A critical evaluation of current protocols for self-sterilizing surfaces designed to reduce viral nosocomial infections

Nano-antivirals: A comprehensive review

Nanoparticles can be used as inhibitory agents against various microorganisms, including bacteria, algae, archaea, fungi, and a huge class of viruses. The mechanism of action includes inhibiting the function of the cell membrane/stopping the synthesis of the cell membrane, disturbing the transduction of energy, producing toxic reactive oxygen species (ROS), and inhibiting or reducing RNA and DNA production. Various nanomaterials, including different metallic, silicon, and carbon-based nanomaterials and nanoarchitectures, have been successfully used against different viruses. Recent research strongly agrees that these nanoarchitecture-based virucidal materials (nano-antivirals) have shown activity in the solid state. Therefore, they are very useful in the development of several products, such as fabric and high-touch surfaces. This review thoroughly and critically identifies recently developed nano-antivirals and their products, nano-antiviral deposition methods on various substrates, and possible mechanisms of action. By considering the commercial viability of nano-antivirals, recommendations are made to develop scalable and sustainable nano-antiviral products with contact-killing properties.

Permanent, Antimicrobial Coating to Rapidly Kill and Prevent Transmission of Bacteria, Fungi, Influenza, and SARS-CoV-2

Microbial adhesion and contamination on shared surfaces can lead to life-threatening infections with serious impacts on public health, economy, and clinical practices. The traditional use of chemical disinfectants for sanitization of surfaces, however, comes with its share of health risks, such as hazardous effects on the eyes, skin, and respiratory tract, carcinogenicity, as well as environmental toxicity. To address this, we have developed a nonleaching quaternary small molecule (QSM)-based sprayable coating which can be fabricated on a wide range of surfaces such as nylon, polyethylene, surgical mask, paper, acrylate, and rubber in a one-step, photocuring technique. This contact-active coating killed pathogenic bacteria and fungi including drug-resistant strains of Staphylococcus aureus and Candida albicans within 15-30 min of contact. QSM coatings withstood multiple washes, highlighting their durability. Interestingly, the coated surfaces exhibited rapid killing of pathogens, leading to the prevention of their transmission upon contact. The coating showed membrane disruption of bacterial cells in fluorescence and electron microscopic investigations. Along with bacteria and fungi, QSM-coated surfaces also showed the complete killing of high loads of influenza (H1N1) and SARS-CoV-2 viruses within 30 min of exposure. To our knowledge, this is the first report of a coating for multipurpose materials applied in high-touch public places, hospital equipment, and clinical consumables, rapidly killing drug-resistant bacteria, fungi, influenza virus, and SARS-CoV-2.

Antimicrobial polymeric composites for high-touch surfaces in healthcare applications

Antimicrobial polymer composites have long been utilized in the healthcare field as part of the first line of defense. These composites are desirable in that they pose a minimal risk of developing contagions with antibiotic resistance. For this reason, the field of antimicrobial composites has seen steady growth over recent years and is becoming increasingly important during the current COVID-19 pandemic. In this article, we first review the need of the antimicrobial polymers in high tough surfaces, the antimicrobial mechanism, and then the recent advances in the development of antimicrobial polymer composite including the utilization of intrinsic antimicrobial polymers, the addition of antimicrobial additives, and new exploration of surface patterning. While there are many established and developing methods of imbuing a material with antimicrobial activity, there currently is no standard quantification method for these properties leading to difficulty comparing the efficacy of these materials within the literature. A discussion of the common antimicrobial characterization methods is provided along with highlights on the need of a standardized quantification of antiviral and antibacterial properties in testing to allow ease of comparison between generated libraries and to facilitate proper screening. We also discuss and comment on the current trends of the development of antimicrobial polymer composites with long-lasting and specific antimicrobial activities, nontoxic properties, and environmental friendliness against a broad-spectrum of microbes.

Ag-enriched TiO2 nanocoating apposite for self-sanitizing/ self-sterilizing/ self-disinfecting of glass surfaces

The excellent strategy to mitigate the spread of the COVID-19 pandemic is to inhibit the transmission of the SARS-CoV-2. Since fomites are one of the vital routes of coronaviral transmission, disinfecting of fomites play a pivotal role in curbing its survival on the contaminated surfaces. Available commercial disinfectants cannot keep the contaminated surfaces sanitized all the time. Self-disinfecting ability of Ag-enriched TiO₂ nanocoating due to its superb photocatalytic efficiency can effectively reduce infections caused by spread of pathogens at public places. Anatase Ag-TiO₂ nanocoatings synthesized by sol-gel process at 0.5, 1.5, and 2.5% enriching concentrations were casted on glass substrates by spin-coating technique and subsequently annealed at 650 °C. The morphological shape, crystallographic structure, light absorbance, photo-luminosity, vibrational modes, and functional groups of Ag-TiO₂ nanocoating on glass surface were studied by FE-SEM, GIXRD, UV-Visible, Photoluminescence, Raman, and FTIR spectroscopy. The developed anatase Ag-TiO₂ nanocoatings manifested to improve photocatalytic disinfecting performance due to the achieved small crystallite size of 10.5-19.2 nm, diminished band gap energy of 2.56-2.60 eV, elevated surface area of 0.802-1.470 ×10⁵ cm²/g, and enhanced light absorbance. Among the enriched specimens, 0.5% Ag-TiO₂ nanocoatings predicted an overall exalted functionality compared to pristine one.

Design strategies for antiviral coatings and surfaces: A review☆

The routine disinfection and sanitization of surfaces, objects, and textiles has become a time-consuming but necessary task for managing the COVID-19 pandemic. Nonetheless, the excessive use of sanitizers and disinfectants promotes the development of antibiotic-resistant microbes. Moreover, that improper disinfection could lead to more virus transfer, which leads to more viral mutations. Recently developed antiviral surface coatings can reduce the reliance on traditional disinfectants. These surfaces remain actively antimicrobial between periods of active cleaning of the surfaces, allowing a much more limited and optimized use of disinfectants. The novel nature of these surfaces has led, however, to many inconsistencies within the rapidly growing literature. Here we provide tools to guide the design and development of antimicrobial and antiviral surfaces and coatings. We describe how engineers can best choose testing options and propose new avenues for antiviral testing. After defining testing protocols, we summarize potential inorganic and organic materials able to serve as antiviral surfaces and present their antiviral mechanisms. We discuss the main limitations to their application, including issues related to toxicity, antimicrobial resistance, and environmental concerns. We propose solutions to counter these limitations and highlight how the context of specific use of an antiviral surface must guide material selection. Finally, we discuss how the use of coatings that combine multiple antimicrobial mechanisms can avoid the development of antibiotic resistance and improve the antiviral properties of these surfaces.

Network polymers incorporating lipid-bilayer disrupting polymers: towards antiviral functionality

Polymer based solid-state materials capable of disrupting lipid-bilayers are developed. The materials are mechanically robust and capable of outperforming a 10% small-molecule surfactant and modify filter materials.

Effectiveness of antiviral metal and metal oxide thin-film coatings against human coronavirus 229E

Virucidal thin-film coatings have the potential to inactivate pathogens on surfaces, preventing or slowing their spread. Six potential nanoscale antiviral coatings, Cu, Cu2O, Ag, ZnO, zinc tin oxide (ZTO), and TiO2, are deposited on glass, and their ability to inactivate the HCoV-229E human coronavirus is assessed using two methods. In one method, droplets containing HCoV-229E are deposited on thin-film coatings and then collected after various stages of desiccation. In the second method, the thin-film coatings are soaked in the virus supernatant for 24 h. The Cu and Cu2O coatings demonstrate clear virucidal behavior, and it is shown that controlled delamination and dissolution of the coating can enhance the virucidal effect. Cu is found to produce a faster and stronger virucidal effect than Cu2O in the droplet tests (3 log reduction in the viral titer after 1 h of exposure), which is attributed, in part, to the differences in film adhesion that result in delamination of the Cu film from the glass and accelerated dissolution in the droplet. Despite Ag, ZnO, and TiO2 being frequently cited antimicrobial materials, exposure to the Ag, ZnO, ZTO, and TiO2 coatings results in no discernible change to the infectivity of the coronavirus under the conditions tested. Thin-film Cu coatings are also applied to the polypropylene fabrics of N95 respirators, and droplet tests are performed. The Cu fabric coating reduces the infectivity of the virus; it results in a 1 order-of-magnitude reduction in the viral titer within 15 min with a 2 order-of-magnitude reduction after 1 h.

Virus matrix interference on assessment of virucidal activity of high-touch surfaces designed to prevent hospital-acquired infections

Objectives/purpose

High-touch surfaces are a critical reservoir in the spread of nosocomial infections. Although disinfection and infection control protocols are well developed, they lack the ability to passively reduce the pathogenic load of high-touch surfaces. Copper and its alloys have been suggested as a surface that exhibit continuous biocidal effects. Antimicrobial studies on these surfaces are prevalent, while virucidal studies are not as well explored. The goal of this study was to first determine the virucidal activity of a copper–nickel–zinc alloy and to then examine the effect of soiling and virus preparation on virucidal activity.

Methods

A baculovirus vector was used as an easily quantifiable model of an infectious enveloped animal cell virus. Droplets containing virus were deposited on surfaces and allowed to stay wet using humidity control or were dried onto the surface. Virus was then recovered from the surface and assayed for infectivity. To examine how the composition of the droplet affected the survival of the virus, 3 different soiling conditions were tested. The first two were recommended by the United States Environmental Protection Agency and the third consisted of cell debris resulting from virus amplification.

Results

A copper–nickel–zinc alloy was shown to have strong virucidal effects for an enveloped virus. Copper, nickel, and zinc ions were all shown to leach from the alloy surface and are the likely cause of virucidal activity by this surface. Virucidal activity was achieved under moderate soiling but lost under high soiling generated by routine virus amplification procedures. The surface was able to repeatably inactivate dried virus droplets under moderate soiling conditions, but unable to do so for virus droplets kept wet using high humidity.

Conclusion

Ion leaching was associated with virucidal activity in both wet and dried virus conditions. Soiling protected the virus by quenching metal ions, and not by inhibiting leaching. The composition of the solution containing virus plays a critical role in evaluating the virucidal activity of surfaces and surface coatings.

Fomite Transmission, Physicochemical Origin of Virus-Surface Interactions, and Disinfection Strategies for Enveloped Viruses with Applications to SARS-CoV-2

Inanimate objects or surfaces contaminated with infectious agents, referred to as fomites, play an important role in the spread of viruses, including SARS-CoV-2, the virus responsible for the COVID-19 pandemic. The long persistence of viruses (hours to days) on surfaces calls for an urgent need for effective surface disinfection strategies to intercept virus transmission and the spread of diseases. Elucidating the physicochemical processes and surface science underlying the adsorption and transfer of virus between surfaces, as well as their inactivation, is important for understanding how diseases are transmitted and for developing effective intervention strategies. This review summarizes the current knowledge and underlying physicochemical processes of virus transmission, in particular via fomites, and common disinfection approaches. Gaps in knowledge and the areas in need of further research are also identified. The review focuses on SARS-CoV-2, but discussion of related viruses is included to provide a more comprehensive review given that much remains unknown about SARS-CoV-2. Our aim is that this review will provide a broad survey of the issues involved in fomite transmission and intervention to a wide range of readers to better enable them to take on the open research challenges.

Fight against COVID-19: The case of antiviral surfaces

The COVID-19 pandemic is the largest global public health outbreak in the 21st century so far. Based on World Health Organization reports, the main source of SARS-CoV-2 infection is transmission of droplets released when an infected person coughs, sneezes, or exhales. Viral particles can remain in the air and on the surfaces for a long time. These droplets are too heavy to float in air and rapidly fall down onto the surfaces. To minimize the risk of the infection, entire surrounding environment should be disinfected or neutralized regularly. Development of the antiviral coating for the surface of objects that are frequently used by the public could be a practical route to prevent the spread of the viral particles and inactivation of the transmission of the viruses. In this short review, the design of the antiviral coating to combat the spread of different viruses has been discussed and the technological attempts for minimizing the coronavirus outbreak have been highlighted.

Gold hard anodized (GHA) materials with antimicrobial surface properties: mechanical, tribological, and microbiological characterization

Infections acquired in public spaces (i.e., transports, restaurants, and bars, hospitals) present a serious burden for the entire health systems. In this respect, appropriate preventative and control measures in order to eliminate or reduce the negative effects of surface-transmitted infections appear highly desirable. Alongside recommendations for treatment and hygiene, antimicrobial material surfaces can offer indeed an important contribution to the prevention of infections. The aim of the current paper is therefore to describe the preparation and characterization of a new material obtained by an innovative anodic oxidation, defined as golden hard anodizing GHA. The anodic oxide surface thanks to the nanoporous structure acts as reservoir of silver ions (Ag⁺) which in turn confer antimicrobial properties to the material surface. Specifically, the manuscript presents a thorough preparation and characterization of a new material obtained by an innovative anodic oxidation treatment applied on commercially available aluminum alloys including the microscopic analysis and the description of the antimicrobial performances against a number of microorganisms, including among the others, Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. More specifically, the current article describes some of the properties of GHA materials. The tribological properties of GHA were evaluated through experimental tests performed with a pin-on-disk tribometer. The morphology of the wear surfaces was studied by means of a scanning electron microscope (SEM) analysis and profilometry investigations. Furthermore, in order to evaluate the possible anticorrosive properties of GHA, tests in neutral salt spray are in addition described.