Nanostructured Copper Surface Kills ESKAPE Pathogens and Viruses in Minutes

Dual Antibacterial Properties of Copper-Coated Nanotextured Stainless Steel

Bacterial adhesion to stainless steel, an alloy commonly used in shared settings, numerous medical devices, and food and beverage sectors, can give rise to serious infections, ultimately leading to morbidity, mortality, and significant healthcare expenses. In this study, Cu-coated nanotextured stainless steel (nSS) fabrication have been demonstrated using electrochemical technique and its potential as an antibiotic-free biocidal surface against Gram-positive and negative bacteria. As nanotexture and Cu combine for dual methods of killing, this material should not contribute to drug-resistant bacteria as antibiotic use does. This approach involves applying a Cu coating on nanotextured stainless steel, resulting in an antibacterial activity within 30 min. Comprehensive characterization of the surface revealing that the Cu coating consists of metallic Cu and oxidized states (Cu2+ and Cu+), has been performed by this study. Cu-coated nSS induces a remarkable reduction of 97% in Gram-negative Escherichia coli and 99% Gram-positive Staphylococcus epidermidis bacteria. This material has potential to be used to create effective, scalable, and sustainable solutions to prevent bacterial infections caused by surface contamination without contributing to antibiotic resistance.

Advancing Antimicrobial Textiles: A Comprehensive Study on Combating ESKAPE Pathogens and Ensuring User Safety

Antibiotic-resistant bacteria, ESKAPE pathogens, present a significant and alarming threat to public health and healthcare systems. This study addresses the urgent need to combat antimicrobial resistance by exploring alternative ways to reduce the health and cost implications of infections caused by these pathogens. To disrupt their transmission, integrating antimicrobial textiles into personal protective equipment (PPE) is an encouraging avenue. Nevertheless, ensuring the effectiveness and safety of these textiles remains a persistent challenge. To achieve this, we conduct a comprehensive study that systematically compares the effectiveness and potential toxicity of five commonly used antimicrobial agents. To guide decision making, a MULTIMOORA method is employed to select and rank the optimal antimicrobial textile finishes. Through this approach, we determine that silver nitrate is the most suitable choice, while a methoxy-terminated quaternary ammonium compound is deemed less favorable in meeting the desired criteria. The findings of this study offer valuable insights and guidelines for the development of antimicrobial textiles that effectively address the requirements of effectiveness, safety, and durability. Implementing these research outcomes within the textile industry can significantly enhance protection against microbial infections, contribute to the improvement of public health, and mitigate the spread of infectious diseases.

Toxicity Mechanisms of Copper Nanoparticles and Copper Surfaces on Bacterial Cells and Viruses

Copper is a metal historically used to prevent infections. One of the most relevant challenges in modern society are infectious disease outbreaks, where copper-based technologies can play a significant role. Currently, copper nanoparticles and surfaces are the most common antimicrobial copper-based technologies. Despite the widespread use of copper on nanoparticles and surfaces, the toxicity mechanism(s) explaining their unique antimicrobial properties are not entirely known. In general, toxicity effects described in bacteria and fungi involve the rupture of membranes, accumulation of ions inside the cell, protein inactivation, and DNA damage. A few studies have associated Cu-toxicity with ROS production and genetic material degradation in viruses. Therefore, understanding the mechanisms of the toxicity of copper nanoparticles and surfaces will contribute to developing and implementing efficient antimicrobial technologies to combat old and new infectious agents that can lead to disease outbreaks such as COVID-19. This review summarizes the current knowledge regarding the microbial toxicity of copper nanoparticles and surfaces and the gaps in this knowledge. In addition, we discuss potential applications derived from discovering new elements of copper toxicity, such as using different molecules or modifications to potentiate toxicity or antimicrobial specificity.

A hybrid and scalable nanofabrication approach for bio-inspired bactericidal silicon nanospike surfaces

Insects and plants exhibit bactericidal properties through surface nanostructures, such as nanospikes, which physically kill bacteria without antibiotics or chemicals. This is a promising new avenue for achieving antibacterial surfaces. However, the existing methods for fabricating nanospikes are incapable of producing uniform nanostructures on a large scale and in a cost-effective manner. In this paper, a scalable nanofabrication method involving the application of nanosphere lithography and reactive ion etching for constructing nanospike surfaces is demonstrated. Low-cost silicon nanospikes with uniform spacing that were sized similarly to biological nanospikes on cicada wings with a 4-inch wafer scale were fabricated. The spacing, tip radius, and base diameter of the silicon nanospikes were controlled precisely by adjusting the nanosphere diameters, etching conditions, and diameter reduction. The bactericidal properties of the silicon nanospikes with 300 nm spacing were measured quantitatively using the standard viability plate count method; they killed E. coli cells with 59 % efficiency within 30 h. The antibacterial ability of the nanospike surface was further indicated by the morphological differences between bacteria observed in the scanning electron microscopic images as well as the live/dead stains of fluorescence signals. The fabrication process combined the advantages of both top-down and bottom-up methods and was a significant step toward affordable bio-inspired antibacterial surfaces.

Nanostructured Surfaces with Multimodal Antimicrobial Action

Self-disinfecting surfaces are a current pressing need for public health and safety in view of the current COVID-19 pandemic, where the keenly felt worldwide repercussions have highlighted the importance of infection control, frequent disinfection, and proper hygiene. Because of its potential impact upon real-world translation into downstream applications, there has been much research interest in multiple disciplines such as materials science, chemistry, biology, and engineering. Various antimicrobial technologies have been developed and currently applied on surfaces in public spaces, such as elevator buttons and escalator handrails. These technologies are mainly based on conventional methods of grafting quaternary ammonium salts (QACs) such as benzalkonium chloride or the immobilization of metal species of silver or copper. However, neither the long-term efficacy nor the fast-killing properties have been proven, and the future repercussions from extended use, such as environmental hazards and the induction of MDR development, is unknown. Nanostructured surfaces with excellent antimicrobial activities have been claimed to be the next generation of self-disinfecting surfaces with various promising applications and passive antimicrobial mechanisms, without the potential repercussions of active ingredient overuse. In this Account, we briefly introduce the concept of mechanobactericidal action realized by these nanostructured surfaces first discovered on cicada wings. The elimination of microbes on the surface was actualized by the physical rupture of the microbe cell wall by nanoprotusions, without any involvement of chemical species. By mimicking the physical features of naturally occurring biocidal surfaces, the fabrication of nanostructures on various substrates such as titania, silicon, and polymers has been well described. Observations of the dependence of their antimicrobial efficacy on physical characteristics such as height, density, and rigidity have also been documented. However, the complex fabrication of such nanostructures remains the main drawback preventing its widespread application. We outline our efforts in fabricating a series of zinc-based nanostructured materials with facile and generally applicable wet chemistry methods, including nanodaggered zeolitic imidazolate frameworks (ZIF-L) and ZnO nanoneedles. In our investigations, we discovered that there were additional modes of action that contributed to the excellent biocidal activities of our materials. The impact of surface chemistry and charge was partially responsible for the selectivity and efficacy of ZIF-L-coated surfaces, where the positively charged surfaces were able to attract and adhere negatively charged bacteria to the surface. The combination of semiconductor ZnO nanoneedles on electron-donating substrates allowed for the generation of reactive oxygen species (ROS), realizing the remote killing of bacteria unadhered to the nanostructured surface. Additionally, we demonstrate several real-life applications of the synthesized materials, underscoring the importance of materials development suited for scale-up and eventual translation to potential applications and commercial end products.

Copper hydroxide nanosheets-assembled nanofibrous membranes for anti-biofouling water disinfection

Copper hydroxide (Cu(OH)₂) has been elected as a newly-emerging green disinfectant to deal with membrane biofouling in the treatment of bacteria-contaminated water; however, the decoration strategy of it with the granular form on membrane substrates limits the practical application. Here a novel surface-confined methodology was proposed for preparing freestanding Cu(OH)₂ nanosheet-assembled nanofibrous membranes (CNNMs) with the anti-biofouling property via the in-suit coprecipitation and heat-induced growth method. The vertically aligned Cu(OH)₂ nanosheets were in-suit rooted on the surface of the nanofiber scaffold with high binding fastness. The acquired CNNMs possess comprehensive performances of high porosity, prominent mechanical strength, fatigue resistance, and superior bactericidal efficiency of 99.999%, which endowed the CNNMs ultrahigh filtration fluxes (24000 L m^-2 h^-1) and durability to disinfect bacteria-containing water effectively. This facile strategy may throw light on manufacturing novel inorganic nanosheet-rooted nanofibrous membranes for water disinfection and public health.