Reusable Filters Augmented with Heating Microfibers for Antibacterial and Antiviral Sterilization

The Rise of Electroactive Materials in Face Masks for Preventing Virus Infections

Air-transmitted pathogens may cause severe epidemics, posing considerable threats to public health and safety. Wearing a face mask is one of the most effective ways to prevent respiratory virus infection transmission. Especially since the new coronavirus pandemic, electroactive materials have received much attention in antiviral face masks due to their highly efficient antiviral capabilities, flexible structural design, excellent sustainability, and outstanding safety. This review first introduces the mechanism for preventing viral infection or the inactivation of viruses by electroactive materials. Then, the applications of electrostatic-, conductive-, triboelectric-, and microbattery-based materials in face masks are described in detail. Finally, the problems of various electroactive antiviral materials are summarized, and the prospects for their future development directions are discussed. In conclusion, electroactive materials have attracted great attention for antiviral face masks, and this review will provide a reference for materials scientists and engineers in antiviral materials and interfaces.

Copper-thiosemicarbazone complexes conjugated-cellulose fibers: Biodegradable materials with antibacterial capacity

Personal protective equipment (PPE) is vital in battling bacteria crisis, but conventional PPE materials lack antimicrobial activities and environmental friendliness. Our work focused on developing biodegradable and antibacterial fibers as promising bioprotective materials. Here, we grafted highly effective antibacterial copper-thiosemicarbazone complexes (CT1-4) on cellulose fibers via covalent linkages. Multiple methods were used to characterize the chemical composition or morphology of CT1-4 conjugated-fibers. Conjugation of CT1-4 maintains the mechanical properties (Breaking strength: 2.35-2.45 cN/dtex, Breaking elongation: 7.19 %-7.42 %) and thermal stability of fibers. CT1 can endow cellulose fibers with the excellent growth inhibition towards Escherichia coli (E. coli) (GIR: 61.5 % ± 1.28 %), Staphylococcus aureus (S. aureus) (GIR: 85.7 % ± 1.93 %), and Bacillus subtilis (B. subtilis) (GIR: 87.6 % ± 1.44 %). We believe that the application of CT1 conjugated-cellulose fibers is not limited to the high-performance PPE, and also can be extended to various types of protective equipment for food and medicine safety.

Development of Environmentally Friendly Biocidal Coatings Based on Water-soluble Copolymers for Air-cleaning Filters

Air pollution by pathogens has posed serious concern on global health during the last decades, especially since the breakout of the last pandemic. Therefore, advanced high-efficiency techniques for air purification are highly on demand. However, in air-filtering devices, the prevention of secondary pollution that may occur on the filters remains a challenge. Toward this goal, in the present work, we demonstrate a facile and eco-friendly process for the biocidal treatment of commercial high-efficiency particulate air filters. The antibacterial filters were successfully prepared through spray coating of aqueous solutions based on biocidal water-soluble polymers, poly(sodium 4-styrene sulfonate-co-cetyl trimethylammonium 4-styrene sulfonate-co-glycidyl methacrylate) [P(SSNa24-co-SSAmC₁₆56-co-GMA20)] and poly(2-dimethylaminoethyl)methacrylate. Significantly, an optimized green route was developed for the synthesis of the used polymers in aqueous conditions and their stabilization through cross-linking reaction, leading to biocidal air filters with long-lasting activity. The developed coatings presented strong and rapid antibacterial activity against Staphylococcus aureus (in 5 min) and Escherichia coli (in 15 min). Moreover, the cytotoxicity test of the polymeric materials toward Α549 lung adenocarcinoma cells indicated very low toxicity as they did not affect either the cell growth or cell morphology. The above-mentioned results together with the scalable and easy-to-produce green methodology suggest that these materials can be promising candidates as filter coatings for use on air-purification devices.

Carbonized lotus leaf/ZnO/Au for enhanced synergistic mechanical and photocatalytic bactericidal activity under visible light irradiation

Nowadays, bacterial resistance has continued to be a troublesome issue caused by the abuse of antibiotics, and it is the paramount difficulty in resolving the bacterial proliferation and infection. In this study, fresh lotus leaf was treated with Zn²⁺ followed by sintered and modification with gold nanoparticles through the photoreduction process sequentially, and thus a composite of micro/nanostructured carbonized lotus leaf/ZnO/Au (C-LL/ZnO/Au) was obtained to explore its bactericidal properties. C-LL/ZnO/Au retained the papillary structure of fresh lotus leaf and showed great mechanical bactericidal performance and photocatalytic sterilization. The antibacterial rate of mechanical sterilization for C-LL/ZnO/Au amount to 79.5% in 30 min, 4.7 times of fresh lotus leaf's figure under the same conditions. Furthermore, in C-LL/ZnO/Au, the introduction of gold nanoparticles heightened light absorbance through localized surface plasmon resonance (LSPR) effect and separation efficiency of photogenerated electron-hole pairs, which showed improved photocatalytic sterilization than that of carbonized lotus leaf/ZnO (C-LL/ZnO). Carbonized lotus leaf/ZnO/Au exhibited prominent photocatalytic and mechanical synergistic antibacterial performance against E. coli: all the bacteria were inactivated within 30 min under visible light. The approach presented here could be applied to a variety of biomass materials, which holds a promising application potential in biomedical, public health and other fields.

Nanostructures for the Prevention, Diagnosis, and Treatment of SARS-CoV-2: A Review

Scientists, doctors, engineers, and even entire societies have become aware of the seriousness of the COVID-19 infection and are taking action quickly, using all the tools from protection to treatment against coronavirus SARS-CoV-2. Especially in this sense, scientific approaches and materials using nanotechnology are frequently preferred. In this review, we focus on how nanoscience and nanotechnology approaches can be used for protective equipment, diagnostic and treatment methods, medicine, and vaccine applications to stop the coronavirus SARS-CoV-2 and prevent its spread. SARS-CoV-2, which itself can be considered as a core-shell nanoparticle, can interact with various materials around it and remain bound for variable periods of time while maintaining its bioactivity. These applications are especially critical for the controlled use of disinfection systems. One of the most important processes in the fight against coronavirus is the rapid diagnosis of the virus in humans and the initiation of isolation and treatment processes. The development of nanotechnology-based test and diagnostic kits is another important research thrust. Nanotechnological therapeutics based on antiviral drug design and nanoarchitecture vaccines have been vital. Nanotechnology plays critical roles in the production of protective film surfaces for self-cleaning and antiviral masks, gloves, and laboratory clothes. An overview of literature studies highlighting nanotechnology and nanomaterial-based approaches to combat SARS-CoV-2 is presented.

Fabrication of air filters with advanced filtration performance for removal of viral aerosols and control the spread of COVID-19

COVID-19 is caused via the SARS-CoV-2 virus, a lipid-based enveloped virus with spike-like projections. At present, the global epidemic of COVID-19 continues and waves of SARS-CoV-2, the mutant Delta and Omicron variant which are associated with enhanced transmissibility and evasion to vaccine-induced immunity have increased hospitalization and mortality, the biggest challenge we face is whether we will be able to overcome this virus? On the other side, warm seasons and heat have increased the need for proper ventilation systems to trap contaminants containing the virus. Besides, heat and sweating accelerate the growth of microorganisms. For example, medical staff that is in the front line use masks for a long time, and their facial sweat causes microbes to grow on the mask. Nowadays, efficient air filters with anti-viral and antimicrobial properties have received a lot of attention, and are used to make ventilation systems or medical masks. A wide range of materials plays an important role in the production of efficient air filters. For example, metals, metal oxides, or antimicrobial metal species that have anti-viral and antimicrobial properties, including Ag, ZnO, TiO₂, CuO, and Cu played a role in this regard. Carbon nanomaterials such as carbon nanotubes, graphene, or derivatives have also shown their role well. In addition, natural materials such as biopolymers such as alginate, and herbal extracts are employed to prepare effective air filters. In this review, we summarized the utilization of diverse materials in the preparation of efficient air filters to apply in the preparation of medical masks and ventilation systems. In the first part, the employing metal and metal oxides is examined, and the second part summarizes the application of carbon materials for the fabrication of air filters. After examination of the performance of natural materials, challenges and progress visions are discussed.

Advances in particulate matter filtration: Materials, performance, and application

Air-borne pollutants in particulate matter (PM) form, produced either physically during industrial processes or certain biological routes, have posed a great threat to human health. Particularly during the current COVID-19 pandemic, effective filtration of the virus is an urgent matter worldwide. In this review, we first introduce some fundamentals about PM, including its source and classification, filtration mechanisms, and evaluation parameters. Advanced filtration materials and their functions are then summarized, among which polymers and MOFs are discussed in detail together with their antibacterial performance. The discussion on the application is divided into end-of-pipe treatment and source control. Finally, we conclude this review with our prospective view on future research in this area.

Antiviral/antibacterial biodegradable cellulose nonwovens as environmentally friendly and bioprotective materials with potential to minimize microplastic pollution

Personal protective equipment (PPE) such as face masks is vital in battling the COVID-19 crisis, but the dominant polypropylene-based PPE are lack of antiviral/antibacterial activities and environmental friendliness, and have hazardous impact on the soil and aquatic ecosystems. The work presented herein focused on developing biodegradable, antiviral, and antibacterial cellulose nonwovens (AVAB-CNWs) as a multi-functional bioprotective layer for better protection against coronavirus SARS-CoV-2 and addressing environmental concerns raised by the piling of COVID-19 related wastes. Both guanidine-based polymer and neomycin sulfate (NEO) were reactive-modified and covalently grafted onto the surface of cellulose nonwovens, thereby conferring outstanding antiviral and antibacterial activities to the nonwovens without deteriorating the microstructure and biodegradability. Through adjusting the grafting amount of active components and selecting appropriate reagents for pretreatment, the antimicrobial activity and hydrophobicity for self-cleaning of the nonwovens can be tuned. More importantly, we demonstrated for the first time that such multi-functional nonwovens are capable of inactivating SARS-CoV-2 instantly, leading to high virucidal activity (> 99.35%), which is unachievable by conventional masks used nowadays. Meanwhile, the robust breathability and biodegradability of AVAB-CNWs were well maintained. The applications of the as-prepared nonwovens as high-performance textile can be readily extended to other areas in the fight against COVID-19.

Synthesis of polyacrylonitrile/polytetrahydropyrimidine (PAN/PTHP) nanofibers with enhanced antibacterial and anti-viral activities for personal protective equipment

Emerging infectious diseases caused by the spread of bacteria and viruses are a major burden on global economic development and public health. At present, most personal protective equipment has weak antibacterial and anti-viral properties. The PAN/PTHP nanofibers reported in this article provide a new method for the development of personal protective equipment. In this study, a mixture of PTHP and PAN was prepared into PAN/PTHP nanofibers with high-efficiency and long-lasting antibacterial effects (>99.999%) through the electrospinning process. Live/dead staining and cell proliferation experiments showed that the preparation of PAN/PTHP nanofibers has good cell compatibility. In addition, PAN/PTHP nanofibers show obvious destructive effects on lentiviruses. Based on these characteristics, PAN/PTHP nanofibers were applied to facial masks, which can be used as the inflatable biocidal layer of facial masks and have an excellent interception effect on particles in the air. The successful synthesis of these fascinating materials may provide new insights for the development of new protective materials.

Electrospun membranes filtering 100 nm particles from air flow by means of the van der Waals and Coulomb forces

Nonwoven fibrous filter membranes are widely used in filtration because of their low cost. They are less effective in intercepting airborne particles of the order of 100 nm, which is of the SARS-CoV-2 (COVID-19) virus's size. Many diseases, including COVID-19, predominantly spread by droplets released by breathing, coughing, sneezing, or medical procedures. It was shown that the smallest droplets can evaporate in air before settling, thus, making viruses airborne and easily penetrating even the best masks and filters. As a result, air-filtering membranes, which are capable of effective interception of ∼100 nm nanoparticles are highly desirable. A traditional way to improve filtration efficiency by overlapping several layers of nonwoven fabrics increases the required pressure drop, and thus, should be avoided as much as possible. Here, we propose and demonstrate an innovative approach to enhance performance of filtration membranes based on (i) a dramatic reduction in the fiber size, and (ii) metal coating of the fibers. The first component of this approach allows one to incorporate a novel physical mechanism of filtration, the short-range van der Waals forces, whereas the second one adds the long-range electric Coulomb forces if the oncoming nanoparticles are pre-charged and the metal-plated membrane grounded. In the present work, the ∼100 nm aluminum nanoparticles are filtered as a model of commensurate airborne single COVID-19 viruses, and Platinum is used as the sputter-coated material for the fiber coating. The resulting filtration efficiency enhanced by the electric Coulomb forces alone is increased by the factor of 1.77, while the filtration efficiency additionally facilitated by the van der Waals forces increased by the factor of 2.44. In comparison to the filter membranes with ∼500 nm fibers without the electric forces involved, the van-der-Waals-electric filter membrane with fibers ∼90 nm is 2.24 × 1.77 = 3.96 times more effective. The quality factor of a membrane which combines the van der Waals and Coulomb forces is 10.6 psi^-1, which is almost three times that of a comparable membrane without the electric Coulomb force (with only van der Waals forces being used).

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.

Virucidal and biodegradable specialty cellulose nonwovens as personal protective equipment against COVID-19 pandemic

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Enable to instantly inactivate SARS-CoV-2 (>99.14%) and HCoV-229E (>98.83%).

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Excellent growth inhibition (>99.51%) towards both E. coli and S. aureus.

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Address the environmental concerns raised by non-biodegradable face masks.

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Development of safe, comfortable, and biodegradable textiles for PPE.

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A facile and scalable method to produce biocidal textiles for various applications.

Introduction

Face masks are regarded as effective Personal Protective Equipment (PPE) during the COVID-19 pandemic. However, the dominant polypropylene (PP)-based masks are devoid of antiviral/antibacterial activities and create enormous environmental burdens after disposal.

Objectives

Here we report a facile and potentially scalable method to fabricate biodegradable, breathable, and biocidal cellulose nonwovens (BCNWs) to address both environmental and hygienic problems of commercially available face masks.

Methods

TEMPO-oxidized cellulose nonwovens are rendered antiviral/antibacterial via covalent bonding with disinfecting polyhexamethylene guanidine or neomycin sulfate through carbodiimide coupling chemistry.

Results

The obtained results showed that the BCNWs have virucidal rate of >99.14%, bactericidal efficiency of >99.51%, no leaching-out effect, and excellent air permeability of >1111.5 mm s⁻¹. More importantly, the as-prepared BCNWs can inactivate SARS-CoV-2 instantly.

Conclusions

This strategy provides a new platform for the green fabrication of multifunctional cellulose nonwovens as scalable bio-protective layers with superior performance for various PPE in fighting COVID-19 or future pandemics. Additionally, replacing the non-biodegradable non-antimicrobial PP-based masks with the cellulose-based masks can reduce the plastic wastes and lower the greenhouse gas production from the incineration of disposed masks.

Functionalized Masks: Powerful Materials against COVID-19 and Future Pandemics

The outbreak of COVID-19 revealed the vulnerability of commercially available face masks. Without having antibacterial/antiviral activities, the current masks act only as filtering materials of the aerosols containing microorganisms. Meanwhile, in surgical masks, the viral and bacterial filtration highly depends on the electrostatic charges of masks. These electrostatic charges disappear after 8 h, which leads to a significant decline in filtration efficiency. Therefore, to enhance the masks' protection performance, fabrication of innovative masks with more advanced functions is in urgent demand. This review summarizes the various functionalizing agents which can endow four important functions in the masks including i) boosting the antimicrobial and self-disinfectant characteristics via incorporating metal nanoparticles or photosensitizers, ii) increasing the self-cleaning by inserting superhydrophobic materials such as graphenes and alkyl silanes, iii) creating photo/electrothermal properties by forming graphene and metal thin films within the masks, and iv) incorporating triboelectric nanogenerators among the friction layers of masks to stabilize the electrostatic charges and facilitating the recharging of masks. The strategies for creating these properties toward the functionalized masks are discussed in detail. The effectiveness and limitation of each method in generating the desired properties are well-explained along with addressing the prospects for the future development of masks.