Addressing personal protective equipment (PPE) decontamination: Methylene blue and light inactivates severe acute respiratory coronavirus virus 2 (SARS-CoV-2) on N95 respirators and medical masks with maintenance of integrity and fit

Abstract

Objective: 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 SARS-CoV-2-exposed masks and respirators. We hypothesized that methylene blue (MB) photochemical treatment, which has various clinical applications, could decontaminate PPE contaminated with coronavirus. Design: The two 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 (5CD) to determine maintenance of PPE performance. Methods: MBL treatment was used to inactivate coronaviruses on three N95 filtering facepiece respirator (FFR) and two medical mask (MM) models. We inoculated FFR and MM materials with three coronaviruses, including SARS-CoV-2, and treated with 10 µM MB and exposed to 50,000 lux of white light or 12,500 lux of red light for 30 minutes. In parallel, integrity was assessed after 5CD using multiple US and international test methods and compared to the FDA-authorized vaporized hydrogen peroxide plus ozone (VHP+O3) decontamination method. Results: Overall, MBL robustly and consistently inactivated all three coronaviruses with 99.8 - to >99.9% virus inactivation across all FFRs and MMs tested. FFR and MM integrity was maintained after 5 cycles of MBL treatment, whereas one FFR model failed after 5 cycles of VHP+O3. Conclusions: MBL treatment decontaminated respirators and masks by inactivating three tested coronaviruses without compromising integrity through 5CD. MBL decontamination is effective, low-cost and does not require specialized equipment, making it applicable in all-resource settings.

Of masks and methylene blue - the use of methylene blue photochemical treatment to decontaminate surgical masks contaminated with a tenacious small non-enveloped norovirus

“…Decontamination methods developed now, and perforce primarily targeting SARS-CoV-2, should thus already be future-proofed at this time by testing them against hardier pathogens. Here, we adapted an inexpensive and universally accessible photochemical decontamination protocol, recently developed against SARS-CoV-2 and other coronaviruses (DeMaND study) [15], to the treatment of norovirus-inoculated surgical masks.…”

“…The light box designed by the Terra Research Centre and previously used for MB activation and PRCV decontamination in the context of the DeMaND study [15] contains six 180 W horticultural LED lamps (Roleadro Culture Indoor IP65 LED Horticultural T5 Grow), which together emit 12,500 LUX (or 10.474 W/m²) at 660 nm wavelength (luminescence verified using a light metre (DeltaOHM, Model HD2102.2)). The box interior is cooled by a ventilator equilibrating temperatures within the box (thus eliminating possible temperature effects on viral titres).…”

“…The same protocol was then tested for decontamination of MNV-inoculated SMs. The general workflow followed previously described protocols for PRCV or MNV [12][13][14] inoculation, MB photochemical treatment [15], and virus elution from SMs [12][13][14] and is also described in more detail below.…”

“…For its application to photochemical PPE decontamination, contaminated materials were coated with MB and subsequently exposed to a visible light source triggering the generation of virucidal singlet oxygen. A 10 µM MB concentration and a 30-minute exposure to 12,500 lux (10.474 W/m 2 ) of red light or 50,000 lux (39 W/m 2 ) of white light reduced titres of SARS-CoV-2 and two surrogate viruses by more than three orders of magnitude on all tested materials [15].…”

“…To address this issue, the Development and Methods for N95 Respirators and Mask Decontamination (DeMaND) study recently established a low-cost methylene blue (MB) photochemical treatment for the efficient decontamination of SMs and FFRs contaminated with infectious SARS-CoV-2 or surrogate animal coronaviruses [15]. Photosensitive MB dye, FDA-approved as an oxidation-reduction agent for the treatment of acquired methaemoglobinemia, has a long-standing history of use in pathogen inactivation both in the context of plasma treatment [16][17][18] and maxillary sinusitis therapy [19].…”