A Hierarchical 3D Nanostructured Microfluidic Device for Sensitive Detection of Pathogenic Bacteria

Efficient capture and rapid detection of pathogenic bacteria from body fluids lead to early diagnostics of bacterial infections and significantly enhance the survival rate. We propose a universal nano/microfluidic device integrated with a 3D nanostructured detection platform for sensitive and quantifiable detection of pathogenic bacteria. Surface characterization of the nanostructured detection platform confirms a uniform distribution of hierarchical 3D nano‐/microisland (NMI) structures with spatial orientation and nanorough protrusions. The hierarchical 3D NMI is the unique characteristic of the integrated device, which enables enhanced capture and quantifiable detection of bacteria via both a probe‐free and immunoaffinity detection method. As a proof of principle, we demonstrate probe‐free capture of pathogenic Escherichia coli (E. coli) and immunocapture of methicillin‐resistant‐Staphylococcus aureus (MRSA). Our device demonstrates a linear range between 50 and 10⁴ CFU mL^?1, with average efficiency of 93% and 85% for probe‐free detection of E. coli and immunoaffinity detection of MRSA, respectively. It is successfully demonstrated that the spatial orientation of 3D NMIs contributes in quantifiable detection of fluorescently labeled bacteria, while the nanorough protrusions contribute in probe‐free capture of bacteria. The ease of fabrication, integration, and implementation can inspire future point‐of‐care devices based on nanomaterial interfaces for sensitive and high‐throughput optical detection.     

Broad‐Spectrum Antibacterial Activity of Carbon Nanotubes to Human Gut Bacteria

Carbon nanotubes (CNTs) hold promise in manufacturing, environmental, and biomedical applications, as well as food and agricultural industries. Previous observations have shown that CNTs have antimicrobial activity; however, the impact of CNTs to human gut microbes has not been investigated. Here, the antibacterial activity of CNTs against the microbes commonly encountered in the human digestion system—L. acidophilus, B. adolescentis, E. coli, E. faecalis, and S. aureus—are evaluated. The bacteria studied include pathogenic and non‐pathogenic, gram‐positive and negative, and both sphere and rod strains. In this study, CNTs, including single‐walled CNTs (SWCNTs, 1–3 μm), short and long multi‐walled CNTs (s‐MWCNTs: 0.5–2 μm; l‐MWCNTs: >50 μm), and functionalized multi‐walled CNTs (hydroxyl‐ and carboxyl‐modification, 0.5–2 μm), all have broad‐spectrum antibacterial effects. Notably, CNTs may selectively lyse the walls and membranes of human gut microbes, depending on not only the length and surface functional groups of CNTs, but also the shapes of the bacteria. The mechanism of antibacterial activity is associated with their diameter‐dependent piercing and length‐dependent wrapping on the lysis of microbial walls and membranes, inducing release of intracellular components DNA and RNA and allowing a loss of bacterial membrane potential, demonstrating complete destruction of bacteria. Thin and rigid SWCNT show more effective wall/membrane piercing on spherical bacteria than MWCNTs. Long MWCNT may wrap around gut bacteria, increasing the area making contact with the bacterial wall. This work suggests that CNTs may be broad‐spectrum and efficient antibacterial agents in the gut, and selective application of CNTs could reduce the potential hazard to probiotic bacteria.     

Construction of Single‐Iron‐Atom Nanocatalysts for Highly Efficient Catalytic Antibiotics

Bacterial infection caused by pathogenic bacteria has long been an intractable issue that threatens human health. Herein, the fact that nanocatalysts with single iron atoms anchored in nitrogen‐doped amorphous carbon (SAF NCs) can effectively induce peroxidase‐like activities in the presence of H₂O₂, generating abundant hydroxyl radicals for highly effective bacterial elimination (e.g., Escherichia coli and Staphylococcus aureus), is reported. In combination with the intrinsic photothermal performance of the nanocatalysts, noticeable bacterial‐killing effects are extensively investigated. Especially, the antibacterial mechanism of critical cell membrane destruction induced by SAF NCs is unveiled. Based on the bactericidal properties of SAF NCs, in vivo bacterial infections propagated at wounds by E. coli and S. aureus pathogens can be effectively eradicated, resulting in better wound healing. Collectively, the present study highlights the highly efficient in vitro antibacterial and in vivo anti‐infection performances by the single‐iron‐atom‐containing nanocatalysts.     

Chitosan–silver oxide nanocomposite film: Preparation and antimicrobial activity

The chitosan–silver oxide encapsulated nanocomposite film was prepared by solution casting method. The prepared film was characterized by FTIR, scanning electron microscopy (SEM), thermal studies, and UV-Vis spectroscopy. The elemental composition of the film was studied by energy dispersive X-ray analysis (EDAX). The antibacterial activity of the composite film against pathogenic bacteria viz. Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Pseudomonas aeruginosa was measured by agar diffusion method. Our observations suggest that chitosan as biomaterial based nanocomposite film containing silver oxide has an excellent antibacterial ability for food packaging applications.     

In Vivo Dynamic Monitoring of Bacterial Infection by NIR‐II Fluorescence Imaging

Time window of antibiotic administration is a critical but long‐neglected point in the treatment of bacterial infection, as unnecessary prolonged antibiotics are increasingly causing catastrophic drug‐resistance. Here, a second near‐infrared (NIR‐II) fluorescence imaging strategy based on lead sulfide quantum dots (PbS QDs) is presented to dynamically monitor bacterial infection in vivo in a real‐time manner. The prepared PbS QDs not only provide a low detection limit (10⁴ CFU mL^?1) of four typical bacteria strains in vitro but also show a particularly high labeling efficiency with Escherichia coli (E. coli). The NIR‐II in vivo imaging results reveal that the number of invading bacteria first decreases after post‐injection, then increases from 1 d to 1 week and drop again over time in infected mouse models. Meanwhile, there is a simultaneous variation of dendritic cells, neutrophils, macrophages, and CD8+ T lymphocytes against bacterial infection at the same time points. Notably, the infected mouse self‐heals eventually without antibiotic treatment, as a robust immune system can successfully prevent further health deterioration. The NIR‐II imaging approach enables real‐time monitoring of bacterial infection in vivo, thus facilitating spatiotemporal deciphering of time window for antibiotic treatment.     

In Situ Fabrication of Ultrasmall Gold Nanoparticles/2D MOFs Hybrid as Nanozyme for Antibacterial Therapy

As one of the common reactive oxygen species, H₂O₂ has been widely used for combating pathogenic bacterial infections. However, the high dosage of H₂O₂ can induce undesired damages to normal tissues and delay wound healing. In this regard, peroxidase‐like nanomaterials serve as promising nanozymes, thanks to their positive promotion toward the antibacterial performance of H₂O₂, while avoiding the toxicity caused by the high concentrations of H₂O₂. In this work, ultrasmall Au nanoparticles (UsAuNPs) are grown on ultrathin 2D metal–organic frameworks (MOFs) via in situ reduction. The formed UsAuNPs/MOFs hybrid features both the advantages of UsAuNPs and ultrathin 2D MOFs, displaying a remarkable peroxidase‐like activity toward H₂O₂ decomposition into toxic hydroxyl radicals (·OH). Results show that the as‐prepared UsAuNPs/MOFs nanozyme exhibits excellent antibacterial properties against both Gram‐negative (Escherichia coli) and Gram‐positive (Staphylococcus aureus) bacteria with the assistance of a low dosage of H₂O₂. Animal experiments indicate that this hybrid material can effectively facilitate wound healing with good biocompatibility. This study reveals the promising potential of a hybrid nanozyme for antibacterial therapy and holds great promise for future clinical applications.     

3D Porous Hydrogel/Conducting Polymer Heterogeneous Membranes with Electro‐/pH‐Modulated Ionic Rectification

Heterogeneous membranes composed of asymmetric structures or compositions have enormous potential in sensors, molecular sieves, and energy devices due to their unique ion transport properties such as ionic current rectification and ion selectivity. So far, heterogeneous membranes with 1D nanopores have been extensively studied. However, asymmetric structures with 3D micro‐/nanoscale pore networks have never been investigated. Here, a simple and versatile approach to low‐costly fabricate hydrogel/conducting polymer asymmetric heterogeneous membranes with electro‐/pH‐responsive 3D micro‐/nanoscale ion channels is introduced. Due to the asymmetric heterojunctions between positively charged nanoporous polypyrrole (PPy) and negatively charged microscale porous hydrogel poly (acrylamide‐co‐acrylic acid) (P(AAm‐co‐AA)), the membrane can rectify ion transmembrane transport in response to both electro‐ and pH‐stimuli. Numerical simulations based on coupled Poisson and Nernst–Plank equations are carried out to explain the ionic rectification mechanisms for the membranes. The membranes are not dependent on elaborately fabricated 1D ion channel substrates and hence can be facilely prepared in a low‐cost and large‐area way. The hybridization of hydrogel and conducting polymer offers a novel strategy for constructing low‐cost, large‐area and multifunctional membranes, expanding the tunable ionic rectification properties into macroscopic membranes with micro‐/nanoscale pores, which would stimulate practical applications of the membranes.     

Coculture with Low‐Dose SWCNT Attenuates Bacterial Invasion and Inflammation in Human Enterocyte‐like Caco‐2 Cells

Single walled carbon nanotubes (SWCNTs) have been shown to be highly effective against a wide range of bacteria. Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) infection is a well‐known mediator to prolong hospitalization and initiate chronic inflammation, yet the biological effects of SWCNTs on the pathogen‐infected enterocytes remain unclear. Herein, it is shown that the low‐dose SWCNT treatment attenuates the human enterocyte‐like Caco‐2 cells from the damage of E. coli and S. aureus infection by suppressing NLRP3 inflammasome activation. The relatively low‐dose (1 and 10 μg mL^?1) SWCNT treatments reduce the adhesion and invasion of E. coli and S. aureus to Caco‐2 cells, increase the cell viability and proliferation, reduce the tight junction permeability, and restitute the integrity of cell surface microvilli structure, meanwhile has low cytotoxicity to the host cells. The low‐dose SWCNT treatment further reduces the NLRP3‐mediated IL‐1β secretion in the infected cells. The results identify that a low‐dose SWCNT treatment serves a protective function for the E. coli‐ and S. aureus‐infected Caco‐2 cells by negatively regulating mitochondrial reactive oxygen species‐mediated NLRP3 inflammasome activation.     

Green Fabrication of Amphiphilic Quaternized β‐Chitin Derivatives with Excellent Biocompatibility and Antibacterial Activities for Wound Healing

Bacterial infection has always been a great threat to public health, and new antimicrobials to combat it are urgently needed. Here, a series of quaternized β‐chitin derivatives is prepared simply and homogeneously in an aqueous KOH/urea solution, which is a high‐efficiency, energy‐saving, and “green” route for the modification of chitin. The mild reaction conditions keep the acetamido groups of β‐chitin intact and introduce quaternary ammonium groups on the primary hydroxyl at the C‐6 position of the chitin backbone, allowing the quaternized β‐chitin derivatives (QCs) to easily form micelles. These QCs are found to exhibit excellent antimicrobial activities against Escherichia coli, Staphylococcus aureus, Candida albicans, and Rhizopus oryzae with minimum inhibitory concentrations (MICs) of 8, 12, 60, and 40 µg mL^?1, respectively. As a specific highlight, their inherent outstanding biocompatibility and significant accelerating effects on the healing of uninfected, E. coli‐infected, and S. aureus‐infected wounds imply that these novel polysaccharide‐based materials can be used as dressings for clinical skin regeneration, particularly for infected wounds.     

Vacuum effect on DNA lesion and genetic mutation of cells

DNA topological forms can be changed by environmental factors thus to potentially cause genetic mutation. Vacuum of low pressure is considered to be such a factor. An investigation was carried out to check topological form changes of extracellular plasmid DNA due to lesion in DNA under the vacuum condition. Pumping the experimental stage of biological samples to vacuum may result in three effects on the environment of the sample, namely, low pressure, low temperature and low humidity, all of which may impact DNA. In the experiment, the DNA topological form change and related lesion after plasmid DNA samples were exposed to vacuum with varied time was analyzed with gel electrophoresis and fluorometric assay. The electrophoresis results were quantified to obtain percentages of the supercoiled and relaxed forms but no linear form of DNA. The fluorometer measured concentrations of single strand and double strand DNAs. The results showed that the single strand break was the dominant lesion in DNA. The DNA form change and the lesion were found to depend mainly on the pressure change but not much on the pressure itself. The vacuum-exposed DNA was subsequently transformed into bacteria Escherichia coli (E. coli) for checking mutation occurrence. No observable mutation of the DNA-transformed bacteria was found. This study concluded that certain light lesion in DNA dominated by the single strand break could be induced by vacuum exposure but with negligible risk of genetic mutation.     

Continuous Production of Discrete Plasmid DNA‐Polycation Nanoparticles Using Flash Nanocomplexation

Despite successful demonstration of linear polyethyleneimine (lPEI) as an effective carrier for a wide range of gene medicine, including DNA plasmids, small interfering RNAs, mRNAs, etc., and continuous improvement of the physical properties and biological performance of the polyelectrolyte complex nanoparticles prepared from lPEI and nucleic acids, there still exist major challenges to produce these nanocomplexes in a scalable manner, particularly for lPEI/DNA nanoparticles. This has significantly hindered the progress toward clinical translation of these nanoparticle‐based gene medicine. Here the authors report a flash nanocomplexation (FNC) method that achieves continuous production of lPEI/plasmid DNA nanoparticles with narrow size distribution using a confined impinging jet device. The method involves the complex coacervation of negatively charged DNA plasmid and positive charged lPEI under rapid, highly dynamic, and homogeneous mixing conditions, producing polyelectrolyte complex nanoparticles with narrow distribution of particle size and shape. The average number of plasmid DNA packaged per nanoparticles and its distribution are similar between the FNC method and the small‐scale batch mixing method. In addition, the nanoparticles prepared by these two methods exhibit similar cell transfection efficiency. These results confirm that FNC is an effective and scalable method that can produce well‐controlled lPEI/plasmid DNA nanoparticles.     

Photoluminenscence Blinking Dynamics of Colloidal Quantum Dots in the Presence of Controlled External Electron Traps

The effect of the external charge trap on the photoluminescence blinking dynamics of individual colloidal quantum dots is investigated with a series of colloidal quantum dot–bridge–fullerene dimers with varying bridge lengths, where the fullerene moiety acts as a well‐defined, well‐positioned external charge trap. It is found that charge transfer followed by charge recombination is an important mechanism in determining the blinking behavior of quantum dots when the external trap is properly coupled with the excited state of the quantum dot, leading to a quasi‐continuous distribution of ‘on' states and an early fall‐off from a power‐law distribution for both ‘on' and ‘off' times associated with quantum dot photoluminescence blinking.     

Colorimetric Detection of Escherichia coli Based on the Enzyme‐Induced Metallization of Gold Nanorods

A novel enzyme‐induced metallization colorimetric assay is developed to monitor and measure beta‐galactosidase (β‐gal) activity, and is further employed for colorimetric bacteriophage (phage)‐enabled detection of Escherichia coli (E. coli). This assay relies on enzymatic reaction‐induced silver deposition on the surface of gold nanorods (AuNRs). In the presence of β‐gal, the substrate p‐aminophenyl β‐d ‐galactopyranoside is hydrolyzed to produce p‐aminophenol (PAP). Reduction of silver ions by PAP generates a silver shell on the surface of AuNRs, resulting in the blue shift of the longitudinal localized surface plasmon resonance peak and multicolor changes of the detection solution from light green to orange‐red. Under optimized conditions, the detection limit for β‐gal is 128 pM, which is lower than the conventional colorimetric assay. Additionally, the assay has a broader dynamic range for β‐gal detection. The specificity of this assay for the detection of β‐gal is demonstrated against several protein competitors. Additionally, this technique is successfully applied to detect E. coli bacteria cells in combination with bacteriophage infection. Due to the simplicity and short incubation time of this enzyme‐induced metallization colorimetric method, the assay is well suited for the detection of bacteria in low‐resource settings.     

Electrophoretic Deposited Stable Chitosan@MoS2 Coating with Rapid In Situ Bacteria‐Killing Ability under Dual‐Light Irradiation

Developing in situ disinfection methods in vivo to avoid drug‐resistant bacteria and tissue toxicity is an urgent need. Here, the photodynamic and photothermal properties of the chitosan‐assisted MoS₂ (CS@MoS₂) hybrid coating are simultaneously inspired to endow metallic Ti implants with excellent surface self‐antibacterial capabilities. This coating, irradiated by only 660 nm visible light (VL) for 10 min, exhibits an antibacterial efficacy of 91.58% and 92.52% against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), respectively. The corresponding value is 64.67% and 57.44%, respectively, after irradiation by a single 808 nm near infrared light for the same amount of time. However, the combined irradiation using both lights can significantly enhance the efficiency up to 99.84% and 99.65% against E. coli and S. aureus, respectively, which can be ascribed to the synergistic effects of photodynamic and photothermal actions. The former produces single oxygen species under 660 nm VL while the latter induces a rise in temperature of implants, which can inhibit the growth of both E. coli and S. aureus. The introduction of CS can also promote the biocompatibility of implants, which provides a facile, rapid, and safe in situ bacteria‐killing method in vivo without needing a second surgery.     

A Chain‐Elongated Oligophenylenevinylene Electrolyte Increases Microbial Membrane Stability

A novel conjugated oligoelectrolyte (COE) material, named S6 , is designed to have a lipid‐bilayer stabilizing topology afforded by an extended oligophenylenevinylene backbone. S6 intercalates biological membranes acting as a hydrophobic support for glycerophospholipid acyl chains. Indeed, Escherichia coli treated with S6 exhibits a twofold improvement in butanol tolerance, a relevant feature to achieve within the general context of modifying microorganisms used in biofuel production. Filamentous growth, a morphological stress response to butanol toxicity in E. coli, is observed in untreated cells after incubation with 0.9% butanol (v/v), but is mitigated by S6 treatment. Real‐time fluorescence imaging using giant unilamellar vesicles reveals the extent to which S6 counters membrane instability. Moreover, S6 also reduces butanol‐induced lipopolysaccharide release from the outer membrane to further maintain cell integrity. These findings highlight a deliberate effort in the molecular design of a chain‐elongated COE to stabilize microbial membranes against environmental challenges.     

Rapid and Superior Bacteria Killing of Carbon Quantum Dots/ZnO Decorated Injectable Folic Acid‐Conjugated PDA Hydrogel through Dual‐Light Triggered ROS and Membrane Permeability

One of the most difficult challenges in the biomedical field is bacterial infection, which causes tremendous harm to human health. In this work, an injectable hydrogel is synthesized through rapid assembly of dopamine (DA) and folic acid (FA) cross‐linked by transition metal ions (TMIs, i.e., Zn²⁺), which was named as DFT‐hydrogel. Both the two carboxyl groups in the FA molecule and catechol in polydopamine (PDA) easily chelates Zn²⁺ to form metal–ligand coordination, thereby allowing this injectable hydrogel to match the shapes of wounds. In addition, PDA in the hydrogel coated around carbon quantum dot‐decorated ZnO (C/ZnO) nanoparticles (NPs) to rapidly generate reactive oxygen species (ROS) and heat under illumination with 660 and 808 nm light, endows this hybrid hydrogel with great antibacterial efficacy against Staphylococcus aureus (S. aureus, typical Gram‐positive bacteria) and Escherichia coli (E. coli, typical Gram‐negative bacteria). The antibacterial efficacy of the prepared DFT‐C/ZnO‐hydrogel against S. aureus and E. coli under dual‐light irradiation is 99.9%. Importantly, the hydrogels release zinc ions over 12 days, resulting in a sustained antimicrobial effect and promoted fibroblast growth. Thus, this hybrid hydrogel exhibits great potential for the reconstruction of bacteria‐infected tissues, especially exposed wounds.     

Synthesis of Bimetallic Conductive 2D Metal–Organic Framework (CoxNiy‐CAT) and Its Mass Production: Enhanced Electrochemical Oxygen Reduction Activity

The development of new electrocatalysts for electrochemical oxygen reduction to replace expensive and rare platinum‐based catalysts is an important issue in energy storage and conversion research. In this context, conductive and porous metal–organic frameworks (MOFs) are considered promising materials for the oxygen reduction reaction (ORR) due to not only their high surface area and well‐developed pores but also versatile structural features and chemical compositions. Herein, the preparation of bimetallic conductive 2D MOFs (Co_xNi_y‐CATs) are reported for use as catalysts in the ORR. The ratio of the two metal ions (Co²⁺ and Ni²⁺) in the bimetallic Co_xNi_y‐CATs is rationally controlled to determine the optimal composition of Co_xNi_y‐CAT for efficient performance in the ORR. Indeed, bimetallic MOFs display enhanced ORR activity compared to their monometallic counterparts (Co‐CAT or Ni‐CAT). During the ORR, bimetallic Co_xNi_y‐CATs retain an advantageous characteristic of Co‐CAT in relation to its high diffusion‐limiting current density, as well as a key advantage of Ni‐CAT in relation to its high onset potential. Moreover, the ORR‐active bimetallic Co_xNi_y‐CAT with excellent ORR activity is prepared at a large scale via a convenient method using a ball‐mill reactor.     

Self-organization of histone-jointed three-dimensional DNA network

A three-dimensional deoxyribonucleic acid (DNA) network was self-organized in a space between two cover slips, which was filled with an aqueous solution of lambda DNA mixed with multivalent cations such as Ca²⁺ and histone; the former behaves as a DNA fixation factor on the cover-slip surface and the latter as a junction and pillar construction factor for the network. The geometry and the components of the three-dimensional DNA network thus formed were observed by fluorescence microscopy. It is revealed that (1) the three-dimensional network is based on two-dimensional networks formed on the inner surfaces of the two cover slips, (2) the three-dimensional network is composed of junctions for forming the two-dimensional networks, chains for connecting two adjacent junctions, and pillars connecting the two-dimensional network on one cover-slip surface to the other, and (3) the chains are made of bundles of stretched lambda DNA molecules, and the junctions and the pillars are made of the aggregates of DNA–histone complexes.     

Hydrogen Trapping in Some Automotive Martensitic Advanced High‐Strength Steels

Hydrogen permeation experiments are used to investigate hydrogen trapping in commercial automotive martensitic advanced high‐strength steels. Hydrogen trapping increases with increasing mechanical strength, as indicated by (i) the decrease in the hydrogen diffusion coefficient, and (ii) the increase in reversible hydrogen trap density. The measured trap densities are in the order of ≈10¹⁷– ≈ 10¹⁸ cm^?3. The relationship between trapping characteristics and HE susceptibility of MS‐AHSS is discussed in terms of Hydrogen Enhanced Macroscopic Plasticity (HEMP) and Hydrogen Assisted Micro‐fracture (HAM).