Coating Technologies for Copper Based Antimicrobial Active Surfaces: A Perspective Review

Bioresorbable Polyester Coatings with Antifouling and Antimicrobial Properties for Prevention of Biofilm Formation in Early Stage Infections on Ti6Al4V Hard-Tissue Implants

Implants made from titanium are used as prostheses because of their biocompatibility and their mechanical properties close to those of human bone. However, the risk of bacterial infection is always a major concern during surgery, and the development of biofilm can make these infections difficult to treat. A promising strategy to mitigate against bacterial infections is the use of antifouling and antimicrobial coatings, where bioresorbable polymers can play an important role due to their controlled degradability and sustained drug release, as well as excellent biocompatibility. In the present study, poly(d,l-lactide) (PDLLA) and poly[d,l-lactide-co-methyl ether poly(ethylene glycol)] (PDLLA-PEG) were studied, varying the PEG content (20-40% w/w) to analyze the effectiveness of PEG as an antifouling molecule. In addition, silver sulfadiazine (AgSD) was used as an additional antimicrobial agent with a concentration ≤5% w/w and incorporated into the PEGylated polymers to create a polymer with both antifouling and antimicrobial properties. Polymers synthesized were applied using spin coating to obtain homogeneous coatings to protect samples made from titanium/aluminum/vanadium (Ti6Al4V). The polymer coatings had a smoothing effect in comparison to that of the uncoated material, decreasing the contact area available for bacterial colonization. It was also noted that PEG addition into the polymeric chain developed amphiphilic materials with a decrease in contact angle from the most hydrophobic (Ti6Al4V) to the most hydrophilic PDLLA-PEG (60/40), highlighting the increase in water uptake contributing to the hydration layer formation, which confers the antifouling effect on the coating. This study demonstrated that the addition of PEG above 20% w/w and AgSD above 1% w/v into the formulation was able to decrease bacterial adherence against clinically relevant biofilm former strains Staphylococcus aureus and Pseudomonas aeruginosa.

Anti-Microbial, Thermal, Mechanical, and Gas Barrier Properties of Linear Low-Density Polyethylene Extrusion Blow-Molded Bottles

Microbial contamination can occur on the surfaces of blow-molded bottles, necessitating the development and application of effective anti-microbial treatments to mitigate the hazards associated with microbial growth. In this study, new methods of incorporating anti-microbial particles into linear low-density polyethylene (LLDPE) extrusion blow-molded bottles were developed. The anti-microbial particles were thermally embossed on the external surface of the bottle through two particle deposition approaches (spray and powder) over the mold cavity. The produced bottles were studied for their thermal, mechanical, gas barrier, and anti-microbial properties. Both deposition approaches indicated a significant enhancement in anti-microbial activity, as well as barrier properties, while maintaining thermal and mechanical performance. Considering both the effect of anti-microbial agents and variations in tensile bar weight and thickness, the statistical analysis of the mechanical properties showed that applying the anti-microbial agents had no significant influence on the tensile properties of the blow-molded bottles. The external fixation of the particles over the surface of the bottles would result in optimum anti-microbial activity, making it a cost-effective solution compared to conventional compounding processing.

Nanosynthesis, phycochemical constituents, and pharmacological properties of cyanobacterium Oscillatoria sp

The Oscillatoria sp., a blue-green alga or cyanobacterium, consists of about 305 species distributed globally. Cyanobacteria are prokaryotes possessing several secondary metabolites that have industrial and biomedical applications. Particularly, the published reviews on Oscillatoria sp. have not recorded any pharmacology, or possible details, while the detailed chemical structures of the alga are reported in the literature. Hence, this study considers pertinent pharmacological activities of the plethora of bioactive components of Oscillatoria sp. Furthermore, the metallic nanoparticles produced with Oscillatoria sp. were documented for plausible antibacterial, antifungal, antioxidant, anticancer, and cytotoxic effects against several cultured human cell lines. The antimicrobial activities of solvent extracts of Oscillatoria sp. and the biotic activities of its derivatives, pyridine, acridine, fatty acids, and triazine were structurally described in detail. To understand the connotations with research gaps and provide some pertinent prospective suggestions for further research on cyanobacteria as potent sources of pharmaceutical utilities, attempts were documented. The compounds of Oscillatoria sp. are a potent source of secondary metabolites that inhibit the cancer cell lines, in vitro. It could be expected that by holistic exploitation, the natural Oscillatoria products, as the source of chemical varieties and comparatively more potent inhibitors, would be explored against pharmacological activities with the integument of SARs.

Self-Assembly of a Dipeptide with a Reduced Amount of Copper into Antifungal and Antibacterial Particles

With the growing concern over the environmental impact and health risks associated with conventional pesticides, there is a great need for developing safer and more sustainable alternatives. This study demonstrates the self-assembly of antimicrobial and antifungal spherical particles by a dipeptide utilizing a reduced amount of copper salt compared to the commonly employed formulation. The particles can be sprayed on a surface and form an antimicrobial coating. The effectiveness of the coating against the bacteria Pectobacterium brasiliense, a common pathogen affecting potato crops, was demonstrated, as the coating reduced the bacterial load by 7.3 log. Moreover, a comprehensive field trial was conducted, where the formulation was applied to potato seeds. Remarkably, it exhibited good efficacy against three prevalent potato pathogens (P. brasiliense, Pythium spp., and Spongospora subterranea) while demonstrating no phytotoxic effects on the potatoes. These findings highlight the tremendous potential of this formulation as a nonphytotoxic alternative to replace hazardous pesticides currently available in the market.

Unraveling the Role of Metals and Organic Acids in Bacterial Antimicrobial Resistance in the Food Chain

Antimicrobial resistance (AMR) has a significant impact on human, animal, and environmental health, being spread in diverse settings. Antibiotic misuse and overuse in the food chain are widely recognized as primary drivers of antibiotic-resistant bacteria. However, other antimicrobials, such as metals and organic acids, commonly present in agri-food environments (e.g., in feed, biocides, or as long-term pollutants), may also contribute to this global public health problem, although this remains a debatable topic owing to limited data. This review aims to provide insights into the current role of metals (i.e., copper, arsenic, and mercury) and organic acids in the emergence and spread of AMR in the food chain. Based on a thorough literature review, this study adopts a unique integrative approach, analyzing in detail the known antimicrobial mechanisms of metals and organic acids, as well as the molecular adaptive tolerance strategies developed by diverse bacteria to overcome their action. Additionally, the interplay between the tolerance to metals or organic acids and AMR is explored, with particular focus on co-selection events. Through a comprehensive analysis, this review highlights potential silent drivers of AMR within the food chain and the need for further research at molecular and epidemiological levels across different food contexts worldwide.

Incorporation of Copper Nanoparticles on Electrospun Polyurethane Membrane Fibers by a Spray Method

Electrospinning is an easy and versatile technique to obtain nanofibrous membranes with nanosized fibers, high porosity, and pore interconnectivity. Metal nanoparticles (e.g., Ag, Cu, ZnO) exhibit excellent biocide properties due to their size, shape, release of metal ions, or reactive oxygen species production, and thus are often used as antimicrobial agents. In this study, a combined electrospinning/spray technique was employed to fabricate electrospun polyurethane membranes loaded with copper nanoparticles at different surface densities (10, 20, 25, or 30 μg/cm2). This method allows particle deposition onto the surface of the membranes without the use of chemical agents. SEM images showed that polyurethane fibers own homogeneous thickness (around 650 nm), and that spray-deposited copper nanoparticles are evenly distributed. STEM-EDX demonstrated that copper nanoparticles are deposited onto the surface of the fibers and are not covered by polyurethane. Moreover, a uniaxial rupture test showed that particles are firmly anchored to the electrospun fibers. Antibacterial tests against model microorganisms Escherichia coli indicated that the prepared electrospun membranes possess good bactericidal effect. Finally, the antiviral activity against SARS-CoV-2 was about 90% after 1 h of direct contact. The obtained results suggested that the electrospun membranes possess antimicrobial activities and can be used in medical and industrial applications.

Facile Implementation of Antimicrobial Coatings through Adhesive Films (Wraps) Demonstrated with Cuprous Oxide Coatings

Antimicrobial coatings have a finite lifetime because of wear, depletion of the active ingredient, or surface contamination that produces a barrier between the pathogen and the active ingredient. The limited lifetime means that facile replacement is important. Here, we describe a generic method for rapidly applying and reapplying antimicrobial coatings to common-touch surfaces. The method is to deposit an antimicrobial coating on a generic adhesive film (wrap), and then to attach that modified wrap to the common-touch surface. In this scenario, the adhesion of the wrap and antimicrobial efficacy are separated and can be optimized independently. We demonstrate the fabrication of two antimicrobial wraps, both using cuprous oxide (Cu₂O) as the active ingredient. The first uses polyurethane (PU) as the polymeric binder and the second uses polydopamine (PDA). Our antimicrobial PU/Cu₂O and PDA/Cu₂O wraps, respectively, kill >99.98% and >99.82% of the human pathogen, P. aeruginosa, in only 10 min, and each of them kill >99.99% of the bacterium in 20 min. These antimicrobial wraps can be removed and replaced on the same object in <1 min with no tools. Wraps are already frequently used by consumers to coat drawers or cars for aesthetic or protective purposes.

Antibacterial and Antibiofilm Activity of Nanostructured Copper Films Prepared by Ionized Jet Deposition

Metal coatings represent good strategies to functionalize surfaces/devices and limit bacterial contamination/colonization thanks to their pleiotropic activity and their ability to prevent the biofilm formation. Here, we investigated the antibacterial and antibiofilm capacity of copper coatings deposited through the Ionized Jet Deposition (IJD) on the Calgary Biofilm Device (CBD) against the growth of two gram-negative and two gram-positive pathogenic strains. Three areas (i.e., (+)Cu, (++)Cu, and (+++)Cu based on the metal amount) on the CBD were obtained, presenting nanostructured coatings with high surface homogeneity and increasing dimensions of aggregates from the CBD periphery to the centre. The coatings in (++)Cu and (+++)Cu were efficient against the planktonic growth of the four pathogens. This antibacterial effect decreased in (+)Cu but was still significant for most of the pathogens. The antibiofilm efficacy was significant for all the strains and on both coated and uncoated surfaces in (+++)Cu, whereas in (++)Cu the only biofilms forming on the coated surfaces were inhibited, suggesting that the decrease of the metal on the coatings was associated to a reduced metal ion release. In conclusion, this work demonstrates that Cu coatings deposited by IJD have antibacterial and antibiofilm activity against a broad range of pathogens indicating their possible application to functionalize biomedical devices.

Magnetron Sputtering of Transition Metals as an Alternative Production Means for Antibacterial Surfaces

In the light of the SARS-CoV-2 pandemic and growing numbers of bacteria with resistance to antibiotics, the development of antimicrobial coatings is rising worldwide. Inorganic coatings are attractive because of low environmental leakage and wear resistance. Examples for coatings are hot metal dipping or physical vapor deposition of nanometer coatings. Here, magnetron sputtering of various transition metals, such as gold, ruthenium and tantalum, was investigated. Metal films were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy (EDX). We investigated the growth of Pseudomonas aeruginosa isolated from household appliances on different sputter-coated metal surfaces. The fine-grained nanometric structure of these metal coatings was between 14 nm (tantalum) and 26 nm (gold) and the roughness was in a range of 164 pm (ruthenium) to 246 pm (gold). Antibacterial efficacy of metal surfaces followed the order: gold > tantalum > ruthenium. Interestingly, gold had the strongest inhibitory effect on bacterial growth, as analyzed by LIVE/DEAD and CFU assay. High-magnification SEM images showed dead bacteria characterized by shrinkage induced by metal coatings. We conclude that sputtering might be a new application for the development of antimicrobial surfaces on household appliances and or surgical instruments.

Highly Durable Antimicrobial Tantalum Nitride/Copper Coatings on Stainless Steel Deposited by Pulsed Magnetron Sputtering

Highly durable and antimicrobial tantalum nitride/copper (TaN/Cu) nanocomposite coatings were deposited on D-9 stainless steel substrates by pulsed magnetron sputtering. The Cu content in the coating was varied in the range of 1.42-35.42 atomic % (at.%). The coatings were characterized by electron probe microanalyzer, X-ray diffraction, scanning electron microscope and atomic force microscope. The antibacterial properties of the TaN/Cu coatings against gram-negative Pseudomonas aeruginosa were evaluated using a cell culture test. The peak hardness and Young's modulus of TaN/Cu with 10.46 at.% Cu were 24 and 295 GPa, respectively, which amounted to 15 and 41.67% higher than Cu-free TaN. Among all, TaN/Cu with 10.46 at.% exhibited the lowest friction coefficient. The TaN/Cu coatings exhibited significantly higher antibacterial activity than Cu-free TaN against Pseudomonas aeruginosa. On TaN, the bacterial count was about 4 × 10⁶ CFU, whereas it was dropped to 1.2 × 10² CFU in case of TaN/Cu with 10.46 at.% Cu. The bacterial count was decreased from 9 to 6 when the Cu content increased from 25.54 to 30.04 at.%. Live bacterial cells were observed in the SEM images of TaN, and dead cells were found on TaN/Cu. Overall, TaN/Cu with 10.46 at.% Cu was found to be a potential coating composition in terms of higher antimicrobial activity and mechanical durability.

Synthesis, and characterization of metallic glassy Cu-Zr-Ni powders decorated with big cube Zr2Ni nanoparticles for potential antibiofilm coating applications

Biofilms, are significant component that contributes to the development of chronic infections, especially when medical devices are involved. This issue offers a huge challenge for the medical community since standard antibiotics are only capable of eradicating biofilms to a very limited degree. The prevention of biofilm formation have led to the development of a variety of coating methods and new materials. These methods are intended to coat surfaces in such a way as to inhibit the formation of biofilm. Metallic glassy alloys, in particular, alloys that include copper and titanium metals have gained popularity as desirable antibacterial coating. Meanwhile, there has been a rise in the use of the cold spray coating technique due to the fact that it is a proper approach for processing temperature-sensitive materials. The present study was carried out in part with the intention of developing a new antibiofilm metallic glassy consisting of ternary Cu–Zr–Ni using mechanical alloying technique. The spherical powders that comprised the end-product were utilized as feedstock materials for cold spray coatings to stainless steel surfaces at low temperature. When compared to stainless steel, substrates coated with metallic glassy were able to significantly reduce the formation of biofilm by at least one log.

The Effect of Cu Additions on the Antibacterial Properties of Metallic Glassy Ni50TM50 (TM; Ti, Zr) Binary Systems

Antibacterial agents derived from classic organic compounds have been frequently employed for a number of years as a protective layer for biofilms. On the other hand, these agents often comprise dangerous components that, due to their interaction with toxic compounds, may be damaging to human beings. This hazard may be caused by the agents’ proximity to the toxic substances. Over the course of the past three decades, a variety of approaches, such as the utilization of a broad spectrum of metallic and oxide materials, have been the subject of research in order to develop a diverse selection of antibacterial coating layers that are acceptable. One of these approaches is the use of silver nanoparticles. It has been established that the cold spray technique, a solid-state method compatible with nanopowders, has shown higher performance and is the most effective strategy for coating materials. This has been proven via testing. It is possible to produce one-of-a-kind material coatings in ways that are not even remotely imaginable with any other thermal coating method, which is the primary reason for its prominence in contemporary production. The capacity to do so is what provides it with an advantage over its rivals in the market. This current study was conducted, in part, to investigate the effects of Cu-alloying elements on the antibacterial behavior of metallic glassy alloys on Ni50TM50 (TM; Ti, Zr) and Cu50TM40Ni10 (TM; Ti, Zr) systems prepared by the mechanical disordering technique, in conjunction with the cold spray method. These alloys were created by combining the mechanical disordering technique with the cold spray method. The arc melting process was employed to generate master alloys consisting of Ni50Ti50, Ni50Zr50, Cu50Ti40Ni10, and Cu50Zr40Ni10 for the purpose of this investigation. The master alloys were then used as feedstock materials for the creation of metallic glassy powders. Following the pulverization of the alloys of each system into a powdered form, the mixtures were charged through a high-energy ball milling operation for a duration of 50 h. Using the cold spray technique, the as-milled powders, which were metallic glasses, were applied singly in order to coat SUS304 sheets. The method was employed for this purpose. After the addition of Cu to the two binary Ni50TM50 (TM; Ti, Zr) alloys, the antibacterial properties of their corresponding metallic glassy phases were found to be significantly enhanced. This was shown by the fact that they were successful in preventing the development of biofilm by E. coli in contrast to the other systems that were evaluated.

Mechanical Alloying Integrated with Cold Spray Coating for Fabrication Cu50(Ti50-xNix), x; 10, 20, 30, and 40 at.% Antibiofilm Metallic Glass Coated/SUS304 Sheets

Antibacterial agents derived from conventional organic compounds have traditionally been employed as a biofilm protective coating for many years. These agents, on the other hand, often include toxic components that are potentially hazardous to humans. Multiple approaches have been investigated over the last two decades, including the use of various metallic and oxide materials, in order to produce a diverse variety of usable coating layers. When it comes to material coating approaches, the cold spray technique, which is a solid-state method that works well with nanopowders, has shown superior performance. Its capacity to produce unique material coating in ways that are not possible with other thermal methods is the primary reason for its importance in contemporary production. The present work has been addressed in part to explore the possibility of employing mechanically alloyed Cu50(Ti50-xNix)x; x = 10, 20, 30, and 40 at.% metallic glass powders, for producing an antibiofilm/SUS304 surface protective coating, using the cold spray approach. In this study, elemental Cu, Ti, and Ni powders were low-energy ball milled for 100 h to fabricate metallic glassy powders with different Ni contents. The as-prepared metallic glassy powders were utilized to coat SUS304 sheets, using the cold spraying process. With high nanohardness values, the as-fabricated coating material, in particular Cu50Ti20Ni30, demonstrated remarkable performance in comparison to other materials in its class. Furthermore, it displayed excellent wear resistance while maintaining a low coefficient of friction, with values ranging from 0.32 to 0.45 in the tested range. E. coli biofilms were formed on 20 mm2 SUS304 sheet coated coupons, which had been injected with 1.5 108 CFU mL-1 of the bacterium. With the use of nanocrystalline Cu-based powders, it is feasible to achieve considerable biofilm inhibition, which is a practical strategy for accomplishing the suppression of biofilm formation.

Copper Surface Treatment Method with Antibacterial Performance Using "Super-Spread Wetting" Properties

In this work, a copper coating is developed on a carbon steel substrate by exploiting the superwetting properties of liquid copper. We characterize the surface morphology, chemical composition, roughness, wettability, ability to release a copper ion from surfaces, and antibacterial efficacy (against Escherichia coli and Staphylococcus aureus). The coating shows a dense microstructure and good adhesion, with thicknesses of approximately 20–40 µm. X-ray diffraction (XRD) analysis reveals that the coated surface structure is composed of Cu, Cu₂O, and CuO. The surface roughness and contact angle measurements suggest that the copper coating is rougher and more hydrophobic than the substrate. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) measurements reveal a dissolution of copper ions in chloride-containing environments. The antibacterial test shows that the copper coating achieves a 99.99% reduction of E. coli and S. aureus. This study suggests that the characteristics of the copper-coated surface, including the chemical composition, high surface roughness, good wettability, and ability for copper ion release, may result in surfaces with antibacterial properties.

Fabrication of Antibacterial Metal Surfaces Using Magnetron-Sputtering Method

One-hundred-nanometer films consisting of silver, copper, and gold nanocrystallites were prepared, and their antibacterial properties were quantitatively measured. The magnetron-sputtering method was used for the preparation of the metallic films over the glass plate. Single- and double-layer films were manufactured. The films were thoroughly characterized with the XRD, SEM, EDS, and XPS methods. The antibacterial activity of the samples was investigated. Gram-negative Escherichia coli, strain K12 ATCC 25922 (E. coli), and Gram-positive Staphylococcus epidermidis, ATCC 49461 (S. epidermidis), were used in the microbial tests. The crystallite size was about 30 nm in the cases of silver and gold and a few nanometers in the case of copper. Significant oxidation of the copper films was proven. The antibacterial efficacy of the tested samples followed the order: Ag/Cu > Au/Cu > Cu. It was concluded that such metallic surfaces may be applied as contact-killing materials for a more effective fight against bacteria and viruses.