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PERSPECTIVE
Year : 2020  |  Volume : 9  |  Issue : 5  |  Page : 62-67

Use of antiviral nanocoating in personal protective wear


Division of Nanoscience and Technology, Faculty of Life Sciences, JSS Academy of Higher Education and Research, Mysuru, Karnataka, India

Date of Submission02-May-2020
Date of Decision04-May-2020
Date of Acceptance12-May-2020
Date of Web Publication04-Jun-2020

Correspondence Address:
Dr. Asha Srinivasan
Division of Nanoscience and Technology, Faculty of Life Sciences, JSS Academy of Higher Education and Research, Mysuru - 570 015, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijhas.IJHAS_80_20

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  Abstract 


The emergence of the new coronavirus and its associated fatalities are growing at an alarming rate causing unprecedented losses worldwide. As the coronavirus disease 2019 pandemic accelerates in India, access to basic personal protective wear such as masks for health-care workers and for the general public is a key concern. Aerosol transmission of biological particles such as viruses is only one of several routes of exposure for contagion of which personal protection such as masks must be used by the general public. The protection level offered by N95 and surgical masks is defined by the percent of ambient particles penetrating across the protective mask. Recent interventions in nanotechnology have effectuated need-based virus resistance masks developed by impregnating nanomaterials or nanocoatings in the mask to combat the virus and augment protection levels. The aim of this review will be to highlight the coherent strategies of using versatile nanomaterials as an effective antiviral material coated onto masks and understanding the mechanism of “virus-nanoparticle” interaction. This viricidal effect is made possible by the use of functionalized nanoparticles through the addition of biomolecule covers or modified surfaces capable of interacting with active sites present on the membrane (capsid) allowing the virus to be deactivated.

Keywords: Contagion, cost-effective personal protective wear, coronavirus disease 2019, nanomaterials and nanocoatings, particle size, PM2.5


How to cite this article:
Chiome TJ, Srinivasan A. Use of antiviral nanocoating in personal protective wear. Int J Health Allied Sci 2020;9, Suppl S1:62-7

How to cite this URL:
Chiome TJ, Srinivasan A. Use of antiviral nanocoating in personal protective wear. Int J Health Allied Sci [serial online] 2020 [cited 2020 Jul 15];9, Suppl S1:62-7. Available from: http://www.ijhas.in/text.asp?2020/9/5/62/285971




  Introduction Top


With more than 2 million cases globally, coronavirus disease 2019 (COVID-19) will be one of the historical pandemics that the fragile humanity has ever experienced such that the unpreparedness even among the well-resourced countries, the current situation has caused immense losses in all facets (loss of lives, communities, and crashed economies) and severe shortages of essential commodities for health-care workers and for the general public at large. The transmission of coronavirus has been predominantly from person to person through droplets produced when one sneezes or coughs allowing the contagion droplets to enter the body through the nose or mouth. In addition to aerosol and fomite transmission, it has been discovered that even over a period of 3–4 h the virus will still be infectious while the period of viability is even extended to several days on some surfaces based on inoculum shed.

Under these pandemic circumstances, personal protective wear (PPW) such as overalls, masks, respirators, gloves, and other PPW/personal protective equipment (PPE) have become mandatory for health-care professionals and for the general public. Currently, there is a disruption in the supply of PPW globally as a result of increase in product demand, stockpiling, and abuse of the available PPW, thereby putting lives at risk. PPW (in health-care sector) is used to create a barrier between a health-care worker and an infectious agent in the form of a patient and reduce the risk of transmitting the infection to the general public. It is expected that the PPW should protect the individual from virus, bacteria, or particulate matter of all sizes.


  Particle Size Matters for Personal Protective Wear Top


The diameter of coronavirus strains varies from 60 to 140 nm[1] making it smaller in size than the PM2.5 cutoff yet greater than gasses and dust particles [Figure 1]. Cumulative long-term exposure to particulate matter classified as PM2.5 has caused a considerable number of deaths over the years. Microorganisms are known to exist in particulate matter as bioaerosols, but the interaction of viral contagion with particulate matter is comparatively unknown.
Figure 1: Size distribution of various compounds[3]

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In one study, the contagion of viruses suspended in PM2.5 was compared to viruses suspended in high-efficiency particulate air-filtered air by measuring the virus decay. It was discovered that the infection of airborne viruses is influenced by exposure to PM2.5 while different viruses show different effects.[2] Such findings provide guidance on the appropriate selection of PPW for preventing transmission of viruses including coronavirus to health workers or among the general public.


  Mask as Personal Protective Wear Top


There are two kinds of commercially available masks, 3-ply-surgical masks, and N95 respirators. The filters fitted onto N95 mask are capable of blocking particles as small as 0.3 μ and designed for a tight fit.[4] A study reported that N95 respirators do not provide adequate protection against aerosolized bacteriophage MS2 virus which is smaller than the 300 nm cutoff, thereby the efficiency of the mask falls below the claimed 95% efficiency and even lower when higher inhalation rates are present.[4] On the other hand, surgical masks are meant to block particle droplets of larger sizes while being looser fitting as compared to N95 respirators. As the surrounding air already contains particulate matter, surgical masks allow for a significant number of airborne pathogens to pass through the filters, thereby offering very little protection against airborne components of 10–80 nm, of which the coronavirus falls within this range. The surgical masks are designed in such a way that it protects the surrounding environment from the person wearing it whereas the N95 respirators protect the wearer from the environment.[4]

Due to inflated prices of N95 and surgical masks, household cotton material is also used due to its comfort and availability. With a study done to measure the efficiency of different materials which are used to make makeshift masks based on their ability to filter 1-μ particles, most construction workers use dish towels which were 83% efficient and the rest of the population is using cotton facemasks which showed 69%–74% efficiency.[5] Having such a low efficiency for such large particles, these makeshift masks are fighting a losing battle against the coronavirus which is ×10 smaller [Figure 2]. A strategy to overcome these inadequacies and nanomaterials incorporated in the form of nanocoatings provides several durable functional advantages.
Figure 2: Household material effectiveness against 1-μ particles[5]

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  Nanomaterials as Antivirals Top


The efficacy of conventional antiviral therapies is gradually fading due to accelerated adaptations by peripheral viral proteins which have led to nanotechnology achievements for the engineering of versatile nanomaterials. Taking into consideration the severity of the virus infection, it is imperative to understand the virus-nanoparticle interaction mechanism as a promising alternative. From a physics perspective, viruses are nanoparticles of specific shapes having features intrinsic to those of near field.[6],[7] When the “virus-nanoparticle” complex is in close proximity, local field enhancement takes place that can suppress active centers on the viral capsids and debilitate the chemical bonds within the capsid. By modifying the receptors present on the viral capsid, this will render the virus harmless as it would have lost its ability to infect nor penetrate the host cells [Figure 3].[8] These mechanisms on binding energies and local field interactions have presented several nanomaterials with unique properties creating a progressive novel area of research in nanoscience.
Figure 3: Molecular dynamics. (a) View of a small sulfonated MUS: OT-NP (2.4 nm core) binding to HPV capsid L1 protein pentamer. Red and yellow spheres show negatively charged terminal sulfonate groups of the MUS-NP. Positively charged HSPG-binding residues of L1 shown in blue. (b) Illustration of multisite binding of MUS-type nanoparticles to HSPG-binding residues changing arrangement of L1 capsid proteins. Scale bars are 1 nm. MUS-OT – 1-octanethiol (OT) and 11-mercapto-1-undecane sulfonic acid (MUS); HVP – Human papillomavirus; HSPG - Heparan sulfate proteoglycans[9]

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This review attempts to harmonize the various PPW options based on the use of nanomaterial coatings taking into account commercially available or products still in the pipeline based on scientific evidence. Nanomaterial-virus interactions have been an emerging field that has allowed innovators to look at curbing COVID-19 from a different angle allowing us to deal with the virus using particles having the same size as the virus itself. This creates a new perspective to problem-solving allowing for the creation of affordable and more efficient medical solutions to mitigate the growing virus transmission clinical and public health challenges.


  Nanocoatings to Curb Coronavirus Disease 2019 Spread Top


Nanocoatings

Nanocoatings have been effective in most products in the markets as they are 99.99% effective against various forms of viruses, molds, and bacteria.[15] Due to their functional efficiency, global partnerships are already being developed to work together in the manufacturing of PPW.[11] Nanocoatings allow for a dual-purpose single coating capable of providing both antiviral and antibacterial activity while still being environmentally friendly and biocompatible.

The use of nanomaterials such as silver, carbon nanotubes, and titanium dioxide nanoparticles in coatings allows for the reduction of surface contamination as the coating gives the surface self-cleaning, hydrophobic, and odor-masking properties such that there will be reduced cleaning efforts required. With the coating being a few nanometers thick, the nanocoating allows creation and material functionality acting as an interface between the substrate and the surrounding environment. Such coatings are so thin that they are transparent to the naked eye yet applicable to various surfaces and materials. With such unique applications, TechNavio reported a Compound annual growth rate (CARGR) growth of 25% for the 2016–2020 period [Figure 4],[10] and due to the COVID-19 pandemic, this projected growth is expected to rise over the projected horizon.[11]
Figure 4: Global nanocoating market[10]

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Several methodologies have been proposed to prepare antimicrobial coatings that require a multistep process with certain surface chemistries. Photosensitive materials such as porphyrins and metalloporphyrins at certain wavelengths are able to produce reactive intermediates that produce short lifespan reactive oxygen species (40 ns) which have Microbicidal effect by binding to the membrane of bacteria.[12] These materials were called as light-activated antimicrobial (LAAM). In 2006, Michielsen et al. group nanocoated the LAAMs (5–10 nm thick) the materials presented an enhanced antiviral effect. The study reported that the antiviral nanocoating had 99.9% viricidal effect on influenza and vaccinia virus upon exposure to light. The performance trials of the LAAM nanocoating were tested in specific hospitals in North Carolina. This study on LAAM was filed for a patent, and since then, LAAM science has raised over US$ 400,000 in seed financing investors.

A Japan-based company, NanscNano Technology Ltd., has developed a specialized technology termed Medical Nanocoat. Medi Nanocoat [Figure 5] is a patented liquid spray that offers sustainable defense against bacteria. Through this technology, the scientists have been able to coat medical equipment [Figure 5] along with bedcovers, medical clothing, glass partitions, and hospital curtains with this nanocoating introducing antibacterial and antiviral properties to the surfaces.[13]
Figure 5: Medi Nanocoat liquid sprayed and nanocoated medical equipment (adapted from Multifunctional Nanocoating Technologies, United Nations Industrial Developmental Organization, Tokyo)

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Given the current COVID-19 situation, the probability of the airborne transmission of the virus depends in part on the amount of aerosolized contagion to which people are exposed to. In reality, a cough contains various particles ranging from 8 to 114 μm having small, medium, and large particles. The grain size in nanocoatings ranges from 8 to 100 nm and several micrometers in thickness which can contain the viruses of various sizes within the layers of the coatings.

Affordable antimicrobial spray-based coating for personal protective equipment

In India, the Indian Institute of Technology, Guwahati, developed a nanocoating spray containing copper and silver nanoparticles [Figure 6]. The coating limits viral accumulation and penetration through PPE material as it kills microbes as soon as they come into contact with the coating, in turn, limiting viral transfer. Not only limited to antiviral function, the coating also allows PPE materials to be reused, thereby addressing the problem of shortage of PPW being faced by many nations. This product is advantageous as it is affordable and can be produced using the basic infrastructure already available, and without any special skill required, the coating can be applied by spraying or dip coating the fabric materials.[14]
Figure 6: Antimicrobial nanocoating spray[14]

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Nanofilters

As the virus spreads mainly through droplets, the public is advised to always wear facemasks so that they will not spread the virus while talking, coughing or sneezing as the filters on the mask prevent the crossing of the droplets.

Due to the high demand of protective wear most countries have imposed laws that they manufacturers can not exports such materials as a way to make sure that its own citizens have enough supplies first[16]. Regardless of such measures, the supply is still not meeting the growing demand leaving people with no other option but to make makeshift masks and overuse the limited number of disposable masks they have.[17] Commercially available surgical masks being used by the population are reported to be 89% effective at stopping the virus, but due to the unavailability of such masks, the population ends up using cotton masks and makeshift masks made from cotton which only offers 51% protection.[5],[18] In order to increase the efficiency of such poor performing materials, researchers are using nanotechnology as a way to bridge the gap and improve the filtering efficiency.

When facemasks are made wet, they tend to lose their filtering capability as there is a disruption in the material's electrostatic function making them unusable anymore. The Korea Advanced Institute of Science and Technology developed a washable nanofilter which would allow it to be reused and inserted on the inside of surgical masks. The nanofilter having aligned nanofibers was developed using block electrospinning which produced fibers of 100–500 nm. After being repeatedly washed and sterilized with ethanol, the nanofilter still retained its efficiency even after repeating the process up to 20 times and it maintains 94% efficiency. To examine the stability of the material, the nanofilter was soaked in ethanol for 3 h, but its composition still remained unaltered. To test the durability of the filter, it was put through the bending test, and even after 4000 cycles, it was 80% efficient. The startup has a setup capable of producing up to 1500 nanofiber filters in a day.[19]

The Hong Kong Polytechnic University has developed an electrostatic charged nanofiber filter capable of filtering nanoaerosols of 100 nm. The nanofilter was made using polyvinylidene fluoride (PVDF) which created electrostatic charged material to help trap aerosol as it increased the electrical interaction. By making the PVDF charged, it increased the quality factor 2.7 times. To minimize the interactions between the charged layers, a layer of separator was placed between the layers so as to reduce interference between them. This particular invention makes it the most ideal tool against COVID-19 as the virus is negatively charged and the nanofiber is positively charged, thereby increasing filtration making it ×10 higher than that of micron-sized filters yet still having high breathability and longer shelf life of up to 90 days.[20]

Antiviral clothing

Protective clothing worn by health-care workers is efficient at preventing the virus from reaching their bodies, thereby allowing the microbes to accumulate of the PPE. Thereby, the use of nanotechnology can help guarantee the death of the microbes when they come into contact with the material. Such an effect is made possible by treating the fabrics with nanomaterial using different dedicated methods.

HeiQ, a Swiss-based company, developed HeiQ Viroblock NPJ03, an antiviral textile treatment which has been tested on facemasks and has proved to have the ability to reduce antiviral log of the masks from 2.9 to 4.48 between the untreated and treated masks. This treatment allows the textile to not be a carrier of viruses, thereby reducing the risk of contamination as well as transmission. HeiQ treatment makes the use of vesicle technology which targets viruses with a lipid envelope allowing for them to be rapidly deactivated while its silver technology inhibits replication of the microbes. The technology allows for long-lasting protection even after multiple washes and can be used on multiple textiles which include curtains, masks, air filters, or surgical gowns. The antiviral and antibacterial protection treatment resulted in more than 99.99% reduction of coronavirus (229E), H1N1, H5N1, and respiratory syncytial virus.[21]

In another study, an antiviral gown was developed which had three layers of polypropylene, polytetrafluoroethylene, and polyester as outer, middle, and inner layers, respectively, with a 70 g/m[2] basic weight and then treated titanium dioxide nanodispersion with 9 nm particles. Penetration test proved that the treated material was inimical to hepatitis B and hepatitis C, HIV, and Phi-X174 bacteriophage. The material had micropores which allowed for breathability and allowed the material to have good moisture vapor permeability which would allow for comfort even when worn for prolonged periods.[22]

Sonovia, an Israeli startup, makes use of ultrasonic fabric finishing technology which was developed by chemistry professors from Bar-Ilan University. The technology mechanically incorporates zinc and copper oxide nanoparticles into materials of PPW [

[Figure 7]. Preliminary data have shown that the treatment made the materials antibacterial against six bacteria which include Escherichia coli and Staphylococcus with the treatment remaining effective even after 100 washes at 75°C and 65 washes at 92°C. Being antiviral in nature, it offers protection against multiple strains of influenza, including present COVID-19 strain.[23]
Figure 7: Sonovia fabric treatment process using antibacterial nanoparticles[23]

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Argaman in Jerusalem is also working toward commercialization of their Bio-Block mask and CottonX cloth made from cotton embedded with copper oxide nanoparticles and nanofiber to block pathogen path. The nanofibers have nanopores so small that they do not allow the entry of droplets nor virus, thereby blocking entry and killing the pathogens at the same time. The mask can be washed 100 times at home while only surviving 50 industrial washes. A test conducted by the Centers for Disease Control and Prevention on Argaman's bedding and gowns concluded that the materials reduced the transmittance of multidrug-resistant pathogens by 50%. Just like Sonovia textile, CottonX fabric also proved to be effective against COVID-19.[23]


  Conclusion Top


Viruses are nanoscale organic particles, and selective nanomaterials with tunable surface chemistry can modulate the viral activity. This review is an attempt to correlate the size of the virus and nanoparticles embedded in the nanocoatings, nanofilters, or antiviral clothing and proposed a generalized mechanism of antiviral action of nanomaterials on the virus. The interaction among virus-nanoparticle complex creates a pathway for allowing the suppression of an infection's virulence due to local field effect while relying on size, morphology, and nanoparticle concentration more than the nanoparticle type. Different types of viruses can lead to different types of local field effect when located close to nanomaterials leading to a strong suppression of viral contagion ability. This physical mechanism of antiviral activity is considered as a new field of study in nanoscience. By understanding local field mechanisms, cost-effective PPW/E with efficient protection can be manufactured. Exploring nanotechnology solutions will offer efficient and durable products which will remain relevant even after the pandemic and still find a purpose in today's polluted environment.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]



 

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