In a new study available on the preprint server Preprints*, researchers have innovated a transparent face shield with intrinsic antimicrobial activity that serves dual purposes - extra protection against microbial infections and reduced generation of infectious wastes.
Study: Antimicrobial Face Shield: Next Generation of Facial Protective Equipment against SARS-CoV-2 and Multidrug-Resistant Bacteria. Image Credit: Kamil Macniak/ Shutterstock
The team observes that while the facial protection equipment is transparent and physically protects against microbial infections, it can be contaminated and a source of infection. Infected people may continue to transmit the infection despite wearing the protective equipment because it does not inactivate the microbial load transferred on it while breathing, sneezing, or coughing. Once infected, it constitutes an increasing source of biological waste - an environmental risk associated with the waste management of this protective equipment.
In the current study, the researchers fabricated the next generation of facial protective equipment - composed of an antimicrobial coating of benzalkonium chloride (BAK) on the polyethylene terephthalate (PET). This single-use transparent antimicrobial face shield inactivates enveloped viruses, such as severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) in less than one minute of contact and the methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus epidermidis (MRSE).
SARS-CoV-2 is demonstrated to be transmitted by contaminated material surfaces, in addition to aerosol transmission. Infectious microorganisms such as the influenza virus and S. pneumoniae are important global risks for respiratory infection deaths. Face shields are one of the protective equipment choices that form a physical barrier between the wearer and such biological agents, thus avoiding the agent's entry through the respiratory and mucosal tracts.
A preprint version of the study is available on the Preprints* server while the article undergoes peer review.
Preparation of the antimicrobial coating and testing
Facial protective equipment is commonly fabricated using PET, a commercial low-cost transparent and recyclable polyester. PET does not possess antimicrobial activity.
The researchers used a quaternary ammonium compound, such as benzalkonium chloride (BAK), to impart the antimicrobial activity to the face shield. BAK is reported to inactivate enveloped RNA viruses and gram-positive multidrug-resistant bacteria. The PET sheets were dip-coated with 70% ethyl alcohol with 0.1% w/w BAK for 1 min at 25 °C. This was followed by drying at 60 °C for 48 h and sterilizing under UV radiation for 1 hour.
The researchers demonstrated the antimicrobial properties of the BAK coating using atomic force microscopy and field emission scanning electron microscopy with elemental analysis and confirmed its opacity.
Antimicrobial activity against viruses and bacteria
During this ongoing COVID-19 pandemic, severe pneumonia, caused by bacteria such as Streptococcus pneumoniae, is associated with the SARS-CoV-2 infection. Such bacterial infections are increasingly resistant to antibiotics and raise the risk of mortality by co-infection.
The researchers studied the antibacterial activity of the fabricated disks against the phage Phi 6 (DSM 21518) and SARS-CoV-2, and the MRSA, COL, and MRSE, RP62A by the agar disk diffusion tests. They observed potent antiviral and antibacterial activity.
They also tested for the antimicrobial durability of the BAK coating when washed with water. Because BAK is highly water-soluble, the BAK coating is easily washed off. Therefore, the surface loses its antimicrobial activity, rendering the face shield a single-use face protective equipment.
Importantly, the proposed PET plastic can be recycled and reutilized - the BAK coating can be easily applied to the PET surface. Applying this ensures reduced waste generation caused by the increased use of such protective systems.
The mechanism of antimicrobial action
The positively charged nitrogen atoms in BAK damage the bacterial surface or disrupt the phospholipid bilayer membrane, the glycoproteinaceous envelope, and the spike glycoproteins of viruses such as phi6, SARS-CoV-2, and IFV. However, BAK is a Food and Drug Administration (FDA)-approved product used in disinfecting applications such as additives in soaps and hand sanitizers; thus, it is safe to use.
This work demonstrated a fabricated transparent face shield capable of providing extra protection by acting as a physic barrier with intrinsic antimicrobial activity against enveloped viruses such as SARS-CoV-2 and multidrug-resistant bacteria. It is a single-use antimicrobial face shield made by a low-cost procedure consisting of dip-coating polyethylene terephthalate with benzalkonium chloride.
Figure 7. Applications of the coating technology of transparent polyethylene terephthalate with an antimicrobial coating of benzalkonium chloride for the next generation of facial protective equipment: face shields, plastic masks, helmets, goggles, helmets and space separation screens
Notably, this antimicrobial material is recyclable, and it reduces the generation of infectious biological waste. It can be used for other protective equipment such as goggles, helmets, plastic masks, space separation counters, or vehicle screens to protect from ongoing viral infection and future variants. The researchers state that this low-cost technology would be very useful to combat the current COVID-19 pandemic and protect health care workers from multidrug-resistant infections in developed and underdeveloped countries.
Preprints publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.