Synergetic Lipid Extraction with Oxidative Damage Amplifies Cell-Membrane-Destructive Stresses and Enables Rapid Sterilization

Photo-triggered AuAg@g-C3N4 composite nanoplatform for multimodal broad-spectrum antibacterial therapy

Strategies based on nanomaterials for sterilization address the problem of antibiotic resistance faced by conventional antimicrobials, with the contribution of photocatalytic compounds being particularly prominent. Herein, to integrate multiple bactericidal techniques into a system for generating synergistic antibacterial effects, a novel photo-triggered AuAg@g-C3N4 composite nanoplatform was constructed by anchoring AuAg on the surface of a g-C3N4 layer. As the composite nanoplatform had a lower bandgap and superior visible light utilization efficiency, it could facilitate free electron transfer better and exhibit superior photocatalytic activity under light conditions. Moreover, the AuAg@g-C3N4 composite nanoplatform integrated the bactericidal modes of silver ion toxicity, physical disruption of bacterial cell membranes by the multilayer structure, and excellent photocatalytic activity, exhibiting extremely superior bactericidal effects against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Bacillus subtilis, with a bactericidal efficiency of up to 100%.

Coagulation/co-catalytic membrane integrated system for fouling-resistant and efficient water purification

Low-pressure catalytic membranes allow efficient rejection of particulates and simultaneously removing organics pollutant in water, but the accumulation of dissolved organic matters (DOM) on membrane surface, which cover the catalytic sites and cause membrane fouling, challenges their stable operation in practical wastewater treatment. Here we propose a ferric salt-based coagulation/co-catalytic membrane integrated system that can effectively mitigate the detrimental effects of DOM. Ferric salt (Fe3+) serving both as a DOM coagulant to lower the membrane fouling and as a co-catalyst with the membrane-embedded MoS2 nanosheets to drive perxymonosulfate (PMS) activation and pollutant degradation. The membrane functionalized with 2H-phased MoS2 nanosheets showed improved hydrophilicity and fouling resistance relative to the blank polysulfone membrane. Attributed to the DOM coagulation and co-catalytic generation of surface-bound radicals for decontamination at membrane surface, the catalytic membrane/PMS/ Fe3+ system showed much less membrane fouling and 2.6 times higher pollutant degradation rate in wastewater treatment than the catalytic membrane alone. Our work imply a great potential of coagulation/co-catalytic membrane integrated system for water purification application.

Unveiling the antibacterial strategies and mechanisms of MoS2: a comprehensive analysis and future directions

Antibiotic resistance is a growing problem that requires alternative antibacterial agents. MoS2, a two-dimensional transition metal sulfide, has gained significant attention in recent years due to its exceptional photocatalytic performance, excellent infrared photothermal effect, and impressive antibacterial properties. This review presents a detailed analysis of the antibacterial strategies and mechanism of MoS2, starting with its morphology and synthesis methods and focusing on the different interaction stages between MoS2 and bacteria. The paper summarizes the main antibacterial mechanisms of MoS2, such as photocatalytic antibacterial, enzyme-like catalytic antibacterial, physical antibacterial, and photothermal-assisted antibacterial. It offers a comprehensive discussion focus on recent research studies of photocatalytic antibacterial mechanisms and categorizes them, guiding the application of MoS2 in the antibacterial field. Overall, the review provides an in-depth understanding of the antibacterial mechanisms of MoS2 and presents the challenges and future directions for the improvement of MoS2 in the field of high-efficiency antibacterial materials.

Nanomaterials-Enabled Physicochemical Antibacterial Therapeutics: Toward the Antibiotic-Free Disinfections

Bacterial infection continues to be an increasing global health problem with the most widely accepted treatment paradigms restricted to antibiotics. However, the overuse and misuse of antibiotics have triggered multidrug resistance of bacteria, frustrating therapeutic outcomes, and leading to higher mortality rates. Even worse, the tendency of bacteria to form biofilms on living and nonliving surfaces further increases the difficulty in confronting bacteria because the extracellular matrix can act as a robust barrier to prevent the penetration of antibiotics and resist environmental damage. As a result, the inability to eliminate bacteria and biofilms often leads to persistent infection, implant failure, and device damage. Therefore, it is of paramount importance to develop alternative antimicrobial agents while avoiding the generation of bacterial resistance to prevent the large-scale growth of bacterial resistance. In recent years, nano-antibacterial materials have played a vital role in the antibacterial field because of their excellent physical and chemical properties. This review focuses on new physicochemical antibacterial strategies and versatile antibacterial nanomaterials, especially the mechanism and types of 2D antibacterial nanomaterials. In addition, this advanced review provides guidance on the development direction of antibiotic-free disinfections in the antibacterial field in the future.

Hydrodynamic tearing of bacteria on nanotips for sustainable water disinfection

Water disinfection is conventionally achieved by oxidation or irradiation, which is often associated with a high carbon footprint and the formation of toxic byproducts. Here, we describe a nano-structured material that is highly effective at killing bacteria in water through a hydrodynamic mechanism. The material consists of carbon-coated, sharp Cu(OH)2 nanowires grown on a copper foam substrate. We show that mild water flow (e.g. driven from a storage tank) can efficiently tear up bacteria through a high dispersion force between the nanotip surface and the cell envelope. Bacterial cell rupture is due to tearing of the cell envelope rather than collisions. This mechanism produces rapid inactivation of bacteria in water, and achieved complete disinfection in a 30-day field test. Our approach exploits fluidic energy and does not require additional energy supply, thus offering an efficient and low-cost system that could potentially be incorporated in water treatment processes in wastewater facilities and rural communities.

Photo-sterilization of groundwater by tellurium and enhancement by micro/nano bubbles

In rural areas where low-temperature groundwater is used as a drinking water source, cost-effective sterilization techniques are needed to prevent groundwater consumers from the disease risks triggered by pathogenic microorganisms like Escherichia coli and fungal spores. In this study, micro/nano bubbles (MNBs) coupled with the tellurium (Te)-based catalysts were used to considerably enhance the solar disinfection (SODIS) efficiency while overcoming the intrinsic defects of SODIS, particularly in low-temperature. Sterilization tests showed that 6.5 log₁₀ cfu/mL of E. coli K-12 and 4.0 log₁₀ cfu/mL of Aspergillus niger spores were completely inactivated within 5 min while applying this novel process for disinfection of raw groundwater, even in low-temperature. The underlying mechanisms of the extraordinary sterilization efficiency were revealed through comprehensive characterization of the catalysts and the physiological changes of the microorganisms. The localized surface plasmon resonance (LSPR) effect of the Te catalysts was identified to take advantage of photothermal synergism to achieve cell death. The integration of MNBs with the facet-engineered Te catalysts improved the photothermal catalytic effect and extracellular electron transfer, which substantially strengthened disinfection efficiency. This study provides a targeted solution into microbial inactivation in groundwater and emphasizes a cost-effective groundwater sterilization process.

Oxygen vacancy mediated α-MoO3 bactericidal nanocatalyst in the dark: Surface structure dependent superoxide generation and antibacterial mechanisms

Understanding bacteria inactivation mechanisms of nanomaterials on the surface molecular level is of prime importance for the development of antibacterial materials and their application in restraining the transmission of pathogenic microorganisms. This study prepared an oxygen vacancy-mediated bactericidal nanocatalyst α-MoO₃ which exhibited excellent antibacterial activity against Escherichia coli and Staphylococcus aureus in the dark. By manipulating the surface structure of α-MoO₃, the facile tuning of superoxide radical (•O₂^-) generation can be achieved, which was confirmed by electron paramagnetic resonance. •O₂^- disrupted bacterial membrane through attacking lipopolysaccharide (LPS) and phosphatidylethanolamine (PE). Intracellular reactive oxygen species (ROS) experiments confirm that oxidative stress induced by •O₂^- also played a vital role in bacterial inactivation, which might account for DNA damage verified by comet assays. The α-MoO₃ with rich oxygen vacancies also exhibited good antibacterial efficiency (＞99.00 %) toward airborne microbes under dark conditions, indicating its potential to impede the transmission of pathogenic microbes.

Work function mediated interface charge kinetics for boosting photocatalytic water sterilization

Photocatalytic sterilization is an eco-friendly strategy to utilize solar energy for treating water contaminated with resistant bacteria. Here, we propose interface engineering to induce an internal electric field (IEF) in leaf-like Ti₃C₂Tx/TiO₂ based on the work function (Φ) theory, which enhances photocatalytic sterilization performance by steering interface charge kinetics. Density functional theory (DFT) calculations and in situ irradiation X-ray photoelectron spectroscopy (ISI-XPS) results show that photogenerated charge carriers can be directionally separated by the IEF. The efficient charge kinetics benefits the reactive oxygen species (ROS) generation and hence a superior broad-spectrum sterilization performance. We employ the intrinsic physical characteristics of MXene to steer interface charge kinetics for photocatalysis, which exhibits great potential in water disinfection.

Interaction of Graphitic Carbon Nitride with Cell Membranes: Probing Phospholipid Extraction and Lipid Bilayer Destruction

Understanding how nanomaterials interact with cell membranes has important implications for ecotoxicology and human health. Here, we investigated the interactions between graphitic carbon nitride (g-C₃N₄, CN) and red blood cells, a plausible contact target for nanoparticles when they enter the bloodstream. Through a hemolysis assay, the cytotoxicity of CN derived from different precursors was quantitatively assessed, which is highly related to the surface area of CN. Reactive oxygen species (ROS) generation and lipid peroxidation detection confirmed that CN causes rapid cell membrane rupture by a physical interaction mechanism rather than ROS-related chemical oxidation. Dye leakage assay and theoretical simulation indicated that the less-layered CN is prone to folding inward to wrap and extract lipid molecules from cell membranes. The electron-rich inherent pores of CN play a dominant role in capturing the headgroups of phospholipids, whereas the hydrophobic interaction is critical for the anchoring of lipid tails. Our further experimental evidence demonstrated that the destructive extraction of phospholipids from cell membranes by CN occurs primarily in the outer leaflet, and phosphatidylcholine is the most easily extracted lipid. Moreover, the formation of protein corona on CN was found to decrease the nonspecific interactions but increase steric repulsion, thus mitigating CN cytotoxicity. Overall, our data provide a molecular basis for CN's cytotoxicity.

2D Molybdenum Sulfide-Based Materials for Photo-Excited Antibacterial Application

Bacterial infections have seriously threatened human health and the abuse of natural or artificial antibiotics leads to bacterial resistance, so development of a new generation of antibacterial agents and treatment methods is urgent. 2D molybdenum sulfide (MoS₂ ) has good biocompatibility, high specific surface area to facilitate surface modification and drug loading, adjustable energy bandgap, and high near-infrared photothermal conversion efficiency (PCE), so it is often used for antibacterial application through its photothermal or photodynamic effects. This review comprehensively summarizes and discusses the fabrication processes, structural characteristics, antibacterial performance, and the corresponding mechanisms of MoS₂ -based materials as well as their representative antibacterial applications. In addition, the outlooks on the remaining challenges that should be addressed in the field of MoS₂ are also proposed.

Catalyst-Free Periodate Activation by Solar Irradiation for Bacterial Disinfection: Performance and Mechanisms

Periodate (PI)-based advanced oxidation process has recently attracted great attention in the water treatment processes. In this study, solar irradiation was used for PI activation to disinfect waterborne bacteria. The PI/solar irradiation system could inactivate Escherichia coli below the limit of detection (LOD, 10 CFU mL^-1) with initial concentrations of 1 × 10⁶, 1 × 10⁷, and 1 × 10⁸ CFU mL^-1 within 20, 40, and 100 min, respectively. ^•O₂^- and ^•OH radicals contributed to the bacterial disinfection. These reactive radicals could attack and penetrate the cell membrane, thereby increasing the amount of intracellular reactive oxygen species and destroying the intracellular defense system. The damage of the cell membrane caused the leakage of intracellular K⁺ and DNA (that could be eventually degraded). Excellent bacterial disinfection performance in PI/solar irradiation systems was achieved in a wide range of solution pH (3-9), with coexisting humic acid (0.1-10 mg L^-1) and broad solution ionic strengths (15-600 mM). The PI/solar irradiation system could also efficiently inactivate Gram-positive Bacillus subtilis. Moreover, PI activated by natural sunlight irradiation could inactivate 1 × 10⁷ CFU mL^-1 viable E. coli below the LOD in the river and sea waters with a working volume of 1 L in 40 and 50 min, respectively. Clearly, the PI/solar system could be potentially applied to disinfect bacteria in water.

Incorporating Boron into Niobic Acid Nanosheets Enables Generation of Multiple Reactive Oxygen Species for Superior Antibacterial Action

Photocatalytic therapy is an alternative antibacterial pathway but most photocatalysts are limited by light absorption, charge transfer and insufficient production of reactive oxygen species (ROS). Herein, the authors utilize boron doped niobic acid nanosheets (B-HNbO₃ NSs) as a superior photocatalytic antibacterial platform. The experimental results and density functional theory (DFT) confirm that superior photocatalytic therapy activity is mainly due to boron doping, which not only promotes the generation and separation of electrons and holes, but also enhances the adsorption of water and oxygen molecules on B-HNbO₃ NSs. Consequently, multiple ROS including hydroxyl radicals (•OH), superoxide radicals (•O₂^- ), and singlet oxygen (¹ O₂ ) are generated under light irradiation, resulting in outstanding bacterial killing ability of B-HNbO₃ NSs. Besides, oxygen is produced during the therapy process, thus alleviating the inflammatory response caused by hypoxia. Furthermore, molecular dynamics (MD) simulations verify that the nanosheet structure makes it possess strong electrostatic attraction for bacterial cell membranes, leading to physical insertion and damage to bacterial cells. Therefore, bactericidal rates for four types of bacteria are all more than 99%, proving its excellent and broad-spectrum antibacterial capacity. Moreover, B-HNbO₃ NSs could be applied to treat biofilm-coated medical devices in vivo, suggesting its possibility in practical application.

Layered double hydroxide based materials applied in persulfate based advanced oxidation processes: Property, mechanism, application and perspectives

Recently, persulfate-based advanced oxidation processes (persulfate-AOPs) are booming rapidly due to their promising potential in treating refractory contaminants. As a type of popular two-dimensional material, layered double hydroxides (LDHs) are widely used in energy conversion, medicine, environment remediation and other fields for the advantages of high specific surface area (SSA), good tunability, biocompatibility and facile fabrication. These excellent physicochemical characteristics may enable LDH-based materials to be promising catalysts in persulfate-AOPs. In this work, we make a summary of LDHs and their composites in persulfate-AOPs from different aspects. Firstly, we introduce different structure and important properties of LDH-based materials briefly. Secondly, various LDH-based materials are classified according to the type of foreign materials (metal or carbonaceous materials, mainly). Latterly, we discuss the mechanisms of persulfate activation (including radical pathway and nonradical pathway) by these catalysts in detail, which involve (i) bimetallic synergism for radical generation, (ii) the role of carbonaceous materials in radical generation, (iii) singlet oxygen (¹O₂) production and several special nonradical mechanisms. In addition, the catalytic performance of LDH-based catalysts for contaminants are also summarized. Finally, challenges and future prospects of LDH-based composites in environmental remediation are proposed. We expect this review could bring new insights for the development of LDH-based catalyst and exploration of reaction mechanism.

Inactivation of Microcystis Aeruginosa by peracetic acid combined with ultraviolet: Performance and characteristics

The inactivation of algae by a combined process of peracetic acid and ultraviolet irradiation (UV/PAA) was systematically investigated by choosing Microcystis aeruginosa as the reference algal species. Both hydroxyl (HO^•) and organic radicals (RO^•) contributed to the cell integrity loss and RO^• played the dominant roles. The algae inactivation kinetics can be well fitted by the typical Hom model, showing that the inactivation kinetic curves followed a type of shoulder and exponential reduction. The initial shoulder might be induced by the protection from the cell wall. Although the results from the cell morphology, UV-vis spectra and fluorescence excitation-emission matrices analysis suggested the cell lysis and the release of algal organic matter (AOM) in the UV/PAA process, the AOM could be subsequently degraded. Humic acid (1 - 5 mg/L) inhibited the algal cell inactivation, and the presence of chloride (0.5 - 2 mM) had little effect on the cell viability reduction. However, the addition of bicarbonate (1 - 5 mM) promoted cell integrity loss. The UV/PAA process displayed better performance under the natural water background, demonstrating the extensive potential for the practical application of this approach. This study suggests that the UV/PAA process is an effective strategy for algae inactivation.

Risks, characteristics, and control strategies of disinfection-residual-bacteria (DRB) from the perspective of microbial community structure

The epidemic of COVID-19 has aroused people's particular attention to biosafety. A growing number of disinfection products have been consumed during this period. However, the flaw of disinfection has not received enough attention, especially in water treatment processes. While cutting down the quantity of microorganisms, disinfection processes exert a considerable selection effect on bacteria and thus reshape the microbial community structure to a great extent, causing the problem of disinfection-residual-bacteria (DRB). These systematic and profound changes could lead to the shift in regrowth potential, bio fouling potential, as well as antibiotic resistance level and might cause a series of potential risks. In this review, we collected and summarized the data from the literature in recent 10 years about the microbial community structure shifting of natural water or wastewater in full-scale treatment plants caused by disinfection. Based on these data, typical DRB with the most reporting frequency after disinfection by chlorine-containing disinfectants, ozone disinfection, and ultraviolet disinfection were identified and summarized, which were the bacteria with a relative abundance of over 5% in the residual bacteria community and the bacteria with an increasing rate of relative abundance over 100% after disinfection. Furthermore, the phylogenic relationship and potential risks of these typical DRB were also analyzed. Twelve out of fifteen typical DRB genera contain pathogenic strains, and many were reported of great secretion ability. Pseudomonas and Acinetobacter possess multiple disinfection resistance and could be considered as model bacteria in future studies of disinfection. We also discussed the growth, secretion, and antibiotic resistance characteristics of DRB, as well as possible control strategies. The DRB phenomenon is not limited to water treatment but also exists in the air and solid disinfection processes, which need more attention and more profound research, especially in the period of COVID-19.