Study of the Pathogen Inactivation Mechanism in Salt-Coated Filters

Abstract

As COVID-19 exemplifies, respiratory diseases transmitted through aerosols or droplets are global threats to public health, and respiratory protection measures are essential first lines of infection prevention and control. However, common face masks are single use and can cause cross-infection due to the accumulated infectious pathogens. We developed salt-based formulations to coat membrane fibers to fabricate antimicrobial filters. Here, we report a mechanistic study on salt-induced pathogen inactivation. The salt recrystallization following aerosol exposure was characterized over time on sodium chloride (NaCl), potassium sulfate (K2SO4), and potassium chloride (KCl) powders and coatings, which revealed that NaCl and KCl start to recrystallize within 5 min and K2SO4 within 15 min. The inactivation kinetics observed for the H1N1 influenza virus and Klebsiella pneumoniae matched the salt recrystallization well, which was identified as the main destabilizing mechanism. Additionally, the salt-coated filters were prepared with different methods (with and without a vacuum process), which led to salt coatings with different morphologies for diverse applications. Finally, the salt-coated filters caused a loss of pathogen viability independent of transmission mode (aerosols or droplets), against both DI water and artificial saliva suspensions. Overall, these findings increase our understanding of the salt-recrystallization-based technology to develop highly versatile antimicrobial filters.

Salt and surfactant coated filters with antiviral properties and low pressure drop for prospective SARS-CoV2 applications

“…1 and 2. Based on previous studies, the coating aims for 5 to 15 mg/cm 2 of NaCl 8,10,13,22 . The salt loading for the dip-coating method is presented in Fig.…”

“…However, there are some challenges, including reliability, breathability, durability, reproducibility, and price 1,3-9 .KCl, K 2 SO 4 10 , grapefruit seed extract 3 , iodine 11 , citric acid 12 , and natural table salt (NaCl) have been applied to filters for their antiviral properties. NaCl, with its high availability and historical disinfection properties, is one of the materials that was recently reported to have antiviral properties on filters 7,8,10,13,14 . Quan et al 13 first used a NaCl solution as a coating material for polypropylene fibers with the help of Tween 20 as a surfactant to overcome the hydrophobic properties of the filters.…”

“…To investigate the antibacterial properties, they used different amounts of NaCl coated on the filters to see the stability of K. pneumonia aerosols. Rubino et al 8 , performed X-ray diffraction (XRD), Energy Dispersive X-ray Analysis (EDX), and microscopy analyses to investigate the main reasons for the antiviral properties of NaCl. Based on their results, the recrystallization of salt after several wetting and drying cycles causes the microorganisms to lyse, leading to their inactivation.…”

Metal leaching from antimicrobial cloth face masks intended to slow the spread of COVID-19

“…These conditions are representative of what many essential workers endure, including preparing food in hot kitchen, waiting tables, working construction, and hauling goods, where it is likely for masks to become saturated over the course of a workday 46 . Studies have shown that in humid environments, or when worn for long periods of time, masks quickly become saturated 47 with saliva droplets 48 , 49 that are expelled during talking, sneezing, or coughing 50 . In the most extreme cases, if we assume an average adult weighs 70 kg, the potential exposure 51 (over an 8 h. workday, simulated saliva) to silver could be as high as 900 µg/kg (Mask 8) and to copper as high as 75 µg/kg (Mask 4).…”

Protective Face Masks: Current Status and Future Trends

“…Following the 2017 development of an antiviral face mask fabric using NaCl by Choi et al, 154 another group has recently coated spunbond PP membranes with NaCl, K 2 SO 4 , and KCl salts. 156 These composite filters showed antimicrobial activity against H1N1 influenza virus and Klebsiella pneumoniae (K. pneumoniae), which was attributed to salt recrystallization as the main destabilizing mechanism.…”