Boosting Copper Biocidal Activity by Silver Decoration and Few-Layer Graphene in Coatings on Textile Fibers

The outbreak of the Coronavirus disease 2019 (COVID-19) pandemic has highlighted the importance of developing antiviral surface coatings that are capable of repelling pathogens and neutralizing them through self-sanitizing properties. In this study, a novel coating design based on few-layer graphene (FLG) is proposed and silver-decorated micro copper flakes (CuMF) that exhibit both antibacterial and antiviral properties. The role of sacrificial anode surfaces and intrinsic graphene defects in enhancing the release of metal ions from CuMF embedded in water-based binders is investigated. In silico analysis is conducted to better understand the molecular interactions of pathogen-repelling species with bacterial or bacteriophage proteins. The results show that the optimal amount of CuMF/FLG in the coating leads to a significant reduction in bacterial growth, with reductions of 3.17 and 9.81 log for Staphylococcus aureus and Escherichia coli, respectively. The same coating also showed high antiviral efficacy, reducing bacteriophage phi6 by 5.53 log. The antiviral efficiency of the coating is find to be doubled compared to either micro copper flakes or few-layer graphene alone. This novel coating design is versatile and can be applied to various substrates, such as personal protective clothing and face masks, to provide biocidal activity against both bacterial and viral pathogens.

Screen-printing of chitosan and cationised cellulose nanofibril coatings for integration into functional face masks with potential antiviral activity

Masks proved to be necessary protective measure during the COVID-19 pandemic, but they provided a physical barrier rather than inactivating viruses, increasing the risk of cross-infection. In this study, high-molecular weight chitosan and cationised cellulose nanofibrils were screen-printed individually or as a mixture onto the inner surface of the first polypropylene (PP) layer. First, biopolymers were evaluated by various physicochemical methods for their suitability for screen-printing and antiviral activity. Second, the effect of the coatings was evaluated by analysing the morphology, surface chemistry, charge of the modified PP layer, air permeability, water-vapour retention, add-on, contact angle, antiviral activity against the model virus phi6 and cytotoxicity. Finally, the functional PP layers were integrated into face masks, and resulting masks were tested for wettability, air permeability, and viral filtration efficiency (VFE). Air permeability was reduced for modified PP layers (43 % reduction for kat-CNF) and face masks (52 % reduction of kat-CNF layer). The antiviral potential of the modified PP layers against phi6 showed inhibition of 0.08 to 0.97 log (pH 7.5) and cytotoxicity assay showed cell viability above 70 %. VFE of the masks remained the same (~99.9 %), even after applying the biopolymers, confirming that these masks provided high level of protection against viruses.

Assessment of Different Experimental Setups to Determine Viral Filtration Efficiency of Face Masks

As a result of the COVID-19 pandemic, many new materials and masks came onto the market. To determine their suitability, several standards specify which properties to test, including bacterial filtration efficiency (BFE), while none describe how to determine viral filtration efficiency (VFE), a property that is particularly important in times of pandemic. Therefore, we focused our research on evaluating the suitability and efficiency of different systems for determining VFE. Here, we evaluated the VFE of 6 mask types (e.g., a surgical mask, a respirator, material for mask production, and cloth masks) with different filtration efficiencies in four experimental setups and compared the results with BFE results. The study included 17 BFE and 22 VFE experiments with 73 and 81 mask samples tested, respectively. We have shown that the masks tested had high VFE (>99% for surgical masks and respirators, ≥98% for material, and 87-97% for cloth masks) and that all experimental setups provided highly reproducible and reliable VFE results (coefficient of variation < 6%). Therefore, the VFE tests described in this study can be integrated into existing standards for mask testing.

First Insights into the Antiviral Activity of Chitosan-Based Bioactive Polymers towards the Bacteriophage Phi6: Physicochemical Characterization, Inactivation Potential, and Inhibitory Mechanisms

The outbreak of the worrisome coronavirus disease in 2019 has caused great concern among the global public, especially regarding the need for personal protective equipment with applied antiviral agents to reduce the spread and transmission of the virus. Thus, in our research, chitosan-based bioactive polymers as potential antiviral agents were first evaluated as colloidal macromolecular solutions by elemental analysis and charge. Three different types of low and high molecular weight chitosan (LMW Ch, HMW Ch) and a LMW Ch derivative, i.e., quaternary chitosan (quart-LMW Ch), were used. To explore their antiviral activity for subsequent use in the form of coatings, the macromolecular Chs dispersions were incubated with the model virus phi6 (surrogate for SARS-CoV-2), and the success of virus inactivation was determined. Inactivation of phi6 with some chitosan-based compounds was very successful (>6 log), and the mechanisms behind this were explored. The changes in viral morphology after incubation were observed and the changes in infrared bands position were determined. In addition, dynamic and electrophoretic light scattering studies were performed to better understand the interaction between Chs and phi6. The results allowed us to better understand the antiviral mode of action of Chs agents as a function of their physicochemical properties.