Super effective antimicrobial silver-sputtered coatings on poly(lactic acid) against bacteria and omicron SARS-CoV-2

Poly(lactic acid) (PLA) is a biopolymer with properties potentially suitable for fabricating packaging, medical devices, and healthcare products in a more friendly environmental way because this polymer presents biodegradability, compostability, low carbon footprint, and recyclability. However, PLA does not present intrinsic antimicrobial properties. Antimicrobial materials are highly desirable for manufacturing smart packaging and personal protective equipment to secure food and health professionals against pathogenic microorganisms. In this work, we evaluated the antimicrobial performance of (Ag)-coated PLA against Escherichia coli, Bacillus subtilis, and Omicron severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). PLA was rapidly coated with metallic Ag by pulsed direct current magnetron sputtering (pDCMS) for 5, 10, and 20 s. Atomic force microscopy indicates that the Ag coating grows predominantly on the PLA surface via a bulk diffusion mechanism. According to bactericidal and quantitative reverse transcription polymerase chain reaction assays, Ag-coated PLA was capable of inhibiting bacterial biofilm formation and disrupting the genetic material of the Omicron SARS-CoV-2. X-ray high-resolution photoelectron and nuclear magnetic resonance results suggest no polymer chain scission in the PLA bulk due to plasma thermal stress effects during Ag sputtering. © 2023 Elsevier Ltd

A Bifunctional Spray Coating Reduces Contamination on Surfaces by Repelling and Killing Pathogens.

Surface-mediated transmission of pathogens is a major concern with regard to the spread of infectious diseases. Current pathogen prevention methods on surfaces rely on the use of biocides, which aggravate the emergence of antimicrobial resistance and pose harmful health effects. In response, a bifunctional and substrate-independent spray coating is presented herein. The bifunctional coating relies on wrinkled polydimethylsiloxane microparticles, decorated with biocidal gold nanoparticles to induce a "repel and kill" effect against pathogens. Pathogen repellency is provided by the structural hierarchy of the microparticles and their surface chemistry, whereas the kill mechanism is achieved using functionalized gold nanoparticles embedded on the microparticles. Bacterial tests with methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa reveal a 99.9% reduction in bacterial load on spray-coated surfaces, while antiviral tests with Phi6─a bacterial virus often used as a surrogate to SARS-CoV-2─demonstrate a 98% reduction in virus load on coated surfaces. The newly developed spray coating is versatile, easily applicable to various surfaces, and effective against various pathogens, making it suitable for reducing surface contamination in frequently touched, heavy traffic, and high-risk surfaces.

Aero-manufacture of nanobulges for an in-place anticoronaviral on air filters.

The interest in removing contagious viruses from indoor air using ventilation and filtration systems is increasing rapidly because people spend most of the day indoors. The development of an effective platform to regenerate the antiviral function of air filters during use and safe abrogation of used filters containing infectious viruses is a challenging task, because an on-demand safe-by-design manufacture system is essential for in-place antiviral coatings, but it has been rarely investigated. With these considerations, an electrically operable dispenser was prepared for decorating continuous ultrafine Fe-Zn, Fe-Ag, or Fe-Cu particles (<5 nm) onto SiO2 nanobeads (ca. 130 nm) to form nanobulges (i.e., nanoroughness for engaging coronavirus spikes) in the aerosol state for 3 min direct deposition on the air filter surfaces. The resulting nanobulges were exposed to human coronaviruses (HCoV; surrogates of SARS-CoV-2) to assess antiviral function. The results were compared with similar-sized individual Zn, Ag, and Cu particles. The nanobulges exhibited comparable antiviral activity to Zn, Ag, and Cu particles while retaining biosafety in both in vitro and in vivo models because of the significantly smaller metallic fractions. This suggests that the bimetallic bulge structures generate reactive oxygen species and Fenton-mediated hydroxyl radicals for inactivating HCoV.

Antibacterial and Antiviral Activities of Multi-coating Polyester Textiles

The effect of coated polyester (PET) textiles with metal oxide, chitosan, and copper ion on the antibacterial and antiviral activities was evaluated to investigate the applicability of multi-coated PET textiles as antiviral materials. Compared to coated PETs with a single agent, multi-coated PETs reduced the loading amount of coating materials as well as the contact time with bacteria for a bacterial cell number of < 10 CFU/mL, which was not detectable with the naked eyes. Metal oxides gen-erate reactive oxygen species (ROS) such as free radicals by a catalytic reaction, and copper ions can promote contact killing by the generation of ROS. Chitosan not only enhanced antibacterial activities due to amine groups, but enabled it to be a template to load copper ions. We observed that multi-coated PET textiles have both antibacterial activities for E. coli and S. aureus and antiviral efficiency of more than 99.9% for influenza A (H1N1) and SARS-CoV-2. The multi-coated PET textiles could also be prepared via a roll-to-roll coating process, which showed high antiviral efficacy, demonstrating its potential use in air filtration and antiviral products such as masks and personal protective equipment. © 2022, Korean Society of Industrial Engineering Chemistry. All rights reserved.

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.

Silver Nanoparticles-Polyethyleneimine-Based Coatings with Antiviral Activity against SARS-CoV-2: A New Method to Functionalize Filtration Media.

The use of face masks and air purification systems has been key to curbing the transmission of SARS-CoV-2 aerosols in the context of the current COVID-19 pandemic. However, some masks or air conditioning filtration systems are designed to remove large airborne particles or bacteria from the air, being limited their effectiveness against SARS-CoV-2. Continuous research has been aimed at improving the performance of filter materials through nanotechnology. This article presents a new low-cost method based on electrostatic forces and coordination complex formation to generate antiviral coatings on filter materials using silver nanoparticles and polyethyleneimine. Initially, the AgNPs synthesis procedure was optimized until reaching a particle size of 6.2 ± 2.6 nm, promoting a fast ionic silver release due to its reduced size, obtaining a stable colloid over time and having reduced size polydispersity. The stability of the binding of the AgNPs to the fibers was corroborated using polypropylene, polyester-viscose, and polypropylene-glass spunbond mats as substrates, obtaining very low amounts of detached AgNPs in all cases. Under simulated operational conditions, a material loss less than 1% of nanostructured silver was measured. SEM micrographs demonstrated high silver distribution homogeneity on the polymer fibers. The antiviral coatings were tested against SARS-CoV-2, obtaining inactivation yields greater than 99.9%. We believe our results will be beneficial in the fight against the current COVID-19 pandemic and in controlling other infectious airborne pathogens.

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.

Biodegradable Nanohybrid Materials as Candidates for Self-Sanitizing Filters Aimed at Protection from SARS-CoV-2 in Public Areas.

The COVID-19 pandemic has raised the problem of efficient, low-cost materials enabling the effective protection of people from viruses transmitted through the air or via surfaces. Nanofibers can be a great candidate for efficient air filtration due to their structure, although they cannot protect from viruses. In this work, we prepared a wide range of nanofibrous biodegradable samples containing Ag (up to 0.6 at.%) and Cu (up to 20.4 at.%) exhibiting various wettability. By adjusting the magnetron current (0.3 A) and implanter voltage (5 kV), the deposition of TiO2 and Ag+ implantation into PCL/PEO nanofibers was optimized in order to achieve implantation of Ag+ without damaging the nanofibrous structure of the PCL/PEO. The optimal conditions to implant silver were achieved for the PCL-Ti0.3-Ag-5kV sample. The coating of PCL nanofibers by a Cu layer was successfully realized by magnetron sputtering. The antiviral activity evaluated by widely used methodology involving the cultivation of VeroE6 cells was the highest for PCL-Cu and PCL-COOH, where the VeroE6 viability was 73.1 and 68.1%, respectively, which is significantly higher compared to SARS-CoV-2 samples without self-sanitizing (42.8%). Interestingly, the samples with implanted silver and TiO2 exhibited no antiviral effect. This difference between Cu and Ag containing nanofibers might be related to the different concentrations of ions released from the samples: 80 µg/L/day for Cu2+ versus 15 µg/L/day for Ag+. The high antiviral activity of PCL-Cu opens up an exciting opportunity to prepare low-cost self-sanitizing surfaces for anti-SARS-CoV-2 protection and can be essential for air filtration application and facemasks. The rough cost estimation for the production of a biodegradable nanohybrid PCL-Cu facemask revealed ~$0.28/piece, and the business case for the production of these facemasks would be highly positive, with an Internal Rate of Return of 34%.

Nanocoatings: Universal antiviral surface solution against COVID-19.

In the current scenario, there is critical global demand for the protection of daily handling surfaces from the viral contamination to limit the spread of COVID-19 infection. The nanotechnologists and material scientists offer sustainable solutions to develop antiviral surface coatings for various substrates including fabrics, plastics, metal, wood, food stuffs etc. to face current pandemic period. They create or propose antiviral surfaces by coating them with nanomaterials which interact with the spike protein of SARS-CoV-2 to inhibit the viral entry to the host cell. Such nanomaterials involve metal/metal oxide nanoparticles, hierarchical metal/metal oxide nanostructures, electrospun polymer nanofibers, graphene nanosheets, chitosan nanoparticles, curcumin nanoparticles, etched nanostructures etc. The antiviral mechanism involves the repletion (depletion) of the spike glycoprotein that anchors to surfaces by the nanocoating and makes the spike glycoprotein and viral nucleotides inactive. The nature of interaction between the nanomaterial and virus depends on the type nanostructure coating over the surface. It was found that functional coating materials can be developed using nanomaterials as their polymer nanocomposites. The various aspects of antiviral nanocoatings including the mechanism of interaction with the Corona Virus, the different type of nanocoatings developed for various substrates, future research areas, new opportunities and challenges are reviewed in this article.

Polymeric paint coated common-touch surfaces that can kill bacteria, fungi and influenza virus.

In the current situation of COVID-19 pandemic, the role of surfaces in transmitting pathogens is clearer than ever. Herein, we report an organo-soluble, quaternary antimicrobial paint (QAP) based on polyethyleneimine (PEI) which was coated on a wide range of surfaces such as polyvinylchloride (PVC), nylon, rubber, aluminum. The coating completely killed drug-resistant bacteria. It showed rapid bactericidal properties with complete killing in 45 min of exposure and lowered bacterial adherence, asserting self-sterilizing nature. The coating exhibited complete killing of stationary phase cells of bacteria. The coating killed drug-resistant C. albicans strains. Importantly, QAP coating showed complete killing of influenza virus (H1N1).

Assessment of Antiviral Coatings for High-Touch Surfaces by Using Human Coronaviruses HCoV-229E and SARS-CoV-2.

A novel and robust approach to evaluate the antiviral activity of coatings was developed, assessing three commercially available leave-on surface coating products for efficacy against human coronaviruses (HCoVs) HCoV-229E and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The assessment is based on three criteria that reflect real-life settings, namely, (i) immediate antiviral effect, (ii) effect after repeated cleaning of the coated surface, and (iii) antiviral activity in the presence of organic material. The results showed that only a copper compound-based coating successfully met all three criteria. A quaternary ammonium compound-based coating did not meet the second criterion, and a coating based on reactive oxygen species showed no antiviral effect. Moreover, the study demonstrated that HCoV-229E is a relevant SARS-CoV-2 surrogate for such experiments. This new approach allows benchmarking of currently available antiviral coatings and future coating developments to avoid unjustified claims. The deployment of efficient antiviral coatings can offer an additional measure to mitigate the risk of transmission of respiratory viruses like SARS-CoV-2 or influenza viruses from high-touch surfaces. IMPORTANCE SARS-CoV-2, the virus responsible for the coronavirus disease 2019 (COVID-19) pandemic, is transmitted mainly person-to-person through respiratory droplets, while the contribution of fomite transmission is less important than suspected at the beginning of the pandemic. Nevertheless, antiviral-coating solutions can offer an additional measure to mitigate the risk of SARS-CoV-2 transmission from high-touch surfaces. The deployment of antiviral coatings is not new, but what is currently lacking is solid scientific evidence of the efficacy of commercially available self-disinfecting surfaces under real-life conditions. Therefore, we developed a novel, robust approach to evaluate the antiviral activity of such coatings, applying strict quality criteria to three commercially available products to test their efficacies against SARS-CoV-2. We also showed that HCoV-229E is a relevant surrogate for such experiments. Our approach will also bring significant benefit to the evaluation of the effects of coatings on the survival of nonenveloped viruses, which are known to be more tolerant to desiccation and disinfectants and for which high-touch surfaces play an important role.

Efficacy of an antimicrobial surface coating against human coronavirus 229E and SARS-CoV-2.

The COVID-19 pandemic has accelerated the demand for alternatives to standard cleaning and disinfection practices. Antiviral coatingsmay provide an alternative to common surface treatments. A newly developed quaternary ammonium polymer coating was applied to stainless steel coupons and evaluated for efficacy against human coronavirus 229E and SARS-CoV-2. The polymer coating reduced levels of both test viruses by greater than 99.9% relative to non-coated stainless steel coupons during a 2-hour contact time.