Cuprous oxide nanoparticles (Cu2ONPs) were used for preparing composites with linear low-density polyethylene (LLDPE) by co-extrusion, thermal adhesion, and attachment using ethyl cyanoacrylate, trimethoxyvinylsilane, and epoxy resin. The composites were examined by Scanning electron microscope and tested for their antibacterial activity against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. All of these composites—except for the one obtained by extrusion—eradicated cells of both bacteria within half an hour. The composite prepared by thermal adhesion of Cu2ONPs on LLDPE had the highest external exposure of nanoparticles and exhibited the highest activity against the bacteria. This composite and the one obtained using ethyl cyanoacrylate showed no leaching of copper ions into the aqueous phase. Copper ion leaching from composites prepared with trimethoxyvinylsilane and epoxy resin was very low. The antibacterial activity of the composites can be rated as follows: obtained by thermal adhesion > obtained using ethyl cyanoacrylate > obtained using trimethoxyvinylsilane > obtained using epoxy resin > obtained by extrusion. The composites with the highest activity are potential materials for tap water and wastewater disinfection.

Prussian blue analogs (PBAs) are well-known artificial enzymes with peroxidase (PO)-like activity. PBAs have a high potential for applications in scientific investigations, industry, ecology and medicine. Being stable and both catalytically and electrochemically active, PBAs are promising in the construction of biosensors and biofuel cells. The “green” synthesis of PO-like PBAs using oxido-reductase flavocytochrome b2 is described in this study. When immobilized on graphite electrodes (GEs), the obtained green-synthesized PBAs or hexacyanoferrates (gHCFs) of transition and noble metals produced amperometric signals in response to H2O2. HCFs of copper, iron, palladium and other metals were synthesized and characterized by structure, size, catalytic properties and electro-mediator activities. The gCuHCF, as the most effective PO mimetic with a flower-like micro/nano superstructure, was used as an H2O2-sensitive platform for the development of a glucose oxidase (GO)-based biosensor. The GO/gCuHCF/GE biosensor exhibited high sensitivity (710 A M−1m−2), a broad linear range and good selectivity when tested on real samples of fruit juices. We propose that the gCuHCF and other gHCFs synthesized via enzymes may be used as artificial POs in amperometric oxidase-based (bio)sensors.

Consumption of contaminated water may lead to dangerous and even fatal water-borne diseases. Disinfection of drinking water is the most effective solution for this problem. The most common water treatment methods are based on the use of toxic disinfectants. Composites of polymers with nanosized metals and their oxides may become a good alternative to the existing methods. Expanding the scope of our previous publication, copper, cuprous, and copper oxide nanoparticles were immobilized onto linear low-density polyethylene by a simple thermal adhesion method. The antibacterial efficiency of the immobilized nanoparticles was tested against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus in batch experiments and for the first time the efficiency of these composites is reported for continuous flow regime. Immobilized copper and cuprous oxide nanoparticles demonstrated a high ability to eradicate bacteria after 30 min. These composites showed no or very limited leaching of copper ions into the aqueous phase both in the presence and in the absence of a bacterial suspension. Immobilized copper and cuprous oxide nanoparticles can be used for batch or continuous disinfection of water.

Photosensitizers (PSs) are known as powerful antibacterial agents that are activated by direct exposure to visible light. PSs can be noncovalently entrapped into the silica gel network for their controlled release into a contaminated area. The immobilization of PS-containing gel matrices on a polymer support expands their possible applications, such as antibacterial surfaces and coatings, which can be used for the disinfection of liquids. In the current study, we report the use of Rose Bengal (RB) incorporated into organically modified silica matrices (RB@ORMOSIL matrices) by the sol-gel technique. The RB matrices exhibit high activity against Gram-positive and Gram-negative bacteria under illumination by white light. The amount and timing of solidifier addition to the matrix affected the interaction of the latter with the RB, which in turn could affect the antibacterial activity of RB. The most active specimen against both Gram-positive and Gram-negative bacterial cells was the RB6@ORMOSIL matrix immobilized on a linear low-density polyethylene surface, which was prepared by an easy, cost-effective, and simple thermal adhesion method. This specimen, RB6@OR@LLDPE, showed the low release of RB in an aqueous environment, and exhibited high long-term antibacterial activity in at least 14 rounds of recycled use against S. aureus and in 11 rounds against E. coli.

Nanozymes (NZs) are catalytically active nanomaterials that have enzyme-like activity but possess increased stability and greater availability due to the fact of their simpler preparation technologies. Nanozymes as nanoscale artificial enzymes demonstrate various catalytic specificities as oxidoreductases, such as peroxidase, catalase, laccase, and others as well as hydrolases, proteases, endonucleases, DNA-ases, NO synthases, etc. A broad variety of NZs exhibits dual- or multienzyme mimetic activity. Nanozymes as stable, low-cost mimetics of natural enzymes have a high potential for application in different branches of biotechnology including scientific investigations, industry, and ecology. Nanozymes can be applied in medicine as diagnostic tools and components of therapeutic drugs. Since NZs have high catalytic activity and chemical and biological stability, they are very promising in the construction of biosensors and biofuel cells. For these reasons, the search for simple methods of synthesis and characterization of different NZs is a very important and real problem. The “green” synthesis of Prussian blue analogous as peroxidase-like NZs using oxido-reductases is described in this study. The obtained green-synthesized hexacyanoferrates (gHCFs) of transition metals were characterized by structure, size, composition, catalytic properties, electro-mediator activities, and substrate specificity. Copper hexacyanoferrate (gCuHCF) was studied in more detail. When immobilized on a graphite electrode (GE), gCuHCF under special conditions of pH and tension gave amperometric signals on hydrogen peroxide and can be used as a peroxidase mimetic in oxidase-based biosensors. Under other conditions, gCuHCF/GE reacts to other analytes. We propose that gHCFs of transition metals synthesized via enzymes may become prospect platforms for the construction of multi-functional amperometric (bio)sensors.