Functionalization of cellulosic hydrogels with Cu2O@CuO nanospheres: Toward antifouling applications

Antipathogenic Applications of Copper Nanoparticles in Air Filtration Systems

The COVID-19 pandemic has underscored the critical need for effective air filtration systems in healthcare environments to mitigate the spread of viral and bacterial pathogens. This study explores the utilization of copper nanoparticle-coated materials for air filtration, offering both antiviral and antimicrobial properties. Highly uniform spherical copper oxide nanoparticles (~10 nm) were synthesized via a spinning disc reactor and subsequently functionalized with carboxylated ligands to ensure colloidal stability in aqueous solutions. The functionalized copper oxide nanoparticles were applied as antipathogenic coatings on extruded polyethylene and melt-blown polypropylene fibers to assess their efficacy in air filtration applications. Notably, Type IIR medical facemasks incorporating the copper nanoparticle-coated polyethylene fibers demonstrated a >90% reduction in influenza virus and SARS-CoV-2 within 2 h of exposure. Similarly, heating, ventilation, and air conditioning (HVAC) filtration pre- (polyester) and post (polypropylene)-filtration media were functionalised with the copper nanoparticles and exhibited a 99% reduction in various viral and bacterial strains, including SARS-CoV-2, Pseudomonas aeruginosa, Acinetobacter baumannii, Salmonella enterica, and Escherichia coli. In both cases, this mitigates not only the immediate threat from these pathogens but also the risk of biofouling and secondary risk factors. The assessment of leaching properties confirmed that the copper nanoparticle coatings remained intact on the polymeric fiber surfaces without releasing nanoparticles into the solution or airflow. These findings highlight the potential of nanoparticle-coated materials in developing biocompatible and environmentally friendly air filtration systems for healthcare settings, crucial in combating current and future pandemic threats.

A comprehensive review on the inherent and enhanced antifouling mechanisms of hydrogels and their applications

Biofouling remains a persistent challenge within the domains of biomedicine, tissue engineering, marine industry, and membrane separation processes. Multifunctional hydrogels have garnered substantial attention due to their complex three-dimensional architecture, hydrophilicity, biocompatibility, and flexibility. These hydrogels have shown notable advances across various engineering disciplines. The antifouling efficacy of hydrogels typically covers a range of strategies to mitigate or inhibit the adhesion of particulate matter, biological entities, or extraneous pollutants onto their external or internal surfaces. This review provides a comprehensive review of the antifouling properties and applications of hydrogels. We first focus on elucidating the fundamental principles for the inherent resistance of hydrogels to fouling. This is followed by a comprehensive investigation of the methods employed to enhance the antifouling properties enabled by the hydrogels' composition, network structure, conductivity, photothermal properties, release of reactive oxygen species (ROS), and incorporation of silicon and fluorine compounds. Additionally, we explore the emerging prospects of antifouling hydrogels to alleviate the severe challenges posed by surface contamination, membrane separation and wound dressings. The inclusion of detailed mechanistic insights and the judicious selection of antifouling hydrogels are geared toward identifying extant gaps that must be bridged to meet practical requisites while concurrently addressing long-term antifouling applications.

Robust Electrochemical Biosensors Based on Antifouling Peptide Nanoparticles for Protein Quantification in Complex Biofluids

Peptides with distinct physiochemical properties and biocompatibility hold significant promise across diverse domains including antifouling biosensors. However, the stability of natural antifouling peptides in physiological conditions poses significant challenges to their viability for sustained practical applications. Herein, a unique antifouling peptide FFFGGGEKEKEKEK was designed and self-assembled to form peptide nanoparticles (PNPs), which possessed enhanced stability against enzymatic hydrolysis in biological fluids. The PNP-coated interfaces exhibited superior stability and antifouling properties in preventing adsorption of nonspecific materials, such as proteins and cells in biological samples. Moreover, a highly sensitive and ultralow fouling electrochemical biosensor was developed through the immobilization of the PNPs and specific aptamers onto the polyaniline nanowire-modified electrode, achieving the biomarker carcinoembryonic antigen detection in complex biofluids with reliable accuracy. This research not only addresses the challenge of the poor proteolytic resistance observed in natural peptides but also introduces a universal strategy for constructing ultralow fouling sensing devices.

Chitosan nanofibers encapsulating copper oxide nanoparticles: A new approach towards multifunctional ecological membranes with high antimicrobial and antioxidant efficiency

This paper focuses on the preparation of chitosan-based nanofibers embedding copper oxide nanoparticles to create multifunctional materials that meet the demands of contemporary applications. To this end, a mixture of chitosan, quaternized chitosan and poly (ethylene glycol) was used as polymeric matrix, considering their own contribution to the final material's properties and their ability to stabilize the copper oxide nanoparticles. An exhaustive investigation of the nanofibers was done in order to assess their composition and morphology (FTIR, 1H NMR, WXRD, TGA, SEM, TEM, POM, UV-vis) and to study their mechanical, antimicrobial and antioxidant properties, air and water permeability and ability for air filtration. It was shown that the copper oxide nanoparticles were anchored into the polymeric matrix via strong hydrogen bonding and electrostatic interactions, which induced the improvement of the mechanical properties and antioxidant activity. The copper oxide nanoparticles favored the thinning of the fibers during electrospinning process and improved the antibacterial activity and dust filtration capacity. Besides, the fibers displayed air permeability and vapor water transmission rate similar to synthetic nanofibers, while being biodegradable. All these performances recommend the new materials for developing antibacterial eco-materials with good breathability to be used as hygienic textiles, masks, or air filters.

Nano-CeO2-Loaded Polyzwitterionic Double-Network High-Strength Hydrogel for Highly Enhanced Synergistic Marine Antifouling

Although many antibiofouling materials have been developed based on either bacterial-killing or antiadhesion effects, the integration of both the effects in one material remains challenging for achieving highly enhanced synergistic antibiofouling. In this study, we have explored a nano-CeO2-loaded double-network hydrogel by introducing CeO2 nanorods into a polyzwitterionic hydrogel via a simple one-pot method for achieving highly efficient antifouling. First, the CeO2 nanorods dispersed in the hydrogel, as an outstanding nanozyme, have highly efficient bacterial-killing performance. Second, the superhydrophilic polyzwitterionic hydrogel provides a dense hydrated layer on the surface and subsequently excellent broad-spectrum antiadhesion behavior. Most importantly, the bacterial killing and antiadhesion of this hydrogel can work synergistically to largely improve the marine-antifouling performance. Moreover, the double-network structure of this hydrogel, including the covalently cross-linked polyzwitterion hard network and the physically cross-linked poly(vinyl alcohol) soft network, can provide greatly improved mechanical properties (2.44 MPa of tensile strength reaches and 21.87 MPa of compressive strength). As a result, among the existing marine-antifouling hydrogels, the CeO2-loaded polyzwitterionic double-network hydrogel can achieve outstanding antifouling performance, which can sustain for over 6 months in a real marine environment. This work provides a promising marine-antifouling hydrogel, which will also inspire antifouling research of a new strategy and materials.

β-FeOOH/TiO2/cellulose nanocomposite aerogel as a novel heterogeneous photocatalyst for highly efficient photo-Fenton degradation

The photo-Fenton reaction provides an effective strategy for the removal of organic pollution in water environments. However, it remains a great challenge to develop photo-Fenton catalysts with high photocatalytic activity, low catalyst losses and excellent recyclability. In this work, a β-FeOOH/TiO₂/cellulose nanocomposite aerogel was fabricated as an efficient and convenient heterogeneous catalyst in the photo-Fenton system via in situ synthesis of TiO₂ and β-FeOOH NPs on a cellulose-based aerogel. The cellulose aerogel not only acted as a microreactor to prevent aggregation of particles, but also acted as a supporting material to improve the stability and reusable performance of the catalyst. Meanwhile, the synergy between TiO₂ and β-FeOOH endowed the cellulose-based nanocomposite aerogel with highly efficient photo-Fenton degradation of dyes. As a result, the composite β-FeOOH/TiO₂/cellulose aerogel displayed high photocatalytic performance. Its removal efficiency of MB reached 97.2% under weak UV light for 65 min. There is no obvious decrease in the catalytic efficiency after 5 cycles, suggesting the stability and recyclability of the composite aerogel. This study provides a novel strategy for the preparation of efficient green heterogeneous catalysts by using renewable resources, and shows composite catalyst processes have great potential in wastewater treatment.

BiOI@CeO2@Ti3C2 MXene composite S-scheme photocatalyst with excellent bacteriostatic properties

As an influential antifouling material, photocatalytic materials have drawn attention increasingly over recent years owing to their potential bacteriostatic property in the domain of marine antifouling. Herein, a flower-like BiOI@CeO2@Ti3C2 S-scheme photocatalyst was contrived and prepared by hydrothermal method. The innovative combination of Ti3C2 and narrow band gap semiconductor BiOI was implemented to modify CeO2 and the photocatalytic bacteriostatic mechanism of BiOI@CeO2@Ti3C2 was elucidated. Schottky junction was formed between CeO2 and Ti3C2, and a p-n junction was formed between CeO2 and BiOI. By photoelectrochemical characterization, BCT-10 exhibits the best photoelectrochemical performance of which photogenerated carrier transport can be performed more readily at 10 % CeO2@Ti3C2 addition. 99.76 % and 99.89 % of photocatalytic bacteriostatic efficiency of BCT-10 against Escherichia coli and Staphylococcus aureus were implemented respectively, which were 2.98 and 3.07 times higher than that of pure CeO2. The ternary heterojunction can suppress photogenerated electron-hole complexes more effectively and enhance the photocatalytic bacteriostatic effect of CeO2, which also provided a new concept to the further broadened application of CeO2 in the marine bacteriostatic and antifouling field.

Adhesion advances: from nanomaterials to biomimetic adhesion and applications

The field of adhesion has revealed a significant impact on numerous applications such as wound healing, drug delivery, electrically conductive adhesive, dental adhesive, and wood industry. Nanotechnology has continued to be the primary means to achieve adhesion. Among them, biological systems based on the unique structure of the nano-levels have developed excellent adhesion capabilities after billions of years of evolution and natural selection. Therefore, the research on bionic adhesion inspired by biological systems has gradually emerged. This review firstly focuses on the mechanism of adhesion, and secondly reports the effects of different nanomaterials on adhesion properties. Then based on the structure of mussels, geckos, tree frogs, octopuses, and other organisms, the research progress of biomimetic nanotechnology to achieve adhesion is summarized. Finally, the applications, challenges, and future directions of nanotechnology in new adhesive materials are provided.