N-Halamine-modified antimicrobial polypropylene nonwoven fabrics for use against airborne bacteria

Facile Synthesis of Cu-Doped TiO2 Particles for Accelerated Visible Light-Driven Antiviral and Antibacterial Inactivation

In this work, we present a facile and scalable hydrolysis-based route for the synthesis of copper-doped TiO2 particles for highly effective light-activated antiviral and antibacterial applications. The performance of the synthesized Cu-doped TiO2 particles is then evaluated using solution-phase antimicrobial photodynamic inactivation assays. We demonstrate that the Cu-doped TiO2 particles can successfully inactivate a wide range of pathogens with exposure to light for 90 min, including bacteria ranging from methicillin-resistant Staphylococcus aureus (99.9999%, ∼6 log units) to Klebsiella pneumoniae (99.93%, ∼3.3 log units), and viruses including feline calicivirus (99.94%, ∼3.4 log units) and HCoV-229E (99.996%, ∼4.6 log units), with the particles demonstrating excellent robustness toward photobleaching. Furthermore, a spray-coated polymer film, loaded with the synthesized Cu-doped TiO2 particles achieves inactivation of methicillin-resistant S. aureus up to 99.998% (∼4.8 log units). The presented results provide a clear advance forward in the use of metal-doped TiO2 for aPDI applications, including the scalable synthesis (kg/day) of well-characterized and robust particles, their facile incorporation into a nontoxic, photostable coating that may be easily and cheaply applied to a multitude of surfaces, and a broad efficacy against drug-resistant Gram-positive and Gram-negative bacteria, as well as against enveloped and nonenveloped viruses.

Nanofiberous facemasks as protectives against pandemic respiratory viruses

INTRODUCTION

Wearing protective face masks and respirators has been a necessity to reduce the transmission rate of respiratory viruses since the outbreak of the coronavirus (COVID-19) disease. Nevertheless, the outbreak has revealed the need to develop efficient air filter materials and innovative anti-microbial protectives. Nanofibrous facemasks, either loaded with antiviral nanoparticles or not, are very promising personal protective equipment (PPE) against pandemic respiratory viruses.

AREAS COVERED

In this review, multiple types of face masks and respirators are discussed as well as filtration mechanisms of particulates. In this regard, the limitations of traditional face masks were summarized and the advancement of nanotechnology in developing nanofibrous masks and air filters was discussed. Different methods of preparing nanofibers were explained. The various approaches used for enhancing nanofibrous face masks were covered.

EXPERT OPINION

Although wearing conventional face masks can limit viral infection spread to some extent, the world is in great need for more protective face masks. Nanofibers can block viral particles efficiently and can be incorporated into face masks in order to enhance their filtration efficiency. Also, we believe that other modifications such as addition of antiviral nanoparticles can significantly increase the protection power of facemasks.

Nonleaching Biocidal N-Halamine-Functionalized Polyamine-, Guanidine-, and Hydantoin-Based Coatings

Fibrous materials with inherent antimicrobial properties can help in real-time deactivation of microorganisms, enabling multiple uses while reducing secondary infections. Coatings with antiviral polymers enhance the surface functionality for existing and potential future pandemics. Herein, we demonstrated a straightforward route toward biocidal surface creation using polymers with nucleophilic biguanide, guanidine, and hydantoin groups that are covalently attached onto a solid support. Biocidal poly(N-vinylguanidine) (PVG) and poly(allylamine-co-4-aminopyridine-co-5-(4-hydroxybenzylidene)hydantoin) (PAH) were introduced for coating applications along with commercially available polyvinylamine (PVAm) and poly(hexamethylene biguanide) (PHMB). Nonleaching coatings were created by first fabricating bifunctional siloxane or isocyanate precursor coatings on the cotton, nylon-cotton, and glass fiber fabric, followed by the polymer attachment. The developed grafting methods ensured the stability of the coating and the reuse of the material while maintaining the biocidal properties. Halogenation of polymer-coated fabric was conducted by aqueous solutions of sodium hypochlorite or in situ generation of hypobromous acid (HOBr), resulting in surfaces coated by N-halamines with high contents of active > N-Cl or > N-Br groups. The polymer-coated fabrics were stable in multiple laundry cycles and maintained hydrophilic character after coating and halogenation. Halogenated polymer-coated fabrics completely inactivated human respiratory coronavirus based on a contact-killing mechanism and were shown to be reusable after recharging with bromine or chlorine.

Preparation of Rechargeable Antibacterial Polypropylene/N-Halamine Materials Based on Melt Blending and Surface Segregation

Polypropylene (PP) has been widely used in health care and food packaging fields, however, it lacks antibacterial properties. Herein, we prepared the polymeric antibacterial agents (MPP-NDAM) by an in situ amidation reaction between 2,4-diamino-6-dialkylamino-1,3,5-triazine (NDAM) and maleic anhydride grafted polypropylene (MPP) using the melt grafting method. The effects of reaction time and monomer content on the grafting degree of N-halamine were investigated, and a grafting degree of 4.86 wt % was achieved under the optimal reaction conditions. PP/MPP-NDAM composites were further obtained by a melt blending process between PP and MPP-NDAM. With the adoption of surface segregation technology, the content of N-halamine structure on the surface of PP/MPP-NDAM composites was significantly increased. The antibacterial tests showed that the PP/MPP-NDAM composite could achieve 99.9% bactericidal activity against 1.0 × 107 CFU/mL of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) within 10 and 5 min of contact, respectively. The antibacterial effect became more pronounced with the prolongation of chlorinated time, and it could achieve 99.9% bactericidal activity against E. coli within merely 1 min of contact.

Antibacterial Mesoporous Silica Granules Containing a Stable N-Halamine Moiety

High-efficacy and regenerable antimicrobial silica granules were prepared via oxa-Michael addition between poly(vinyl alcohol) (PVA) and methylene-bis-acrylamide (MBA) under the catalysis of sodium carbonate in an aqueous solution. Diluted water glass was added, and the solution pH was adjusted to about 7 to precipitate PVA-MBA modified mesoporous silica (PVA-MBA@SiO₂) granules. N-Halamine-grafted silica (PVA-MBA-Cl@SiO₂) granules were achieved by adding diluted sodium hypochlorite solution. It was found that a BET surface area of about 380 m² g^-1 for PVA-MBA@SiO₂ granules and a Cl⁺% of about 3.80% for PVA-MBA-Cl@SiO₂ granules could be achieved under optimized preparation conditions. Antimicrobial tests showed that the as-prepared antimicrobial silica granules were capable of about a 6-log inactivation of Staphylococcus aureus and Escherichia coli O157:H7 within 10 min of contact. Furthermore, the as-prepared antimicrobial silica granules can be recycled many times due to the excellent regenerability of their N-halamine functional groups and can be saved for a long time. With the above-mentioned advantages, the granules have potential applications in water disinfection.

Electrospinning in personal protective equipment for healthcare work

Protection in many service areas is mandatory for good performance in daily activities of workers, especially health areas. Personal protective equipment (PPE) is used to protect patients and health workers from contamination by harmful pathogens and body fluids during clinical attendance. The pandemic scenario caused by SARS-CoV-2 has shown that the world is not prepared to face global disease outbreaks, especially when it comes to the PPE of healthcare workers. In the last years, the world has faced a deficiency in the development of advanced technologies to produce high-quality PPE to attend to the exponential increasing demand. Electrospinning is a technology that can be used to produce high-quality PPE by improving the protective action of clothing. In the face of this concern, this manuscript presents as focus the potential of electrospinning to be applied in protective clothing. PPE mostly used by healthcare workers are also presented. The physico-chemical characteristics and production processes of medical textiles for PPE are addressed. Furthermore, an overview of the electrospinning technique is shown. It is important to highlight most research about electrospinning applied to PPE for health areas presents gaps and challenges; thus, future projections are also addressed in this manuscript.

Zwitterion and N-halamine functionalized cotton wound dressing with enhanced antifouling, antibacterial, and hemostatic properties

With emerging needs of wound care management, a multi-functional wound dressing is needed. To prevent infection and reduce patient suffering, antibacterial efficacy against a broad-spectrum of bacteria plus robust antifouling are among the most preferred properties. In this study, a wound dressing was created with antibacterial and anti-fouling capabilities is presented. The approaches used a synthesized tri-functional copolymer comprised of an N-halamine precursor moiety, a marine-inspired surface binding dopamine moiety, and a zwitterionic anti-adhesion moiety bonded onto a commercial cotton gauze. The resulting HaloCare™ wound dressing demonstrated >99.99 % inactivation within 5 min against E. coli and a panel of ESKAPE pathogens plus achieved 98.77 % reduction of non-specific protein binding. HaloCare was also shown to be compatible with hemostatic agents without impacting hemostatic efficacy. HaloCare shows great potential particularly in traumatic injury events as an infection preventing and hemostatic wound management system.

N-halamine surface coating for mitigation of biofilm and microbial contamination in water systems for space travel

A copolymer termed HASL produced from monomeric units of 2-acrylamido-2-methyl-1-(5-methylhydantoinyl)propane (HA) and of 3-(trimethoxysilyl)propyl methacrylate (SL) has been coated onto stainless steel and Inconel™ substrates, which upon halogenation with either aqueous oxidative chlorine or bromine, became antimicrobial. It has been demonstrated that the halogenated stainless steel and Inconel™ substrates were effective in producing 6 to 7 log inactivations of Staphylococcus aureus and Escherichia coli O157:H7 within about 10 min, and in prevention of Pseudomonas aeruginosa biofilm formation over a period of at least 72 h on the stainless steel substrates. Upon loss of halogen, the HASL coating could be re-charged with aqueous halogen. The HASL coating was easily applied to the substrates via a simple dip-coating method and was reasonably stable to contact with water. Both chlorinated substrates could be loaded with at least 6 × 1016 oxidative Cl atoms per cm2 and maintained a loading of greater than 1 × 1016 chlorine atoms per cm2 for a period of 3-7 days while agitated in aqueous solution. After loss of chlorine to a level below 1 × 1016 atoms per cm2, the substrates could be recharged to the 6 × 1016 Cl atoms per cm2 level for at least 5 times over a 28 day period. The new antimicrobial coating technology has potential for use in a variety of important applications, particularly for water treatment and storage on spacecraft.

Surface antimicrobial functionalization with polymers: fabrication, mechanisms and applications

Undesirable adhesion of microbes such as bacteria, fungi and viruses onto surfaces affects many industries such as marine, food, textile, and healthcare. In particular in healthcare and food packaging, the effects of unwanted microbial contamination can be life-threatening. With the current global COVID-19 pandemic, interest in the development of surfaces with superior anti-viral and anti-bacterial activities has multiplied. Polymers carrying anti-microbial properties are extensively used to functionalize material surfaces to inactivate infection-causing and biocide-resistant microbes including COVID-19. This review aims to introduce the fabrication of polymer-based antimicrobial surfaces through physical and chemical modifications, followed by the discussion of the inactivation mechanisms of conventional biocidal agents and new-generation antimicrobial macromolecules in polymer-modified antimicrobial surfaces. The advanced applications of polymer-based antimicrobial surfaces on personal protective equipment against COVID-19, food packaging materials, biomedical devices, marine vessels and textiles are also summarized to express the research trend in academia and industry.

Advances in nanotechnology application in biosafety materials: A crucial response to COVID-19 pandemic

The outbreak of coronavirus disease 2019 (COVID-19) has adversely affected the public domain causing unprecedented cases and high mortality across the globe. This has brought back the concept of biosafety into the spotlight to solve biosafety problems in developing diagnostics and therapeutics to treat COVID-19. The advances in nanotechnology and material science in combination with medicinal chemistry have provided a new perspective to overcome this crisis. Herein, we discuss the efforts of researchers in the field of material science in developing personal protective equipment (PPE), detection devices, vaccines, drug delivery systems, and medical equipment. Such a synergistic approach of disciplines can strengthen the research to develop biosafety products in solving biosafety problems.

Antimicrobial Nonwoven Fabrics Incorporated with Levulinic Acid and Sodium Dodecyl Sulfate for Use in the Food Industry

Safe and cost-effective antimicrobial fabrics (e.g., face masks and air filters) are conducive to preventing the spread and transmission of respiratory microorganisms in food processing plants and retail establishments. The objective of this study was to coat fabrics with two commonly used compounds in the food industry: levulinic acid (LVA) and sodium dodecyl sulfate (SDS) and determine the antimicrobial efficacy of the coated fabrics against bacterial solutions, aerosols, and influenza A virus subtype H1N1. In addition, air permeability and shelf-life of the LVA/SDS coated fabrics were also examined. Nonwoven fabrics were dip-coated with three concentrations (w/v, 0.5% LVA + 0.1% SDS, 1% LVA + 0.5% SDS, and 2% LVA + 1% SDS) of LVA and SDS and challenged with bacterial solutions (Staphylococcus aureus and Escherichia coli, ca. 7.0 log CFU/coupon) for a contact time of 3, 5, and 10 min. The coated fabrics were also challenged with S. aureus aerosol and H1N1 virus following standard operations of ASTM F2101-19 and ISO 18184:2019, respectively. The 1% LVA + 0.5% SDS coated fabrics showed potent antibacterial efficacy against both bacterial solutions (>6.0-log reduction to under the detection limit of 1.0 log CFU/coupon for S. aureus; ca. 1.0-log reduction for E. coli) and aerosols (>3.6-log reduction to under the detection limit), with greater inactivation occurring at higher concentrations and longer exposure time. Moreover, the coated fabrics inactivated >99% of the H1N1 virus. The shelf-life of the coated fabrics was stable within 12 months and the air permeability was not adversely affected with the coating concentrations less than 1% LVA + 0.5% SDS. Results reveal these low-cost and safe materials have the potential to be used to coat fabrics in the food industry to combat the spread and transmission of pathogens.

A Sustainable and Antimicrobial Food Packaging Film for Potential Application in Fresh Produce Packaging

N-halamines are a group of compounds containing one or more nitrogen-halogen covalent bond(s). This high-energy halide bond provides a strong oxidative state so that it is able to inactivate microorganisms effectively. In this study, a sustainable film was developed based on polylactic acid (PLA) with incorporated N-halamine compound 1-chloro-2,2,5,5-tetramethyl-4-imidazolidinone (MC), as a promising antimicrobial food packaging material. Results showed that the incorporation of MC prevented the crystallization of PLA and improved the physical properties of the films. In addition, both the moisture barrier and the oxygen permeability were improved with the presence of MC. Importantly, the antimicrobial film was able to inactivate inoculated microorganisms by a factor of seven log cycles in as little as 5 min of contact. Films that contained higher levels of MC further enhanced the antimicrobial efficacy. Fresh strawberries packed with the fabricated films maintained the quality for up to 5 days. Due to the ease of fabrication and the effective biocidal property, these films have a wide range of potential applications in the field of food packaging to extend the shelf life of fresh produce.

How to Make Personal Protective Equipment Spontaneously and Continuously Antimicrobial (Incorporating Oxidase-like Catalysts)

The inability of commercial personal protective equipment (PPE) to inactivate microbes in the droplets/aerosols they intercept makes used PPE a potential source of cross-contamination. To make PPE spontaneously and continuously antimicrobial, we incorporate PPE with oxidase-like catalysts, which efficiently convert O₂ into reactive oxygen species (ROS) without requiring any externally applied stimulus. Using a single-atom catalyst (SAC) nanoparticle containing atomically dispersed copper atoms as the reactive centers (Cu-SAC) and a silver-palladium bimetallic alloy nanoparticle (AgPd_0.38) as models for oxidase-like catalysts, we show that the incorporation of oxidase-like catalysts enables PPE to inactivate bacteria in the droplets/aerosols they intercept without requiring any externally applied stimulus. Notably, this approach works both for PPE that are fibrous and woven such as a commercial KN95 facial respirator and for those made of solid plastics such as an apron. This work suggests a feasible and global approach for preventing PPE from spreading infectious diseases.

Photosensitized Electrospun Nanofibrous Filters for Capturing and Killing Airborne Coronaviruses under Visible Light Irradiation

To address the challenge of the airborne transmission of SARS-CoV-2, photosensitized electrospun nanofibrous membranes were fabricated to effectively capture and inactivate coronavirus aerosols. With an ultrafine fiber diameter (∼200 nm) and a small pore size (∼1.5 μm), optimized membranes caught 99.2% of the aerosols of the murine hepatitis virus A59 (MHV-A59), a coronavirus surrogate for SARS-CoV-2. In addition, rose bengal was used as the photosensitizer for membranes because of its excellent reactivity in generating virucidal singlet oxygen, and the membranes rapidly inactivated 97.1% of MHV-A59 in virus-laden droplets only after 15 min irradiation of simulated reading light. Singlet oxygen damaged the virus genome and impaired virus binding to host cells, which elucidated the mechanism of disinfection at a molecular level. Membrane robustness was also evaluated, and in general, the performance of virus filtration and disinfection was maintained in artificial saliva and for long-term use. Only sunlight exposure photobleached membranes, reduced singlet oxygen production, and compromised the performance of virus disinfection. In summary, photosensitized electrospun nanofibrous membranes have been developed to capture and kill airborne environmental pathogens under ambient conditions, and they hold promise for broad applications as personal protective equipment and indoor air filters.

Advancing Strategies of Biofouling Control in Water-Treated Polymeric Membranes

Polymeric membranes, such as polyamide thin film composite membranes, have gained increasing popularity in wastewater treatment, seawater desalination, as well as the purification and concentration of chemicals for their high salt-rejection and water flux properties. Membrane biofouling originates from the attachment or deposition of organic macromolecules/microorganisms and leads to an increased operating pressure and shortened service life and has greatly limited the application of polymeric membranes. Over the past few years, numerous strategies and materials were developed with the aim to control membrane biofouling. In this review, the formation process, influence factors, and consequences of membrane biofouling are systematically summarized. Additionally, the specific strategies for mitigating membrane biofouling including anchoring of hydrophilic monomers, the incorporation of inorganic antimicrobial nanoparticles, coating/grafting of cationic bactericidal polymers, and the design of multifunctional material integrated multiple anti-biofouling mechanisms, are highlighted. Finally, perspectives on the challenges and opportunities in anti-biofouling polymeric membranes are shared, shedding light on the development of even better anti-biofouling materials in near future.

Cost-effective fabrication, antibacterial application and cell viability studies of modified nonwoven cotton fabric

In the present work, nonwoven cotton fabric was modified for antibacterial applications using low-cost and eco-friendly precursors. The treatment of fabric with alkali leads to the formation of active sites for surface modification, followed by dip coating with silver nanoparticles and chitosan. The surface was chlorinated in the next step to transform amide (N-H) groups in chitosan into N-halamine (N-Cl). The modified and unmodified surfaces of the nonwoven cotton fabric have been characterized by FTIR, SEM, and XRD. The active chlorine loading is measured with iodine/sodium thiosulphate. The antimicrobial activity and cell toxicity assay were carried out with and without modifications of nonwoven cotton fabric. The antimicrobial efficacies of loaded fabric were evaluated against four bacterial species (Micrococcus luteus, Staphylococcus aureus, Enterobacter aerogenes, and E.coli). It was found that modified fabric exhibited superior efficiency against gram-positive and gram-negative bacterial strains as compared to their bulk counterparts upon exposure without affecting strength and integrity of fabric. The overall process is economical for commercial purposes. The modified fabric can be used for antimicrobial, health, and food packaging industries, and in other biomedical applications.

Ag/Zn Galvanic Couple Cotton Nonwovens with Breath-Activated Electroactivity: A Possible Antibacterial Layer for Personal Protective Face Masks

The water vapor exhaled by the human body can severely accelerate the charge dissipation of commercial face masks, thereby reducing the electrostatic adsorption efficiency and increasing the bacterial invasion risk. This study developed an electroactive antibacterial cotton nonwoven (Ag/cotton/Zn) using eco-friendly magnetron sputtering technology. The Ag/Zn electrode constructed on the surface of cotton nonwovens could produce a microelectric field in the moist environment of human respiration, which endowed Ag/cotton/Zn with excellent electroactivity. When Ag/cotton/Zn was used as an additional layer of polypropylene melt-blown nonwovens or polylactic acid nanofibers, the prepared personal protective air filter had a filtration efficiency of up to 96.8% and an appropriate pressure drop and air permeability. The antibacterial results based on bacterial aerosols showed that the antibacterial efficiency against Escherichia coli and Staphylococcus aureus in 20 min was 99.74 and 99.79%, respectively, indicating an excellent electroactive killing efficiency against airborne bacteria. In addition, Ag/cotton/Zn showed excellent biological security. These results shed some light on the design and fabrication of next generation of personal protective air filter materials driven by human breathing.

Biodegradable and multifunctional surgical face masks: A brief review on demands during COVID-19 pandemic, recent developments, and future perspectives

Providing the greater public with the current coronavirus (SARS-CoV-2) vaccines is time-consuming and research-intensive; intermediately, some essential ways to reduce the transmission include social distancing, personal hygiene, testing, contact tracing, and universal masking. The data suggests that universal masking, especially using multilayer surgical face masks, offers a powerful efficacy for indoor places. These layers have different functions including antiviral/antibacterial, fluid barrier, particulate and bacterial filtration, and fit and comfort. However, universal masking poses a serious environmental threat since billions of them are disposed on a daily basis; the current coronavirus disease (COVID-19) has put such demands and consequences in perspective. This review focuses on surgical face mask structures and classifications, their impact on our environment, some of their desirable functionalities, and the recent developments around their biodegradability. The authors believe that this review provides an insight into the fabrication and deployment of effective surgical face masks, and it discusses the utilization of multifunctional structures along with biodegradable materials to deal with future demands in a more eco-friendly fashion.

Materials in advanced design of personal protective equipment: a review

The outbreak of the Covid-19 pandemic has aroused tremendous attention toward personal protective equipment (PPE) in both scientific research and industrial manufacture. Despite decades of development in PPE design and fabrication, there's still much room for further optimization, in terms, of both protection performance and wear comfort. Interdisciplinary efforts have been devoted to this research field in recent years. Significantly, the innovation of materials, which brings about improved performance and versatile new functions for PPEs, has been widely adopted in PPE design. In this minireview, recent progress in the development of novel materials and structural designs for PPE application are presented in detail with the introduction of various material-based strategies for different PPE types, as well as the examples, which apply auxiliary components into face masks to enrich the functionalities and improve the personal feelings in the pandemic period.

A natural polysaccharide-based antibacterial functionalization strategy for liquid and air filtration membranes

Filtration membranes are widely applied in medical fields. However, these membranes are challenged by bacterial contamination in hospitals, which increases the risk of nosocomial infections. Thus, it is significant to develop antibacterial filtration membranes. In this work, an oxidated dextran (ODex)-based antibacterial coating was designed and constructed on microfiltration (MF) membranes and melt-blown fabrics. Polyhexamethylene guanidine (PHMG) was synthesized as an antibacterial agent, and was fixed by ODex onto filtration membranes. The functionalized MF membranes increased the filtration efficiency for E. coli from 20.9% to 99.9%, and improved the absorption ratio for endotoxin by 59.1%, while the water flow rate still remained as high as 5255 L (h m²)^-1. Furthermore, the trapped bacteria were inactivated by the antibacterial coating. For the melt-blown fabrics, the aerosol filtration efficiency was increased from 74.6% to 81.0%, and the antibacterial efficiency was promoted to 92.0%. The present work developed a facile and universal antibacterial functionalization strategy for filtration membranes, which provided a new method for the design and development of various novel antibacterial filtration materials in the medical field.

Recent Progress in Modified Polymer-Based PPE in Fight Against COVID-19 and Beyond

The increasing concerns about human-health-related microbial infections and the need for the development of personal protective equipment (PPE) is becoming a major challenge. Because of their light weight and ease of processing, polymeric materials are widely used in designing and fabricating PPE that are being used by healthcare workers and the general population. Among the available PPEs, face masks have been widely developed from polymeric materials such as polypropylene, polycarbonate, and poly(ethylene terephthalate). However, currently, many of the face masks are not antimicrobial, which can pose a great risk for cross-infection as discarded masks can be a dangerous source of microbes. To prevent the spread of microbes, researchers have prompted the development of self-sterilizing masks that are capable of inactivating microbes via different mechanisms. Hence, this review provides a brief overview of the currently available antimicrobial-modified polymer-based PPE, and it mainly focuses on the different types of nanoparticles and other materials that have been embedded in different polymeric materials. The possibility of inhaling microplastics from wearing a face mask is also outlined, and the effects of various modifications on the health of face mask users are also explored. Furthermore, the effects of the disposed masks on the environment are underlined.

Enhanced Medical and Community Face Masks with Antimicrobial Properties: A Systematic Review

Face masks help to limit transmission of infectious diseases entering through the nose and mouth. Beyond reprocessing and decontamination, antimicrobial treatments could extend the lifetime of face masks whilst also further reducing the chance of disease transmission. Here, we review the efficacy of treatments pertaining antimicrobial properties to medical face masks, filtering facepiece respirators and non-medical face masks. Searching databases identified 2113 studies after de-duplication. A total of 17 relevant studies were included in the qualitative synthesis. Risk of bias was found to be moderate or low in all cases. Sixteen articles demonstrated success in avoiding proliferation (if not elimination) of viruses and/or bacteria. In terms of methodology, no two articles employed identical approaches to efficacy testing. Our findings highlight that antimicrobial treatment is a promising route to extending the life and improving the safety of face masks. In order to reach significant achievements, shared and precise methodology and reporting is needed.

Incorporation of Antimicrobial Bio-Based Carriers onto Poly(vinyl alcohol-co-ethylene) Surface for Enhanced Antimicrobial Activity

A biobased rechargeable antimicrobial modification approach was developed using a covalent immobilization of food grade yeast cell wall particles on a model plastic film. We demonstrate the applications of this modification approach on poly(vinyl alcohol-co-ethylene) surface to inactivate inoculated bacteria with or without the presence of organic content, reducing the cross-contamination between food contact surface and model fresh produce, and inhibiting the growth of biofilms on the film surface. These biobased cell wall particle modified plastic films can enhance the binding of chlorine to the plastic surface in the form of N-halamine, extend the stability of chlorine against high organic content and ambient storage, and improve the rechargeability of the plastic films. Upon charging with chlorine, these modified plastic films inactivated 5 log of model Gram-negative bacteria (Escherichia coli O157:H7) and Gram-positive bacteria (Listeria innocua used as a surrogate of pathogenic Listeria monocytogenes) within 2 min of surface inoculation in water and within 20 min in an organic-rich aqueous environment. The modified plastic films prevented the transfer of bacteria and eliminated cross-contamination from the contaminated films to a spinach leaf surface, while 3 log CFU/leaf of bacteria were transferred from a contaminated native film to a noninoculated spinach surface. In addition, these modified plastic films reduced the adhesion of L. innocua cells by 2.7-3.6 log CFU/cm² compared with control films during extended incubation for biofilm formation. Overall, this study demonstrates the feasibility of this biobased food grade modification approach to reduce microbial contamination and improve produce safety in the food processing industry.

Toward Universal Photodynamic Coatings for Infection Control

The dual threats posed by the COVID-19 pandemic and hospital-acquired infections (HAIs) have emphasized the urgent need for self-disinfecting materials for infection control. Despite their highly potent antimicrobial activity, the adoption of photoactive materials to reduce infection transmission in hospitals and related healthcare facilities has been severely hampered by the lack of scalable and cost-effective manufacturing, in which case high-volume production methods for fabricating aPDI-based materials are needed. To address this issue here, we examined the antimicrobial efficacy of a simple bicomponent spray coating composed of the commercially-available UV-photocrosslinkable polymer N-methyl-4(4'-formyl-styryl)pyridinium methosulfate acetal poly(vinyl alcohol) (SbQ-PVA) and one of three aPDI photosensitizers (PSs): zinc-tetra(4-N-methylpyridyl)porphine (ZnTMPyP⁴⁺), methylene blue (MB), and Rose Bengal (RB). We applied these photodynamic coatings, collectively termed SbQ-PVA/PS, to a variety of commercially available materials. Scanning electron microscopy (SEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) confirmed the successful application of the coatings, while inductively coupled plasma-optical emission spectroscopy (ICP-OES) revealed a photosensitizer loading of 0.09-0.78 nmol PS/mg material. The antimicrobial efficacy of the coated materials was evaluated against methicillin-susceptible Staphylococcus aureus ATCC-29213 and human coronavirus strain HCoV-229E. Upon illumination with visible light (60 min, 400-700 nm, 65 ± 5 mW/cm²), the coated materials inactivated S. aureus by 97-99.999% and HCoV-229E by 92-99.999%, depending on the material and PS employed. Photobleaching studies employing HCoV-229E demonstrated detection limit inactivation (99.999%) even after exposure for 4 weeks to indoor ambient room lighting. Taken together, these results demonstrate the potential for photodynamic SbQ-PVA/PS coatings to be universally applied to a wide range of materials for effectively reducing pathogen transmission.

Cow dung-derived biochars engineered as antibacterial agents for bacterial decontamination

Disposal of the pollutants arising from farming cattle and other livestock threatens the environment and public safety in diverse ways. Herein, we report on the synthesis of engineered biochars using cow dung as raw material, and investigating these biochars as antibacterial agents for water decontamination. By coating the biochars with N-halamine polymer and loading them with active chlorine (i.e., Cl⁺), we were able to regulate them on demand by tuning the polymer coating and bleaching conditions. The obtained N-halamine-modified biochars were found to be extremely potent against Escherichia coli and Staphylococcus aureus. We also investigated the possibility of using these N-halamine-modified biochars for bacterial decontamination in real-world applications. Our findings indicated that a homemade filter column packed with N-halamine-modified biochars removed pathogenic bacteria from mining sewage, dairy sewage, domestic sewage, and artificial seawater. This proposed strategy could indicate a new way for utilizing livestock pollutants to create on-demand decontaminants.

Ultrathin Polydopamine-Graphene Oxide Hybrid Coatings on Polymer Filters with Improved Filtration Performance and Functionalities

Thin polymer fiber mats, in particular those made of nonwoven polypropylene (PP) fibers, are extensively used for medical and industrial filtration. The recent pandemic has increased the demand for the fabrication of protective masks. The nonwoven PP filter has limitations in filtration efficiency and lacks advanced functionalities. Here, we propose a simple, effective, and low-cost method to functionalize PP filters and endow antimicrobial and photothermal properties. Our approach is based on the deposition of an ultrathin hybrid coating composed of graphene oxide (GO) and polydopamine on the surface of PP filters by spray-coating. The complementary properties and synergic effects of GO and polydopamine in the ultrathin coating improved the filtration efficiency of the PP filter by 20% with little change in pressure drop. Single component coatings did not result in similar improvements in performance. The ultrathin coating also makes the surface of the filter more hydrophilic with negative charges. The photothermal property of GO enables a rapid temperature increase of the surface-coated filter upon light irradiation for easy sterilization. Furthermore, cationic polymer brushes can be grafted to the ultrathin hybrid coating, which adds the highly desired antimicrobial property to the PP filters for their more effective protection against microorganisms.

Antimicrobial Polymer-Based Assemblies: A Review

An antimicrobial supramolecular assembly (ASA) is conspicuous in biomedical applications. Among the alternatives to overcome microbial resistance to antibiotics and drugs, ASAs, including antimicrobial peptides (AMPs) and polymers (APs), provide formulations with optimal antimicrobial activity and acceptable toxicity. AMPs and APs have been delivered by a variety of carriers such as nanoparticles, coatings, multilayers, hydrogels, liposomes, nanodisks, lyotropic lipid phases, nanostructured lipid carriers, etc. They have similar mechanisms of action involving adsorption to the cell wall, penetration across the cell membrane, and microbe lysis. APs, however, offer the advantage of cheap synthetic procedures, chemical stability, and improved adsorption (due to multipoint attachment to microbes), as compared to the expensive synthetic routes, poor yield, and subpar in vivo stability seen in AMPs. We review recent advances in polymer-based antimicrobial assemblies involving AMPs and APs.

Antibacterial and Antiviral Functional Materials: Chemistry and Biological Activity toward Tackling COVID-19-like Pandemics

The ongoing worldwide pandemic due to COVID-19 has created awareness toward ensuring best practices to avoid the spread of microorganisms. In this regard, the research on creating a surface which destroys or inhibits the adherence of microbial/viral entities has gained renewed interest. Although many research reports are available on the antibacterial materials or coatings, there is a relatively small amount of data available on the use of antiviral materials. However, with more research geared toward this area, new information is being added to the literature every day. The combination of antibacterial and antiviral chemical entities represents a potentially path-breaking intervention to mitigate the spread of disease-causing agents. In this review, we have surveyed antibacterial and antiviral materials of various classes such as small-molecule organics, synthetic and biodegradable polymers, silver, TiO2, and copper-derived chemicals. The surface protection mechanisms of the materials against the pathogen colonies are discussed in detail, which highlights the key differences that could determine the parameters that would govern the future development of advanced antibacterial and antiviral materials and surfaces.

A comprehensive review on antimicrobial face masks: an emerging weapon in fighting pandemics

The world has witnessed several incidents of epidemics and pandemics since the beginning of human existence. The gruesome effects of microbial threats create considerable repercussions on the healthcare systems. The continually evolving nature of causative viruses due to mutation or re-assortment sometimes makes existing medicines and vaccines inactive. As a rapid response to such outbreaks, much emphasis has been placed on personal protective equipment (PPE), especially face mask, to prevent infectious diseases from airborne pathogens. Wearing face masks in public reduce disease transmission and creates a sense of community solidarity in collectively fighting the pandemic. However, excessive use of single-use polymer-based face masks can pose a significant challenge to the environment and is increasingly evident in the ongoing COVID-19 pandemic. On the contrary, face masks with inherent antimicrobial properties can help in real-time deactivation of microorganisms enabling multiple-use and reduces secondary infections. Given the advantages, several efforts are made incorporating natural and synthetic antimicrobial agents (AMA) to produce face mask with enhanced safety, and the literature about such efforts are summarised. The review also discusses the literature concerning the current and future market potential and environmental impacts of face masks. Among the AMA tested, metal and metal-oxide based materials are more popular and relatively matured technology. However, the repeated use of such a face mask may pose a danger to the user and environment due to leaching/detachment of nanoparticles. So careful consideration is required to select AMA and their incorporation methods to reduce their leaching and environmental impacts. Also, systematic studies are required to establish short-term and long-term benefits.

Air-Filtering Masks for Respiratory Protection from PM2.5 and Pandemic Pathogens

Air-filtering masks, also known as respirators, protect wearers from inhaling fine particulate matter (PM2.5) in polluted air, as well as airborne pathogens during a pandemic, such as the ongoing COVID-19 pandemic. Fibrous medium, used as the filtration layer, is the most essential component of an air-filtering mask. This article presents an overview of the development of fibrous media for air filtration. We first synthesize the literature on several key factors that affect the filtration performance of fibrous media. We then concentrate on two major techniques for fabricating fibrous media, namely, meltblown and electrospinning. In addition, we underscore the importance of electret filters by reviewing various methods for imparting electrostatic charge on fibrous media. Finally, this article concludes with a perspective on the emerging research opportunities amid the COVID-19 crisis.

Supercritical carbon dioxide application using hydantoin acrylamide for biocidal functionalization of polyester

Biocidal functionalization in polyester fibers is a really tough challenge because of the lack of tethering groups. This study indicated supercritical carbon dioxide application using N-halamine would be an alternative solution for obtaining antibacterial function on the polyester surface. Firstly, N-(2-methyl-1-(4-methyl-2,5-dioxo-imidazolidin-4 yl)propan-2 yl)acrylamide was synthesized and applied to the polyester in supercritical carbon dioxide medium, at 120 °C, 30 MPa for different processing times. The addition of N-halamine on the surface significantly brought antibacterial activity against E. coli. The chlorine loadings showed that 6 -h exposure time was critical to obtain sufficient antibacterial activity. This treatment caused a reasonable and tolerable loss in color and mechanical properties. But, the durability to abrasion, stability, and rechargeability of oxidative chlorine, and the durability of N-halamine on the surface were remarkably good. Conclusively, it can be available to work on polyester surfaces with resource-efficient and eco-friendly supercritical carbon dioxide technique for getting more functionalization and modification.

Novel porous chitosan/N-halamine structure with efficient antibacterial and hemostatic properties

In this work, a novel chitosan based structure (CS/EVC) with low density, high porosity, three-dimensional porous structure and great adsorption capability has been prepared by using 1,2-epoxy-4-vinyl cyclohexane (EVC) as a cross-linker. After immersing CS/EVC in N-halamine 1-chloro-2,2,5,5-tetramethyl-4-imidazolinone (MC) solution, antibacterial CS/EVC/MC compounds were obtained. Compared with chitosan and CS/EVC controls, CS/EVC/MC showed excellent antimicrobial activities, which could inactivate both more than 6 logs (×1/1,000,000) of Staphylococcus aureus (ATCC 6538) and Escherichia coli (ATCC 8099) within 30 and 10 min, respectively. Moreover, the relatively low blood clotting index of CS/EVC/MC and the activation of platelets adhering to the surfaces indicated that the CS/EVC/MC sample is potential to promote the agglutination abilities of blood cells and simultaneously control wound bleeding. In addition, in vitro cytotoxicity test showed that the CS/EVC/MC had no cytotoxicity. The material might thus have a great potential for biomedical applications.

Decontamination interventions for the reuse of surgical mask personal protective equipment: a systematic review

BACKGROUND

The high demand for personal protective equipment during the novel coronavirus outbreak has prompted the need to develop strategies to conserve supply. Little is known regarding decontamination interventions to allow for surgical mask reuse.

AIM

To identify and synthesize data from original research evaluating interventions to decontaminate surgical masks for the purpose of reuse.

METHODS

MEDLINE, Embase, CENTRAL, Global Health, the WHO COVID-19 database, Google Scholar, DisasterLit, preprint servers, and prominent journals from inception to April 8^th, 2020, were searched for prospective original research on decontamination interventions for surgical masks. Citation screening was conducted independently in duplicate. Study characteristics, interventions, and outcomes were extracted from included studies by two independent reviewers. Outcomes of interest included impact of decontamination interventions on surgical mask performance and germicidal effects.

FINDINGS

Seven studies met eligibility criteria: one evaluated the effects of heat and chemical interventions applied after mask use on mask performance, and six evaluated interventions applied prior to mask use to enhance antimicrobial properties and/or mask performance. Mask performance and germicidal effects were evaluated with heterogeneous test conditions. Safety outcomes were infrequently evaluated. Mask performance was best preserved with dry heat decontamination. Good germicidal effects were observed in salt-, N-halamine-, and nanoparticle-coated masks.

CONCLUSION

There is limited evidence on the safety or efficacy of surgical mask decontamination. Given the heterogeneous methods used in studies to date, we are unable to draw conclusions on the most efficacious and safe intervention for decontaminating surgical masks.

Decontamination interventions for the reuse of surgical mask personal protective equipment: a systematic review

BACKGROUND

The high demand for personal protective equipment during the novel coronavirus outbreak has prompted the need to develop strategies to conserve supply. Little is known regarding decontamination interventions to allow for surgical mask reuse.

AIM

To identify and synthesize data from original research evaluating interventions to decontaminate surgical masks for the purpose of reuse.

METHODS

MEDLINE, Embase, CENTRAL, Global Health, the WHO COVID-19 database, Google Scholar, DisasterLit, preprint servers, and prominent journals from inception to April 8^th, 2020, were searched for prospective original research on decontamination interventions for surgical masks. Citation screening was conducted independently in duplicate. Study characteristics, interventions, and outcomes were extracted from included studies by two independent reviewers. Outcomes of interest included impact of decontamination interventions on surgical mask performance and germicidal effects.

FINDINGS

Seven studies met eligibility criteria: one evaluated the effects of heat and chemical interventions applied after mask use on mask performance, and six evaluated interventions applied prior to mask use to enhance antimicrobial properties and/or mask performance. Mask performance and germicidal effects were evaluated with heterogeneous test conditions. Safety outcomes were infrequently evaluated. Mask performance was best preserved with dry heat decontamination. Good germicidal effects were observed in salt-, N-halamine-, and nanoparticle-coated masks.

CONCLUSION

There is limited evidence on the safety or efficacy of surgical mask decontamination. Given the heterogeneous methods used in studies to date, we are unable to draw conclusions on the most efficacious and safe intervention for decontaminating surgical masks.

Determination of Air Filter Anti-Viral Efficiency against an Airborne Infectious Virus

Recently, various studies have reported the prevention and treatment of respiratory infection outbreaks caused by lethal viruses. Consequently, a variety of air filters coated with antimicrobial agents have been developed to capture and inactivate virus particles in continuous airflow conditions. However, since aerosolized infectious viral-testing is inadvisable due to safety concerns, their anti-viral capability has only been tested by inserting the filters into liquid media, where infectious virus particles disperse. In this study a novel method of determining anti-viral performance of an air filter against airborne infectious viruses is presented. Initially, anti-viral air filter tests were conducted. Firstly, by an air-media test, in which the air filter was placed against an aerosolized non-infectious virus. Secondly, by a liquid-media test, in which the filter was inserted into a liquid medium containing a non-infectious virus. Subsequently, a correlation was established by comparing the susceptibility constants obtained between the two medium tests and an association was found for the air medium test with infectious virus. After ensuring the relationship did not depend on the virus species, the correlation was used to derive the results of the air-medium test from the results of the liquid-medium test.

A Review on Surface-Functionalized Cellulosic Nanostructures as Biocompatible Antibacterial Materials

As the most abundant biopolymer on the earth, cellulose has recently gained significant attention in the development of antibacterial biomaterials. Biodegradability, renewability, strong mechanical properties, tunable aspect ratio, and low density offer tremendous possibilities for the use of cellulose in various fields. Owing to the high number of reactive groups (i.e., hydroxyl groups) on the cellulose surface, it can be readily functionalized with various functional groups, such as aldehydes, carboxylic acids, and amines, leading to diverse properties. In addition, the ease of surface modification of cellulose expands the range of compounds which can be grafted onto its structure, such as proteins, polymers, metal nanoparticles, and antibiotics. There are many studies in which cellulose nano-/microfibrils and nanocrystals are used as a support for antibacterial agents. However, little is known about the relationship between cellulose chemical surface modification and its antibacterial activity or biocompatibility. In this study, we have summarized various techniques for surface modifications of cellulose nanostructures and its derivatives along with their antibacterial and biocompatibility behavior to develop non-leaching and durable antibacterial materials. Despite the high effectiveness of surface-modified cellulosic antibacterial materials, more studies on their mechanism of action, the relationship between their properties and their effectivity, and more in vivo studies are required.

Porous antimicrobial starch particles containing N-halamine functional groups

The porous antimicrobial starch particles containing N-Halamine functional groups (PST-MBA-Cl particles) were synthesized by a crosslinking polymerization between starch (ST) and N, N'-methylenebisacrylamide (MBA), and then a chlorination of amide groups of MBA. The synthetic process used only water as the solvent and was environmentally friendly. The results showed that under the optimal preparation conditions, the as-synthesized PST-MBA-Cl particles could have a Cl⁺% of 8.60 %. Antimicrobial tests showed that PST-MBA-Cl particles had very powerful antimicrobial efficacy against both Staphylococcus aureus and Escherichia coli and could completely kill Staphylococcus aureus with a concentration of 2.1 × 10⁶ CFU/mL and Escherichia coli with a concentration of 5.6 × 10⁶ CFU/mL within a contact time of one minute. Furthermore, the N-Halamine functional groups of PST-MBA-Cl particles also showed excellent stability under storage and reproducibility. Therefore, the as-synthesized PST-MBA-Cl particles will have potential applications in water disinfection.

Fabrication of Polypropylene-g-(Diallylamino Triazine) Bifunctional Nonwovens with Antibacterial and Air Filtration Activities by Reactive Extrusion and Melt-Blown Technology

Air filtration materials such as protective masks can protect humans from airborne pathogens; however, most of the existing protective filtration materials are aimed to intercept bacteria. Therefore, in this work, modified polypropylene- (PP-) based melt-blown nonwovens with antibacterial property were prepared for reducing the infection rate during the filtering process. Firstly, an N-halamine precursor, 2,4-diamino-6-diallylamino-1,3,5-triazine (NDAM) monomer, was grafted with PP polymers (PP-g-NDAM) by reactive extrusion method, and the grafting effect was confirmed by nitrogen analysis and FTIR spectra. Then, the obtained PP-g-NDAM was mixed with pristine PP resins in different ratios to prepare the filter materials by melt-blown technology. Finally, the new PP-g-NDAM melt-blown filter materials were finishing treated by the chlorination and electrostatic process, which showed a high filtration efficiency with low pressure drop and a potent antibacterial effect against Escherichia coli (E. coli). This work provides an innovative method for manufacturing antibacterial filtration nonwovens, which can improve the quality of conventional filtration products.

Bacteria accumulate copper ions and inhibit oxide formation on copper surface during antibacterial efficiency test

Copper surface after antibacterial test against E. coli was examined in the aspect of corrosion. Results from scanning electron microscope (SEM), grazing incidence X-ray diffractometer (GIXRD) and Raman spectroscopy together confirmed less oxidation on copper surface with the presence of E. coli. The inhibition of the cuprous oxide (Cu₂O) layer instead ensured the continuous exposure of copper surface, letting localised corrosion attacks observable and causing a stronger release of copper ions. These phenomena are attributed to the fact that E. coli act as ions reservoirs since high amount of copper accumulation were found by energy dispersive X-ray spectroscopy (EDS).

Antimicrobial and antifouling polymeric coating mitigates persistence of Pseudomonas aeruginosa biofilm

Food wasted due to food spoilage remains a global challenge to the environmental sustainability and security of food supply. In food manufacturing, post-processing contamination of food can occur due to persistent bacterial biofilms, which can be resistant to conventional cleaning and sanitization. The objective was to characterize the efficacy of a polymeric coating in reducing Pseudomonas aeruginosa biofilm establishment and facilitating its removal. Viable cell density of a 48 h biofilm was reduced by 2.10 log cfu cm^-2 on the coated surface, compared to native polypropylene. Confocal laser scanning and electron microscopy indicated reductions in mature biofilm viability and thickness on the coated material. The antifouling coating improved cleanability, with ∼2.5 log cfu cm^-2 of viable cells remaining after 105 min cleaning by water at 65 °C, compared to 4.5 log cfu cm^-2 remaining on native polypropylene. Such coatings may reduce the persistence of biofilms in food processing environments, in support of reducing food spoilage and waste.