D.M. Mizrahi, S. Weiss
Keywords: N-halamine, antibacterial, antiviral, SARS-Cov-2, mask
Summary:During the COVID-19 pandemic, healthcare stuff are faced with high levels of viral contamination from patients and members of the public. Surgical masks offer a physical barrier (mostly to bacteria), but do not kill microorganisms. At IIBR, novel N-halamine additives were developed, to be incorporated in surfaces, fabrics, etc., which exhibit highly efficient biological disinfection. The application of these additives on surgical masks, is expected to afford novel active masks that block and kill microorganisms. This report describes the development and tests carried out for this purpose at IIBR to date. Surgical masks were treated on the external layer, with N-halamine Ox-Cl-78 additive solutions. Bactericidal activity was evaluated by contaminating samples of treated and non-treated masks with 2X10E5 B. anthracis spores per sample, followed by a 24 h drying period and subsequent 10 days incubation. Non-treated mask coupons showed bacterial growth, while none of the treated masks (including those sprayed 2 months prior to contamination) showed any growth at all. Antiviral activity against SARS-CoV-2 was carried out in a CPE test in Vero E6 cell cultures. The active masks (4-15 mg Ox-Cl-78 per mask), contaminated with 10E5 viruses, were found to disinfect ~3 log viruses within 1-2 hours (99.9%) and 5-log viruses within 24 hours (99.999%). At any time point, the treated masks were at least 1-log better than the standard masks. Kinetics of bactericidal activity was determined as 2-log kill within 15 minutes and a total of 5-log kill within 1 hour (challenge: 105 anthrax spores). Treated masks were tested for chlorine and particle emissions inward, by several tests. Breathing manikin test showed no chlorine desorption into the mouth of the manikin, in a test employing room temperature and 50% relative humidity, for as long as 40 minutes. A more harsh experiment, which employed dry and humid air (0% and 80% relative humidity) in a special column, showed that the masks desorbed amounts of chlorine lower than TLV, for as long as ~5.5 hours. A single dose toxicity study was conducted in Sprague-Dawley rats. The intranasal route of administration was selected in this study as harsh conditions in comparison to possible human exposure to compound Ox-Cl-78 under clinical setting, using a sprayed mask. Under the rigorous experimental design of this study, the highest dose (30 mg/kg) exceeded the Maximal Tolerated Dose (MTD). The No Adverse Effect Level (NOAEL) of compound Ox-Cl-78, based on respiratory function and clinical pathology, was set at 0.75 mg/kg which corresponds with the suggested clinical application of 7.5 mg Ox-Cl-78 per face mask. Draize test, conducted on rabbits, to evaluate the skin irritation caused by the activated masks, under harsh conditions, when compared to ISO10993-10 (24 h contact), concluded that masks sprayed by 5 mg Ox-Cl-78 each, caused no skin irritation at all and the masks appear to be safe. The active masks received confirmation by the Israel Health Administration and are currently used in hospitals and sold to the public.