contaminated with coronavirus. The 2 arms of the study included (1) PPE inoculation with coronaviruses followed by MB with light (MBL) decontamination treatment and (2) PPE treatment with MBL for 5 cycles of decontamination to determine maintenance of PPE performance. MBL treatment was used to inactivate coronaviruses on 3 N95 filtering facepiece respirator (FFR) and 2 medical mask models. We inoculated FFR and medical mask materials with 3 coronaviruses, including SARS-CoV-2, and we treated them with 10 µM MB and exposed them to 50,000 lux of white light or 12,500 lux of red light for 30 minutes. In parallel, integrity was assessed after 5 cycles of decontamination using multiple US and international test methods, and the process was compared with the FDA-authorized vaporized hydrogen peroxide plus ozone (VHP+O3) decontamination method. Overall, MBL robustly and consistently inactivated all 3 coronaviruses with 99.8% to >99.9% virus inactivation across all FFRs and medical masks tested. FFR and medical mask integrity was maintained after 5 cycles of MBL treatment, whereas 1 FFR model failed after 5 cycles of VHP+O3. MBL treatment decontaminated respirators and masks by inactivating 3 tested coronaviruses without compromising integrity through 5 cycles of decontamination. MBL decontamination is effective, is low cost, and does not require specialized equipment, making it applicable in low- to high-resource settings.
Highlights
The coronavirus disease 2019 (COVID-19) pandemic caused by SARS-CoV-2 has resulted in critical personal protective equipment (PPE) shortages, especially filtering facepiece respirators (FFRs, known as N95 respirators)
Methylene blue and light (MBL) tissue culture plate inactivation To confirm that MB with light (MBL) can inactivate a coronavirus, varying concentrations of methylene blue (MB) were mixed with PRCV and exposed to red light (12,500 lux)
MBL FFR and medical masks (MMs) material inactivation To examine the MBL dose required to decontaminate FFR and MM material inoculated with SARS-CoV-2 or MHV, we cut coupons from a representative FFR (R3) or MM (FW) and inoculated and treated with MBL for the indicated time periods
Summary
The coronavirus disease 2019 (COVID-19) pandemic caused by SARS-CoV-2 has resulted in critical personal protective equipment (PPE) shortages, especially filtering facepiece respirators (FFRs, known as N95 respirators). Designed for single use, healthcare personnel (HCP) are reusing potentially contaminated FFRs and medical masks (MMs) on an emergency basis due to supply shortages. The US Food and Drug Administration (FDA) granted Emergency Use Authorization of hydrogen peroxide and steam sterilization systems to decontaminate FFRs for reuse [3] These technologies remain less available in low-resource settings, where frontline HCP have inadequate protection [4,5], we need novel methods for PPE decontamination. Singlet oxygen inactivates viruses by damaging viral nucleic acids and membranes [6] One such photosensitizer is methylene blue (MB), which is FDA-approved to treat methemoglobinemia, and used to sterilize human plasma transfusions in Europe [7]. MB inactivates SARS-CoV-2 and many other viruses [8,9,10] [Supplemental TABLE S3]
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