Hydro electroactive Cu/Zn coated cotton fiber nonwovens for antibacterial and antiviral applications

Refining and in-situ growth of polyaniline endows the cellulose fibers with electrical stimulation sterilization

Bacteria and virus infections have posed a great threat to public health and personnel safety. For realizing rapid sterilization of the bacteria and virus, electrical stimulation sterilization was adopted to endow cellulose fibers with instantaneous antibacterial and antiviral properties. In the proposed strategy, the fiber is fluffed by mechanical refining, and then by means of the hydrogen bond between hydroxyl and aniline, the polyaniline (PANI) directionally grows vertically along the fine fibers via in-situ oxidative polymerization. Benefiting from the conductive polyaniline nanorod arrays on the fiber stem, the paper made from PANI modified refined fibers (PANI/BCF/P) exhibited excellent antibacterial and antiviral activity, the inhibition rates against S. aureus, E. coli, and bacteriophage MS2 can up to 100 %, 100 %, and 99.89 %, respectively when a weak voltage (2.5 V) was applied within 20 min. This study provides a feasible path for plant fiber to achieve efficient antibacterial and antiviral activity with electrical stimulation, which is of great significance for the preparation of electroactive antibacterial and antiviral green health products.

Regulating molecular brush structure on cotton textiles for efficient antibacterial properties

The molecular brush structures have been developed on cotton textiles for long-term and efficient broad-spectrum antimicrobial performances through the cooperation of alkyl-chain and quaternary ammonium sites. Results show that efficient antibacterial performances can be achieved by the regulation of the alkyl chain length and quaternary ammonium sites. The antibacterial efficiency of the optimized molecular brush structure of [3-(N,N-Dimethylamino)propyl]trimethoxysilane with cetyl modification on cotton textiles (CT-DM-16) can reach more than 99 % against both E. coli and S. aureus. Alkyl-chain grafting displayed significantly improvement in the antibacterial activity against S. aureus with (N,N-Diethyl-3-aminopropyl)trimethoxysilane modification on cotton textiles (CT-DE) based materials. The positive N sites and alkyl chains played important roles in the antibacterial process. Proteomic analysis reveals that the contributions of cytoskeleton and membrane-enclosed lumen in differentially expressed proteins have been increased for the S. aureus antibacterial process, confirming the promoted puncture capacity with alkyl-chain grafting. Theoretical calculations indicate that the positive charge of N sites can be enhanced through alkyl-chain grafting, and the possible distortion of the brush structure in application can further increase the positive charge of N sites. Uncovering the regulation mechanism is considered to be important guidance to develop novel and practical antibacterial materials.

Disulfide bond network crosslinked flexible multifunctional chitosan coating on fabric surface prepared by the chitosan grafted with thioctic acid

In this study, we propose a novel approach to improve the performance of chitosan coating, and thioctic acid with disulfide bonds in its molecular structure was grafted onto the side groups of chitosan macromolecules. The introduction of disulfide bond network cross-linking structure in chitosan coating weakens hydrogen bonds between chitosan macromolecules, causing the macromolecular chains to be more prone to relative motion when subjected to external forces, ultimately improving flexibility of the coating. The modified chitosan becomes more suitable for antibacterial modification in smart wearable fabrics. Subsequently, we fabricated a smart wearable fabric with excellent antibacterial properties and strong electromagnetic shielding by employing the layer-by-layer spraying technique. This involved incorporating chitosan with disulfide bonds and MXene nanoparticles. The fabric surfaces containing chitosan with disulfide bonds exhibited enhanced flexibility compared to unmodified chitosan fabric, resulting in an 8-point improvement in tactile sensation ratings. This research presents a novel approach that simultaneously enhances the electromagnetic shielding effectiveness and efficient antibacterial properties of smart wearable textiles. Consequently, it advances the application of chitosan in the field of antibacterial finishing for functional textiles.

Black Phosphorus - A Rising Star in the Antibacterial Materials

Antibiotics are the most commonly used means to treat bacterial infection at present, but the unreasonable use of antibiotics induces the generation of drug-resistant bacteria, which causes great problems for their clinical application. In recent years, researchers have found that nanomaterials with high specific surface area, special structure, photocatalytic activity and other properties show great potential in bacterial infection control. Among them, black phosphorus (BP), a two-dimensional (2D) nanomaterial, has been widely reported in the treatment of tumor and bone defect due to its excellent biocompatibility and degradability. However, the current theory about the antibacterial properties of BP is still insufficient, and the relevant mechanism of action needs to be further studied. In this paper, we introduced the structure and properties of BP, elaborated the mechanism of BP in bacterial infection, and systematically reviewed the application of BP composite materials in the field of antibacterial. At the same time, we also discussed the challenges faced by the current research and application of BP, which laid a solid theoretical foundation for the further study of BP in the future.

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.

Synergistic Enhancement of Filtering Efficiency and Antibacterial Performance of a Nanofiber Air Filter Decorated with Electropolarized Lithium-Doped ZnO Nanorods

According to clinical case reports, bacterial co-infection with COVID-19 can significantly increase mortality, with Staphylococcus aureus (S. aureus) being one of the most common pathogens causing complications such as pneumonia. Thus, during the pandemic, research on imparting air filters with antibacterial properties was actively initiated, and several antibacterial agents were investigated. However, air filters with inorganic nanostructures on organic nanofibers (NFs) have not been investigated extensively. This study aimed to demonstrate the efficiency of electropolarized poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) NFs decorated with Li-doped ZnO nanorods (NRs) to improve the filtering ability and antibacterial activity of the ultrathin air filter. The surfactant was loaded onto the ZnO─known for its biocompatibility and low toxicity─nanoparticles (NPs) and transferred to the outer surface of the NFs, where Li-doped ZnO NRs were grown. The Li-doped ZnO NR-decorated NF effectively enhanced the physical filtration efficiency and antibacterial properties. Additionally, by exploiting the ferroelectric properties of Li-doped ZnO NRs and PVDF-TrFE NFs, the filter was electropolarized to increase its Coulombic interaction with PMs and S. aureus. As a result, the filter exhibited a 90% PM1.0 removal efficiency and a 99.5% sterilization rate against S. aureus. The method proposed in this study provides an effective route for simultaneously improving the air filter performance and antibacterial activity.

Measuring the quantity of harmful volatile organic compounds inhaled through masks

An increase in the concentration of environmental particulate matter and the spread of the COVID-19 virus have dramatically increased our time spent wearing masks. If harmful chemicals are released from these masks, there may be harmful effects on human health. In this study, the concentration of volatile organic compounds (VOCs) emitted from some commonly used masks was assessed qualitatively and quantitatively under diverse conditions (including different mask material types, time between opening the product and wearing, and mask temperature). In KF94 masks, 1-methoxy-2-propanol (221 ± 356 µg m^-3), N,N-dimethylacetamide (601 ± 450 µg m^-3), n-hexane (268 ± 349 µg m^-3), and 2-butanone (160 ± 244 µg m^-3) were detected at concentrations 22.9-147 times higher than those found in masks made from other materials, such as cotton and other functional fabrics. In addition, in KF94 masks, the total VOC (TVOC) released amounted to 3730 ± 1331 µg m^-3, about 14 times more than that released by the cotton masks (267.5 ± 51.6 µg m^-3). In some KF94 masks, TVOC concentration reached over 4000 µg m^-3, posing a risk to human health (based on indoor air quality guidelines established by the German Environment Agency). Notably, 30 min after KF94 masks were removed from their packaging, TVOC concentrations decreased by about 80% from their initial levels to 724 ± 5.86 µg m^-3; furthermore, 6 h after removal, TVOC concentrations were found to be less than 200 µg m^-3. When the temperature of the KF94 masks was raised to 40 ^oC, TVOC concentrations increased by 119-299%. Since the types and concentrations of VOCs that will be inhaled by mask wearers vary depending on the mask use conditions, it is necessary to comply with safe mask wearing conditions.

Synthesis, characterization and potential applications for oxidized agarose

The knowledge of agarose (AG) oxidation using periodate as oxidizer has not been systematically explored. This paper synthesized oxidized agarose (OAG) using solid-sate and solution reaction methods; the reaction mechanism and the properties of OAG samples were systematically evaluated. Chemical structure analysis disclosed that the aldehyde group and carboxyl group contents in all OAG samples are extremely low. Meanwhile, crystallinity, dynamic viscosity and molecular weight of OAG samples is lower than that of the original AG. Reaction temperature, time and sodium periodate dosage are inversely proportional to the decline of the gelling temperature (Tg) and melting temperature (Tm); and the Tg and Tm for the OAG sample obtained are even 19 °C and 22 °C lower than that of the original AG. The as-synthesized OAG samples all possess excellent cytocompatibility and blood compatibility; and can promote the proliferation and migration of fibroblast cells. Last but not least, the gel strength, hardness, cohesiveness, springiness and chewiness of the OAG gel can be effectively regulated via oxidation reaction. In conclusions, both solid and solution oxidation can regulate the physical properties of OAG and enlarge its potential applications in wound dressing, tissue engineering and food areas.

Green preparation of silver nanocluster composite AgNCs@CF-g-PAA and its application: 4-NP catalytic reduction and hydrogen production

4-Nitrophenol (4-NP) is a serious organic environmental pollutant. Conversion of 4-nitrophenol to 4-aminophenol (4-AP) by catalytic hydrogenation is an effective solution. In this work, a catalyst (AgNCs@CF-g-PAA) loaded with silver nanoclusters (AgNCs) was prepared by radiation technique. Firstly, the template polyacrylic acid (PAA) was grafted onto the cotton fiber (CF) by radiation grafting technique to obtain a solid template (CF-g-PAA). After that, AgNCs were synthesized in situ on CF-g-PAA by radiation reduction, and the composite material AgNCs@CF-g-PAA was obtained directly. AgNCs@CF-g-PAA has an obvious photoluminescence phenomenon, which is attributed to the stable AgNCs binding to the carboxyl on the PAA molecular chain. Due to the extremely small size of AgNCs, AgNCs@CF-g-PAA has good catalytic characteristics. The prepared AgNCs@CF-g-PAA catalyst has a very high catalytic rate for the hydrogenation of 4-NP. Even at high concentrations of 4-NP, AgNCs@CF-g-PAA can still maintain a high catalytic rate. At the same time, the AgNCs@CF-g-PAA catalyst can also be used to catalyze the rapid hydrolysis of sodium borohydride, which is conducive to hydrogen production. In summary, we have prepared a practical catalyst AgNCs@CF-g-PAA with high catalytic performance based on cheap raw materials and a simple synthesis route, which provides a catalyst candidate for the treatment of water contaminant 4-NP and the production of hydrogen from sodium borohydride.

Asymmetric wettable polycaprolactone-chitosan/chitosan oligosaccharide nanofibrous membrane as antibacterial dressings

Wound infection and inflammation hinder the process of wound healing and bother human beings chronically. As a naturally degradable macromolecule, chitosan (CS) has been widely used in antibacterial wound dressings. However, the antibacterial property of chitosan is inhibited by its water insolubility. In this study, we prepared a bilayered asymmetric nanofibrous membrane with the hydrophilic CS/chitosan oligosaccharide (COS) nanofibrous membrane as the bottom layer and the hydrophobic polycaprolactone (PCL) nanofibrous membrane as the top layer. Results showed that incorporating COS improved the CS membrane's wettability, and adding 0.5 % COS increased the inhibition zone diameter of Escherichia coli and Staphylococcus aureus by 23 % and 26 %, respectively. Moreover, the PCL layer could prevent the adhesion of water and bacteria. The PCL-CS/COS_0.5% membrane showed relatively good mechanical properties, excellent water absorptivity (460 %), and appropriate cytocompatibility. This asymmetric wettable membrane has a massive potential to serve as a new antibacterial dressing for wound healing.

Sprayable surface-adaptive biocompatible membranes for efficient hemostasis via assembly of chitosan and polyphosphate

This work describes a hemostatic membrane system (or surface coating) based on spray-assisted layer-by-layer electrostatic assemblies of oppositely charged polyphosphate (polyP) and chitosan (Cs). The as-prepared membrane formed a robust micro-stratified porous structure with high flexibility. Both blood clotting test and rodent hepatic severe hemorrhage model revealed the excellent hemostatic performance of the membrane system, benefitting from the robust assembly and synergistic effect of polyP/Cs as well as membrane surface chemistry. Compared to Cs-topped membrane surface, polyP-sprayed one exhibited further improved hemostatic effect via promoting fibrin formation. Besides, comprehensive in vitro and in vivo evaluations demonstrated good biocompatibility and biodegradability of the membrane. The present approach that integrated the hemostasis-stimulating capability of polyP/Cs with facile spraying method is highly scalable and flexible, which is envisioned to be adapted readily for other hemostatic polyelectrolytes and surface functionalization of diverse existing hemostatic products on demand.

Tannic acid-crosslinked O-carboxymethyl chitosan hydrogels for enhanced antibacterial activity and rapid hemostasis

Bacterial infection and massive blood loss are major challenges for global public health. Herein, a series of tannic acid encapsulated O-carboxymethyl chitosan (CMC) based hydrogels were prepared using a facile approach for both hemorrhage control and effective anti-bacterium. The results indicated that the tannic acid-cosslinked CMC hydrogels had excellent mechanical property, swelling ability as well as great cytocompatibility. Comparably, with increasing tannic acid loading, the bleeding control and antibacterial performance against both E. coli and S. aureus were improved simultaneously, especially for the 5% tannic acid-cosslinked CMC hydrogel. Moreover, the prepared CMC hydrogel loading with tannic acid could induce hemocytes and platelets aggregation, promote the blood clotting and achieve bleeding control in vivo due to the interconnected fibrous web structure and the chemical activation (the phenol group of tannic acid). Thus, the resultant CMC hydrogel enabled the maintenance of high bioavailability of tannic acid and synchronization with the interconnected fibrous structure of CMC hydrogels, which was expected to be a promising candidate for robust and safe hemostatic dressings.

Polyvinylidene fluoride multi-scale nanofibrous membrane modified using N-halamine with high filtration efficiency and durable antibacterial properties for air filtration

HYPOTHESIS

Particulate matter (PM) pollution and the coronavirus (COVID-19) pandemic have increased demand for protective masks. However, typical protective masks only intercept particles and produce peculiar odors if worn for extended periods owing to bacterial growth. Therefore, new protective materials with good filtration and antibacterial capabilities are required.

EXPERIMENTS

In this study, we prepared multi-scale polyvinylidene fluoride (PVDF) nanofibrous membranes for efficient filtration and durable antibacterial properties via N-halamine modification.

FINDINGS

The N-halamine-modified nanofibrous membrane (PVDF-PAA-TMP-Cl) had sufficient active chlorine content (800 ppm), and the tensile stress and strain were improved compared with the original membrane, from 6.282 to 9.435 MPa and from 51.3 % to 56.4 %, respectively. To further improve the interception efficiency, ultrafine nanofibers (20-35 nm) were spun on PVDF-PAA-TMP-Cl nanofibrous membranes, and multi-scale PVDF-PAA-TMP-Cl nanofibrous membranes were prepared. These membranes exhibited good PM_0.3 interception (99.93 %), low air resistance (79 Pa), promising long-term PM_2.5 purification ability, and high bactericidal efficiency (>98 %). After ten chlorination cycles, the antibacterial efficiency against Escherichia coli and Staphylococcus aureus exceeded 90 %; hence, the material demonstrated highly efficient filtration and repeatable antibacterial properties. The results of this study have implications for the development of air and water filtration systems and multi-functional protective materials.

Nano-antivirals: A comprehensive review

Nanoparticles can be used as inhibitory agents against various microorganisms, including bacteria, algae, archaea, fungi, and a huge class of viruses. The mechanism of action includes inhibiting the function of the cell membrane/stopping the synthesis of the cell membrane, disturbing the transduction of energy, producing toxic reactive oxygen species (ROS), and inhibiting or reducing RNA and DNA production. Various nanomaterials, including different metallic, silicon, and carbon-based nanomaterials and nanoarchitectures, have been successfully used against different viruses. Recent research strongly agrees that these nanoarchitecture-based virucidal materials (nano-antivirals) have shown activity in the solid state. Therefore, they are very useful in the development of several products, such as fabric and high-touch surfaces. This review thoroughly and critically identifies recently developed nano-antivirals and their products, nano-antiviral deposition methods on various substrates, and possible mechanisms of action. By considering the commercial viability of nano-antivirals, recommendations are made to develop scalable and sustainable nano-antiviral products with contact-killing properties.

One-step Green Fabrication of Antimicrobial Surfaces via In Situ Growth of Copper Oxide Nanoparticles

Microorganisms such as pathogenic bacteria, fungi, and viruses pose a serious threat to human health and society. Surfaces are one of the major pathways for the transmission of infectious diseases. Therefore, imparting antipathogenic properties to these surfaces is significant. Here, we present a rapid, one-step approach for practical fabrication of antimicrobial and antifungal surfaces using an eco-friendly and low-cost reducing agent, the extract of Cedrus libani. Copper oxide nanoparticles were grown in situ on the surface of print paper and fabric in the presence of the copper salt and extract, without the use of any additional chemicals. The morphology and composition of the grown nanoparticles were characterized using field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction techniques. The analysis revealed that the grown particles consist of mainly spherical CuO nanoparticles with an average size of ∼14 nm and its clusters with an average size of ∼700 nm. The in situ growth process enables strong bonding of the nanoparticles to the surface, resulting in enhanced durability against wear and tear. Moreover, the fabricated surface shows excellent growth inhibition ability and bactericidal activity against both gram-negative and gram-positive bacteria, Escherichia coli and Staphylococcus aureus, as well as antifungal activity against Candida albicans, a common pathogenic fungus. The ability to grow copper oxide nanoparticles on different surfaces paves the way for a range of applications in wound dressings, masks, and protective medical equipment.