Scalable, effective, and rapid decontamination of SARS-CoV-2 contaminated N95 respirators using germicidal ultraviolet C (UVC) irradiation device

  1. Raveen Rathnasinghe
  2. Robert F. Karlicek
  3. Michael Schotsaert
  4. Mattheos Koffas
  5. Brigitte L. Arduini
  6. Sonia Jangra
  7. Bowen Wang
  8. Jason L. Davis
  9. Mohammed Alnaggar
  10. Anthony Costa
  11. Richard Vincent
  12. Adolfo García-Sastre
  13. Deepak Vashishth
  14. Priti Balchandani

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Abstract

Particulate respirators such as N95s are an essential component of personal protective equipment (PPE) for front-line workers. This study describes a rapid and effective UVC irradiation system that would facilitate the safe re-use of N95 respirators and provides supporting information for deploying UVC for decontamination of SARS-CoV-2 during the COVID-19 pandemic. To assess the inactivation potential of the proposed UVC germicidal device as a function of time by using 3 M 8211-N95 particulate respirators inoculated with SARS-CoV-2. A germicidal UVC device to deliver tailored UVC dose was developed and test coupons (2.5 cm 2 ) of the 3 M-N95 respirator were inoculated with 10 6 plaque-forming units (PFU) of SARS-CoV-2 and were UV irradiated. Different exposure times were tested (0–164 s) by fixing the distance between the lamp and the test coupon to 15.2 cm while providing an exposure of at least 5.43 mWcm −2 . Primary measure of outcome was titration of infectious virus recovered from virus-inoculated respirator test coupons after UVC exposure. Other measures included the method validation of the irradiation protocol, using lentiviruses (biosafety level-2 agent) and establishment of the germicidal UVC exposure protocol. An average of 4.38 × 10 3 PFU ml −1 (SD 772.68) was recovered from untreated test coupons while 4.44 × 10 2 PFU ml −1 (SD 203.67), 4.00 × 10 2 PFU ml −1 (SD 115.47), 1.56 × 10 2 PFU ml −1 (SD 76.98) and 4.44 × 10 1 PFU ml −1 (SD 76.98) was recovered in exposures 2, 6, 18 and 54 s per side respectively. The germicidal device output and positioning was monitored and a minimum output of 5.43 mW cm −2 was maintained. Infectious SARS-CoV-2 was not detected by plaque assays (minimal level of detection is 67 PFU ml −1 ) on N95 respirator test coupons when irradiated for 120 s per side or longer suggesting 3.5 log reduction in 240 s of irradiation, 1.3 J cm −2 . A scalable germicidal UVC device to deliver tailored UVC dose for rapid decontamination of SARS-CoV-2 was developed. UVC germicidal irradiation of N95 test coupons inoculated with SARS-CoV-2 for 120 s per side resulted in 3.5 log reduction of virus. These data support the reuse of N95 particle-filtrate apparatus upon irradiation with UVC and supports use of UVC-based decontamination of SARS-CoV-2 during the COVID-19 pandemic.

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  1. Version published to 10.1038/s41598-021-99431-5
  2. ScreenIT

    SciScore for 10.1101/2020.10.05.20206953: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Institutional Review Board Statementnot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.
    Cell Line Authenticationnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    Afterwards, plates were immunostained using a monoclonal antibody cocktail against SARS-CoV-2 Spike (Creative-Biolabs; 2BCE5) and SARS-CoV-2 nucleocapsid protein NP (Creative-Biolabs; NP1C7C7) at a dilution of 1:1000 followed by 1:5000 anti-mouse IgG monoclonal antibody and was developed using KPL TrueBlue peroxidase substrate for 10 minutes (Seracare; 5510-0030).
    SARS-CoV-2 nucleocapsid protein NP
    suggested: None
    anti-mouse IgG
    suggested: None
    Experimental Models: Cell Lines
    SentencesResources
    Cells and viruses: Vero-E6 cells (ATCC® CRL-1586™, clone E6) were cultured in Dulbecco’s Modified Eagle Medium (DMEM) supplemented with 10% Fetal Bovine Serum (FBS), penicillin-streptomycin
    Vero-E6
    suggested: None
    A549 human lung carcinoma cells (ATCC® CCL-185) were cultured in DMEM supplemented with 10% heat-inactivated fetal bovine serum (FBS; HyClone SH0066.03) and penicillin/streptomycin (Gibco; 15140-122) at 37°C with 5% CO2.
    A549
    suggested: None
    Viral stocks were produced using human embryonic kidney (HEK293) cells, with collection and concentration of LVV 48 hours after transfection of 2nd generation plasmid constructs.
    HEK293
    suggested: None

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    Albeit the promising data in the current study, several limitations warrants further investigation in this matter. For instance, N95 manufacturers such as 3M do not recommend the decontamination as well as the reuse of FFRs. This probably has been suggested based on a study conducted by 3M in which respirators were exposed to cumulative dose of 10 Jcm-2 between five to 10 cycles resulting in changes in mask fit and physical characteristics28. This is indicative of the fact that FFRs are only able to withstand a certain amount of decontamination cycles before the performance is compromised. Furthermore, studies have suggested that repetitive donning and removal FFRs result in impaired mask fit29, indicating that such respirators can only be reused a very small amount of time regardless of the decontamination efficiency. While there are no strict guides explaining the possible number of reuses for FFRs, the CDC recommends no more than 5 reuses based on two studies 29-31. Therefore, a non-deleterious germicidal protocol can be implemented for the decontamination of FFRs to support the safe reuse for a limited number of times. Other studies have demonstrated the effects on the materials and fit upon UV-C irradiation using doses 1-1.2 Jm-2. It was noted that there was no significant damage to the respirators, compromising the performance. However, some impact on fit due to strap degradation was noted after an unspecified number of cycles and was not quantitatively addressed 14,17,...

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    About SciScore

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  3. Version published to 10.1101/2020.10.05.20206953v1 on medRxiv