A laboratory-based study examining the properties of silk fabric to evaluate its potential as a protective barrier for personal protective equipment and as a functional material for face coverings during the COVID-19 pandemic

Assessment and design of filters and masks against COVID-19 via modeling and simulations

This study aimed to evaluate and design masks against viruses, especially SARS-CoV-2 associated with COVID-19. A continuum filtration model was developed where the rate of particle deposition and "sticking" on the filter fibers is a critical term in the mass transfer, together with permeation velocity, filter porosity, tortuosity, and Brownian diffusion. CFD simulations of the airflow during respiration lead to the recommendation that the filter permeability should be above 4 × 10-11 m2 to direct the airflow for effectiveness against virus particles; otherwise, low filter permeabilities cause the unfiltered air to flow preferentially through the leak gaps between the mask and the headform. Different mask filters with microstructural and geometry data from the literature are assessed via filtration simulations for breathability and filtration efficiency. The results demonstrate that a surgical mask of 25% porosity, pore size of 150 µm and permeability of 4.4 × 10-11 m2 can achieve 100% minimum efficiency while demonstrating high breathability, complying with the criteria of FFP3, N95, and surgical Class II and IIR masks. Selected cotton and synthetic cloths as well as electrospun fiber layers are predicted to comply with FFP2, N95, and surgical mask Class II and IIR standards.

Mechanical Properties of Twisted Cellulose Nanofiber-Reinforced Silk Yarns

Silk has recently attracted considerable interest owing to its versatile properties as a natural fiber, especially in the medical sector. However, the mechanical properties of silk limit its potential applications. In our earlier work, the mechanical performance of silk filaments was enhanced owing to the insertion of cellulose nanofibers (CNFs). Nevertheless, silk filaments must be assembled and twisted to form a continuous yarn. In this study, the mechanical properties of CNF-reinforced silk yarns were evaluated to determine the optimal yarn structure. The evolution of the Young's modulus, ultimate tensile strength, toughness, and elongation at break was assessed as a function of the twist level in comparison with regular silk. The results demonstrated that the most favorable compromise of the mechanical properties was obtained at 1000 twists per meter.

Selenium-silk microgels as antifungal and antibacterial agents

Antimicrobial resistance is a leading threat to global health. Alternative therapeutics to combat the rise in drug-resistant strains of bacteria and fungi are thus needed, but the development of new classes of small molecule therapeutics has remained challenging. Here, we explore an orthogonal approach and address this issue by synthesising micro-scale, protein colloidal particles that possess potent antimicrobial properties. We describe an approach for forming silk-based microgels that contain selenium nanoparticles embedded within the protein scaffold. We demonstrate that these materials have both antibacterial and antifungal properties while, crucially, also remaining highly biocompatible with mammalian cell lines. By combing the nanoparticles with silk, the protein microgel is able to fulfill two critical functions; it protects the mammalian cells from the cytotoxic effects of the bare nanoparticles, while simultaneously serving as a carrier for microbial eradication. Furthermore, since the antimicrobial activity originates from physical contact, bacteria and fungi are unlikely to develop resistance to our hybrid biomaterials, which remains a critical issue with current antibiotic and antifungal treatments. Therefore, taken together, these results provide the basis for innovative antimicrobial materials that can target drug-resistant microbial infections.

Functional Textile Materials for Blocking COVID-19 Transmission

The outbreak of COVID-19 provided a warning sign for society worldwide: that is, we urgently need to explore effective strategies for combating unpredictable viral pandemics. Protective textiles such as surgery masks have played an important role in the mitigation of the COVID-19 pandemic, while revealing serious challenges in terms of supply, cross-infection risk, and environmental pollution. In this context, textiles with an antivirus functionality have attracted increasing attention, and many innovative proposals with exciting commercial possibilities have been reported over the past three years. In this review, we illustrate the progress of textile filtration for pandemics and summarize the recent development of antiviral textiles for personal protective purposes by cataloging them into three classes: metal-based, carbon-based, and polymer-based materials. We focused on the preparation routes of emerging antiviral textiles, providing a forward-looking perspective on their opportunities and challenges, to evaluate their efficacy, scale up their manufacturing processes, and expand their high-volume applications. Based on this review, we conclude that ideal antiviral textiles are characterized by a high filtration efficiency, reliable antiviral effect, long storage life, and recyclability. The expected manufacturing processes should be economically feasible, scalable, and quickly responsive.

Eco-friendly acid dyeing of silk and wool fabrics using Acid Violet 49 dye

The effluent load from textile industries has forced traders and industrialists to use sustainable tools that not only save energy, money, and labor but also make the process cleaner. The purpose of this study is to improve the dyeing of proteinous fabrics using Acid Violet 49 dye under microwave radiation. Aqueous and acidic dye solutions were prepared and treated with MW radiations for up to 10 min. MW treated and untreated dye solutions were used to color treated and untreated fabrics to observe color yield. It has been found that dyeing of irradiated silk at 65 °C for 35 min, using 55 mL of irradiated dye solution containing 1 g/100 mL salt, has given excellent results. Whereas good color characteristics are obtained if irradiated wool fabric is dyed at 85 °C for 55 min, using 55 mL irradiated dye solution using 1 g/100 mL salt. Physicochemical analysis reveals that MW rays have physically modified the fabric without altering its chemistry. ISO standard methods employed for colorfastness show that under optimal conditions, the color developed is fast; statistical analysis shows that the dyeing process has given significant results. It is concluded that MW rays have excellent potential to improve acidic dyeing of proteinous fabric under mild conditions which show that the utilization of MW rays is a cost-, time-, and energy-effective process.

Materials analysis and image-based modelling of transmissibility and strain behaviour in approved face mask microstructures

Comparisons are made between six different approved face masks concerning their particle transmissibility allied to mechanical properties. The latter involves material testing and stretch or strain behaviour under load. SEM and X-ray elemental analyses showed contrasting structures between random and ordered fibre orientations. These constitute the mask designs where transmissibility is to be minimised. Airflow velocity measurement enabled filtration to be measured between the different mask designs, from two to six layers of different fabrics in combination. SEM provided the fibre diameter and pore size of each mask layer, up to a maximum of six. Stretching each complete mask showed its elasticity and recovery behaviour on an energy basis. The energy conversion involved in mask straining involves areas enclosed within steady and cyclic load-extension plots. Thus, the work done in extending a mask and the energy recovered from its release identified a hysteresis associated with an irrecoverable permanent stretch to the mask fabric. Failure of individual layers, which occurred successively in extended stretch tests, appeared as a drop in a load-extension response. That change is associated with permanent damage to each mask and friction contact within the rearrangement of loose fibre weaves. Masks with the greatest number of layers reduced particle transmissibility. However, woven or ordered mask fabrics in two layers with different orientations provided comparable performance. Simulation of each mechanical response, velocity streamlining and fibre distribution within the mask layers are also presented.

Rapid Method to Quantify the Antiviral Potential of Porous and Nonporous Material Using the Enveloped Bacteriophage Phi6

The pandemic revealed significant gaps in our understanding of the antiviral potential of porous textiles used for personal protective equipment and nonporous touch surfaces. What is the fate of a microbe when it encounters an abiotic surface? How can we change the microenvironment of materials to improve antimicrobial properties? Filling these gaps requires increasing data generation throughput. A method to accomplish this leverages the use of the enveloped bacteriophage ϕ6, an adjustable spacing multichannel pipette, and the statistical design opportunities inherent in the ordered array of the 24-well culture plate format, resulting in a semi-automated small drop assay. For 100 mm² nonporous coupons of Cu and Zn, the reduction in ϕ6 infectivity fits first-order kinetics, resulting in half-lives (T₅₀) of 4.2 ± 0.1 and 29.4 ± 1.6 min, respectively. In contrast, exposure to stainless steel has no significant effect on infectivity. For porous textiles, differences associated with composition, color, and surface treatment of samples are detected within 5 min of exposure. Half-lives for differently dyed Zn-containing fabrics from commercially available masks ranged from 2.1 ± 0.05 to 9.4 ± 0.2 min. A path toward full automation and the application of machine learning techniques to guide combinatorial material engineering is presented.

Evaluation of the Microbiological Effectiveness of Three Accessible Mask Decontamination Methods and Their Impact on Filtration, Air Permeability and Physicochemical Properties

The need to secure public health and mitigate the environmental impact associated with the massified use of respiratory protective devices (RPD) has been raising awareness for the safe reuse of decontaminated masks by individuals and organizations. Among the decontamination treatments proposed, in this work, three methods with the potential to be adopted by households and organizations of different sizes were analysed: contact with nebulized hydrogen peroxide (H2O2); immersion in commercial bleach (NaClO) (sodium hypochlorite, 0.1% p/v); and contact with steam in microwave steam-sanitizing bags (steam bag). Their decontamination effectiveness was assessed using reference microorganisms following international standards (issued by ISO and FDA). Furthermore, the impact on filtration efficiency, air permeability and several physicochemical and structural characteristics of the masks, were evaluated for untreated masks and after 1, 5 and 10 cycles of treatment. Three types of RPD were analysed: surgical, KN95, and cloth masks. Results demonstrated that the H2O2 protocol sterilized KN95 and surgical masks (reduction of >6 log10 CFUs) and disinfected cloth masks (reduction of >3 log10 CFUs). The NaClO protocol sterilized surgical masks, and disinfected KN95 and cloth masks. Steam bags sterilized KN95 and disinfected surgical and cloth masks. No relevant impact was observed on filtration efficiency.

ALD based nanostructured zinc oxide coated antiviral silk fabric

The COVID-19 pandemic has underscored the importance of research and development in maintaining public health. Facing unprecedented challenges, the scientific community developed antiviral drugs, virucides, and vaccines to combat the infection within the past two years. However, an ever-increasing list of highly infectious SARS-CoV-2 variants (gamma, delta, omicron, and now ba.2 stealth) has exacerbated the problem: again raising the issues of infection prevention strategies and the efficacy of personal protective equipment (PPE). Against this backdrop, we report an antimicrobial fabric for PPE applications. We have fabricated a nanofibrous silk-PEO material using electrospinning followed by zinc oxide thin film deposition by employing the atomic layer deposition technique. The composite fabric has shown 85% more antibacterial activity than the control fabric and was found to possess substantial superoxide dismutase–mimetic activity. The composite was further subjected to antiviral testing using two different respiratory tract viruses: coronavirus (OC43: enveloped) and rhinovirus (RV14: non-enveloped). We report a 95% reduction in infectious virus for both OC43 and RV14 from an initial load of ∼1 × 10⁵ (sample size: 6 mm dia. disk), after 1 h of white light illumination. Furthermore, with 2 h of illumination, ∼99% reduction in viral infectivity was observed for RV14. High activity in a relatively small area of fabric (3.5 × 10³ viral units per mm²) makes this antiviral fabric ideal for application in masks/PPE, with an enhanced ability to prevent antimicrobial infection overall.

This study presents an antiviral self-cleaning fabric for masks/PPE applications with protection against human coronavirus.

Masks for COVID-19

Sustainable solutions on fabricating and using a face mask to block the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spread during this coronavirus pandemic of 2019 (COVID-19) are required as society is directed by the World Health Organization (WHO) toward wearing it, resulting in an increasingly huge demand with over 4 000 000 000 masks used per day globally. Herein, various new mask technologies and advanced materials are reviewed to deal with critical shortages, cross-infection, and secondary transmission risk of masks. A number of countries have used cloth masks and 3D-printed masks as substitutes, whose filtration efficiencies can be improved by using nanofibers or mixing other polymers into them. Since 2020, researchers continue to improve the performance of masks by adding various functionalities, for example using metal nanoparticles and herbal extracts to inactivate pathogens, using graphene to make masks photothermal and superhydrophobic, and using triboelectric nanogenerator (TENG) to prolong mask lifetime. The recent advances in material technology have led to the development of antimicrobial coatings, which are introduced in this review. When incorporated into masks, these advanced materials and technologies can aid in the prevention of secondary transmission of the virus.

COVID-19 Pandemic: Public Health Risk Assessment and Risk Mitigation Strategies

A newly emerged respiratory viral disease called severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is also known as pandemic coronavirus disease (COVID-19). This pandemic has resulted an unprecedented global health crisis and devastating impact on several sectors of human lives and economies. Fortunately, the average case fatality ratio for SARS-CoV-2 is below 2%, much lower than that estimated for MERS (34%) and SARS (11%). However, COVID-19 has a much higher transmissibility rate, as evident from the constant increase in the count of infections worldwide. This article explores the reasons behind how COVID-19 was able to cause a global pandemic crisis. The current outbreak scenario and causes of rapid global spread are examined using recent developments in the literature, epidemiological features relevant to public health awareness, and critical perspective of risk assessment and mitigation strategies. Effective pandemic risk mitigation measures have been established and amended against COVID-19 diseases, but there is still much scope for upgrading execution and coordination among authorities in terms of organizational leadership's commitment and diverse range of safety measures, including administrative control measures, engineering control measures, and personal protective equipment (PPE). The significance of containment interventions against the COVID-19 pandemic is now well established; however, there is a need for its effective execution across the globe, and for the improvement of the performance of risk mitigation practices and suppression of future pandemic crises.

Nanometer-Thick Superhydrophobic Coating Renders Cloth Mask Potentially Effective against Aerosol-Driven Infections

The advent of COVID-19 pandemic has made it necessary to wear masks across populations. While the N95 mask offers great performance against airborne infections, its multilayered sealed design makes it difficult to breathe for a longer duration of use. The option of using highly breathable cloth or silk masks especially for a large populace is fraught with the danger of infection. As a normal cloth or silk mask absorbs airborne liquid, it can be a source of plausible infection. We demonstrate the chemical modification of one such mask, Eri silk, to make it hydrophobic (contact angle of water is 143.7°), which reduces the liquid absorption capacity without reducing the breathability of the mask significantly. The breathability reduces only 22% for hydrophobic Eri silk compared to the pristine Eri silk, whereas N95 shows a 59% reduction of breathability. The modified hydrophobic silk can repel the incoming aqueous liquid droplets without wetting the surface. The results indicate that a multilayered modified silk mask to make it hydrophobic can be an affordable and breathable alternative to the N95 mask.

Functionalized poly(lactic acid) based nano-fabric for anti-viral applications

This study endeavoured to explore and fabricate antiviral and antibacterial facemasks using zinc (oligo-lactate) (ZL), developed through a microwave synthesis technique. The prepared nano-fabric layer has excellent antiviral and antibacterial properties against Newcastle Disease Virus (NDV) and E. coli and S. aureus, respectively. Thermogravimetric analysis (TGA) of ZL shows a two-step thermal degradation, which confirms the formation of low molecular weight end group lactyl units with zinc ions. Another investigation using varying ZL concentration and silk nanocrystal (SNC) with poly(lactic acid) (PLA) and electrospinning them into nanofibres led to the fabrication of a facile and sustainable nanofabric that can be utilized as a protective layer for facemasks. Morphological analysis revealed the successful preparation of the nanofabric with proper distribution and uniformity in fibre diameter. Hydrophobicity of the prepared nanofabric confirmed excellent protection from water droplets that may transpire during coughing or sneezing by an infected individual. Breathability and reusability tests confirmed that the prepared facemask could be reused by ethanol washing without compromising its surface properties till 4 cycles. The PLA/ZL nanofabric layer demonstrated 97% antiviral efficacy against NDV in 10 minutes. In conclusion, the electrospun nanofabric layer can be used as a facemask having high hydrophobicity, good breathability, antibacterial, and antiviral properties to control the spread of contagious diseases.

Dimorphic cocoons of the robin moth, Hyalophora cecropia, reflect the existence of two distinct architectural syndromes

The architectural design of animal structures forms part of an individual's extended phenotype that can be subjected to strong selection pressures. We examined cocoon architectural dimorphism in robin moths (Hyalophora cecropia), which construct multilayered silk-woven cocoons that possess either a 'baggy' or 'compact' morphology. These dimorphic cocoons reflect extended phenotypes that can enable survival during a critical developmental period (pupal stage to adult emergence), with cocoons occurring either sympatrically or as monomorphic groups across different climatic regions in North America. We hypothesized that cocoon dimorphism is related to the cocoon's role as a mediating barrier for moisture. We predicted that the macro- and micro-architectural differences between the cocoon morphs would be consistent with this function. We compared the cocoon morphs in terms of their orientation when spun under natural field conditions, examined how these orientations affected cocoon water absorption under simulated rain trials, and performed material surface tests to compare the hydrophobicity of cocoons. We found that compact cocoons had traits that increased water resistance, as they had significantly greater hydrophobicity than baggy cocoons, because they absorbed less water and released water vapor faster. In contrast, the increased water absorptiveness of baggy cocoons can allow for greater moisture retention, a function related to the prevention of desiccation. Our study suggests that cocoon dimorphism in robin moths reflects distinct architectural syndromes, in which cocoons are spun to optimize either water resistance or retention. These different functions are consistent with strategies that act to respond to uncertain external environmental conditions that an individual might encounter during development.

Historical Evolution and Filtering Characteristics of Masks and Respirators in Dentistry in the Context of COVID-19: A Literature Review

OBJECTIVES

At present, it is very important to identify the available literature regarding the use of masks and respirators by analyzing their historical evolution in the medical field. In addition, consideration should be given to the major filtering characteristics of those most used due to the current SARS-CoV-2 pandemic. Therefore, the purpose of this literature review is to describe the qualitative evolution that facemasks and respirators have undergone along with their different characteristics.

MATERIALS AND METHODS

This literature review was conducted between September and December 2020. Articles were identified from PubMed Central, Scopus, and Web of Science. The following keywords were used: "COVID-19," "dentistry," and "masks." These MeSH terms were combined with the Boolean operators "AND" and "OR."

RESULTS

We found 36 articles in PubMed Central, 21 in Scopus, and 17 in Web of Science, which included reviews, clinical, descriptive, and experimental trials.

CONCLUSION

The emergence of new pathogens leads to continuous improvement in masks and respirators. It was determined that for the dental field, respirators with filtration characteristics greater than 95%, such as FFP3, N100, N95, and KN95, are indicated in addition to their decontamination and reuse processes.

The effect of N95 and surgical masks on mucociliary clearance function and sinonasal complaints

PURPOSE

The aim of this study was to reveal the effect of N95 and surgical masks on mucociliary clearance function and sinonasal complaints.

METHODS

Sixty participants were enrolled in this study, including 30 people in N95 mask group and 30 people in surgical mask group. Two interviews, three days apart, were performed with all participants. The participants were asked not to use any mask before the first interview while they were asked to use the determined mask just before the second interview for 8 h. In both interviews, the mucociliary clearance times (MCTs) were measured and participants were asked to score ten distinct sinonasal complaints using visual analog scale (VAS). Data obtained from first interview were named pre-mask data, data obtained from second interview were called after-mask data. In both groups, pre-mask MCTs and VAS scores were compared with after-mask MCTs and VAS scores.

RESULTS

After-mask MCTs (mean = 13.03 ± 6.05 min) were significantly longer than pre-mask MCTs (mean = 10.19 ± 4.21 min) in N95 mask group (p = 0.002). No significant difference was found between after-mask and pre-mask MCTs (mean = 12.05 ± 5.21 min, mean = 11.00 ± 5.44 min, respectively) in surgical mask group (p = 0.234). When after-mask VAS scores were compared with pre-mask VAS scores, it was found that N95 mask use increased nasal blockage and postnasal discharge, surgical mask usage increased nasal blockage.

CONCLUSION

While the use of N95 mask leads to nasal blockage and postnasal discharge, surgical mask use results in nasal blockage. N95 masks cause impairment in mucociliary clearance function. But all these effects are mild. Surgical masks have not been found to have any effect on mucociliary clearance function.

Review of the Breathability and Filtration Efficiency of Common Household Materials for Face Masks

The World Health Organization and the United States Centers for Disease Control have recommended universal face masking by the general public to slow the spread of COVID-19. A number of recent studies have evaluated the filtration efficiency and pressure differential (an indicator of breathability) of various, widely available materials that the general public can use to make face masks at home. In this review, we summarize those studies to provide guidance for both the public to select the best materials for face masks and for future researchers to rigorously evaluate and report on mask material testing. Of the tested fabric materials and material combinations with adequate breathability, most single and multilayer combinations had a filtration efficiency of <30%. Most studies evaluating commonly available mask materials did not follow standard methods that would facilitate comparison across studies, and materials were often described with too few details to allow consumers to purchase equivalent materials to make their own masks. To improve the usability of future study results, researchers should use standard methods and report material characteristics in detail.