Enhanced Antimicrobial Activity on Non-Conducting and Conducting Air Filters by Using Air Ions and Grapefruit Seed Extract

Abstract

The application of grapefruit seed extract (GSE) and air ions to filters was investigated with the goal of collecting indoor bioaerosols. GSE exhibits antimicrobial activity because it contains flavonoids such as naringin. Air ions are usually generated by electric ionizers and can inactivate bacteria, viruses, and fungi. In this study, GSE particles were coated onto three different filters: polypropylene (PP), activated carbon fiber (ACF), and metal foam (MF). Ions were supplied to the filter surface using an ionizer. The rate of surface inactivation of Staphylococcus aureus was measured. When only GSE was applied to the filters, the inactivation rate was about 60%; when air ions were applied, the rate was about 70-80%. When both GSE and ions were applied simultaneously, the inactivation rate increased to 80-90%. The physical collection efficiencies of the as-purchased filters were in the following order: PP > ACF > MF. However, when ions were supplied to the filters, the collection efficiencies increased to over 98% for each filter. The inactivation rate of the ACF filter was the highest (92.5%). Therefore, we conclude that the ACF filter is the most efficient of these three filters for inactivating S. aureus.

Face Masks in the New COVID-19 Normal: Materials, Testing, and Perspectives

“…The produced MOF filters demonstrated excellent performance for PM removal under a wide range of working temperatures from 80 to 300°C. The PM removal efficiency of the ZIF-8@plastic mesh (Figures 11(c Meanwhile, the accumulation of microorganisms in the filter also blocks the filter, leading to reduced ventilation volume and deterioration of the filter [160][161][162]. Thus, it is highly desirable to develop air filters with antimicrobial properties, especially when the filters are used for respiratory protection, such as masks, and for indoor air purification.…”

“…Though air filters discussed above show excellent capture efficiency for particular matters (PM), microorganisms (or bioaerosols), such as bacteria, viruses, and fungi in the air, adhere to the filter surface, remain viable, and may reproduce within the filter media, which pose a risk of second airborne contamination. Meanwhile, the accumulation of microorganisms in the filter also blocks the filter, leading to reduced ventilation volume and deterioration of the filter [ 160 – 162 ]. Thus, it is highly desirable to develop air filters with antimicrobial properties, especially when the filters are used for respiratory protection, such as masks, and for indoor air purification.…”

“…Antimicrobial extracts of natural products have been widely studied as antimicrobial agents for air filters owing to their high antimicrobial activity, low toxicity, low-cost, and gentleness to the environment [ 163 – 165 ]. The microbial toxicity of natural product extracts is generally accredited to the flavonoids they may contain, which kill microbes via the damage of cell membrane function and inhibition of DNA gyrase [ 160 , 162 ]. Herbal extracts, such as tea tree oils [ 166 ], extract of olive [ 161 ], extract of Euscaphis japonica [ 164 ], grapefruit seed extract [ 165 ], mangosteen extracts [ 167 ], and especially Sophora flavescens [ 168 – 170 ], have been sprayed on the surfaces of fibrous polymeric filter for antimicrobial properties, and the herbal extract-coated filter demonstrated good antimicrobial activity.…”

Masks for COVID‐19

“…[262] In general, the antimicrobial performance of herbal extracts is commonly attributed to the flavonoids that they may contain, which can kill microorganisms by disrupting cell membrane function and inhibiting deoxyribonucleic acid (DNA) cyclase. [263,264] Besides licorice extracts, it was also found that some herbal plants with antimicrobial properties, such as sage, garlic, oregano, fennel, etc., can reduce some symptoms of infectious individuals and may prevent the transmission of COVID-19. [265][266][267][268][269] In addition, Sim et al developed an Activated Carbon Fiber (ACF) filter incorporated with Sophora Flavescens, and they reported that the ACF filter showed an antibacterial efficiency >90%.…”

Advances in Facemasks during the COVID-19 Pandemic Era

“…Hence, they can become localized in the filter and their population can grow, which decreases filter quality and impacts air purification. Further, viable organisms present in the filter cause secondary infection after disposal, which is a major cause of the spread of disease. − Various antimicrobial agents, such as graphene, MOFs, metal oxide, and NPs, can be incorporated in the filter to remove microbial load and efficiently filter air …”