Antimicrobial, or hygienic, coatings have been around for many years. Rather than using preservatives only for in-can preservation, these functional coatings provide active protection against microorganisms in the applied film state. They are used on heating and air conditioning systems, food processing equipment and facilities, medical implants, personal care and home appliances, and ship hulls. They are extremely important today in light of the COVID-19 pandemic, because antimicrobial coatings are also used on the walls, floors, and railings of hospitals and schools and residential, industrial, and institutional countertops and are sprayed onto masks, gloves, and other textiles. Some rely on silver or natural minerals, others on fungicides and biocides, and yet others on enzyme-based technologies. Both liquid and powder options are available today. Market research firm Global Market Insights estimates the value of the global antimicrobial coatings market is expanding at a compound annual growth rate of 10.4%, from $3.2 billion in 2019 to $6.3 billion by 2026. Health-care applications are predicted to account for greater than $1.9 billion of antimicrobial coating sales by the end of 2026.
Viruses such as SARS-CoV-2, the virus that causes COVID-19, generally range in size from 100–300 nm and are much smaller than bacteria. They comprise nucleic materials (DNA or RNA) surrounded by proteins that protect them from the environment and enable them to bind to specific sites on host cells. Enveloped viruses (including SARS-CoV-2) also contain an outer layer composed of lipids, polysaccharides, and proteins that allow the virus to more easily fuse with and enter host cells. To survive and reproduce, viruses must eventually infect a living host. Coronaviruses such as SARS-CoV-2, however, have been shown to survive on metal, glass, wood, fabric, and plastic surfaces for several hours to days. Therefore, destroying or damaging viruses while they exist on surfaces can prevent infection and the spread of disease. Many different types of nanoparticles have been shown to be effective at inactivating viruses, including coronaviruses such as SARS-CoV-2. For example, nanoscale zinc oxide, cuprous oxide, silver, copper iodide, gold on silica, and quaternary ammonium cations (quats) have all shown promise.1
Coronaviruses such as SARS-CoV-2, however, have been shown to survive on metal, glass, wood, fabric, and plastic surfaces for several hours to days. Therefore, destroying or damaging viruses while they exist on surfaces can prevent infection and the spread of disease.
Due to the COVID-19 pandemic, much research is being focused on the development of antiviral coatings. Antiviral coatings are a subset of antimicrobial coatings. Some antimicrobial coatings can kill viruses as well as bacteria and other microorganisms (i.e., mold and fungi), while others are not designed to destroy viruses. One example of a coating approved by the U.S. Environmental Protection Agency that targets viruses is Caliwel™ BNA Coating from Allistagen Corporation. This coating is based on calcium hydroxide and has been proven effective against more than 20 life-threatening bacteria, viruses, and fungi, according to the company.2
Nova Surface-Care Centre Pvt. Ltd. believes its NANOVA HYGIENE+™ product, a low-surface-
energy coating (repels both oil and water) containing a combination of nano-actives (quats, positively charged silver nanoparticles) that can be applied to fabrics, plastics, metals, and concretes has the potential to inactivate SARS-CoV-2.1 The coating has been shown to be effective against bacteria, fungi, and algae. An initial test against the small nonenveloped RNA virus MS2 Bacteriophage (Poliovirus) showed 99.9% antiviral efficacy in just two hours according to global standard AATCC 100-2012. A test is currently underway to establish the coating’s performance against SARS-CoV-2.
Researchers at the Hong Kong University of Science and Technology report the development of an antiviral that, when sprayed onto frequently touched surfaces, could provide 90 days of “significant” protection against bacteria and viruses, including SARS-CoV-2.3 The coating is based on what the scientists refer to as a multilevel antimicrobial polymer (MAP-1) and contains millions of nano-capsules formed with heat-sensitive polymers that contain disinfectants. The polymers release the disinfectants when warmed by human contact. Clinical tests were conducted at a Hong Kong hospital and a home for the elderly, and now the coating is commercially available through the university’s industrial partner Chiaphua Industries Ltd. A local charity stepped in to help, spraying the non-toxic coating around the homes of more than a thousand low-income families in Hong Kong.
Nippon Paint and Corning, Inc. began work to develop an antiviral coating in June 2019.4 The COVID-19 pandemic accelerated work on the project. The resulting coating, Nippon Paint’s Antivirus Kids Paint, contains Corning’s Corning Guardiant™ Antimicrobial Particles and was tested by Microchem Laboratory, an accredited, independent laboratory in the United States, in January. The paint was shown to inactivate > 99.9% of the Feline Calicivirus (an EPA-approved representative for human norovirus) and to kill > 99.99% of harmful bacteria including Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa under the latest test protocols that mimic contamination in everyday indoor environments. Nippon Paint kids paint by itself is environmentally friendly and TÜV and GREENGUARD certified. In March, Nippon Paint China and Corning Inc. donated 5 million RMB worth of the antiviral coating, which was specially produced for frontline hospital use and is not yet available on the market, to four Hubei coronavirus-designated hospitals.
Researchers at the Hong Kong University of Science and Technology report the development of an antiviral that, when sprayed onto frequently touched surfaces, could provide 90 days of “significant” protection against bacteria and viruses, including SARS-CoV-2.3 The coating is based on what the scientists refer to as a multilevel antimicrobial polymer (MAP-1) and contains millions of nano-capsules formed with heat-sensitive polymers that contain disinfectants.
In one other example, materials company Nobio, Ltd. received a $205,000 grant in April 2020 from the Israel Innovation Authority to support the development and manufacture of a long-acting surface coating containing its patented antimicrobial technology.5 Nobio received FDA clearance in 2019 for its Infinix antimicrobial dental restorations (fillings) and expects to launch them in the second half of 2020. With the new grant money, the company will apply similar nanoparticle-based antimicrobial technology to develop antiviral facemasks and long-acting surface coatings. Nobio is currently working with contract manufacturers to enable scale-up and production of the face masks and coatings.
References
- Swapan Kumar Ghosh, “Anti-Viral Surface Coating to Prevent Spread of Novel Coronavirus (COVID-19) Through Touch,” Coatings World, April 15, 2020. https://www.coatingsworld.com/content-microsite/cw_covid-19/2020-04-15/anti-viral-surface-coating-to-prevent-spread-of-novel-coronavirus-covid-19-through-touch.
- Allistagen, “EPA-Approved Antimicrobial Surface Coating Represents Breakthrough in the Control and Spread Of Infectious Diseases,” Press Release, March 19, 2020. https://www.prnewswire.com/news-releases/
epa-approved-antimicrobial-surface-coating-represents-breakthrough-
in-the-control-and-spread-of-infectious-diseases-301027074.html. - Reuters, “HK scientists say new antiviral coating can protect surfaces for 90 days,” Health News, April 27, 2020. https://www.reuters.com/article/us-health-coronavirus-hongkong-coating/hk-scientists-say-new-antiviral-coating-can-protect-surfaces-for-90-days-idUSKCN2290S5.
- Nippon Paint, “Nippon Paint and Corning Incorporated donated lab-tested antivirus coatings to hospitals in Hubei,” Press Release, March 16, 2020. https://prnmedia.prnewswire.com/news-releases/
nippon-paint-and-corning-incorporated-donated-lab-tested-antivirus-
coatings-to-hospitals-in-hubei-301024778.html. - Nobio Ltd., “Nobio Secures Grant from the Israel Innovation Authority for Protective Measures Against Covid-19,” Press Release, April 9, 2020. https://prnmedia.prnewswire.com/news-releases/nobio-secures-
grant-from-the-israel-innovation-authority-for-protective-measures-
against-covid-19-301038123.html.
CoatingsTech | Vol. 17, No. 7 | July 2020