Engineering a nanoantibiotic system displaying dual mechanism of action.

In recent decades, peptide amphiphiles (PAs) have established themselves as promising self-assembling bioinspired materials in a wide range of medical fields. Herein, we report a dual-therapeutic system constituted by an antimicrobial PA and a cylindrical protease inhibitor (LJC) to achieve broad antimicrobial spectrum and to enhance therapeutic efficacy. We studied two strategies: PA-LJC nanostructures (Encapsulation) and PA nanostructures + free LJC (Combination). Computational modeling using a molecular theory for amphiphile self-assembly captures and explains the morphology of PA-LJC nanostructures and the location of encapsulated LJC in agreement with transmission electron microscopy and two-dimensional (2D) NMR observations. The morphology and release profile of PA-LJC assemblies are strongly correlated to the PA:LJC ratio: high LJC loading induces an initial burst release. We then evaluated the antimicrobial activity of our nanosystems toward gram-positive and gram-negative bacteria. We found that the Combination broadens the spectrum of LJC, reduces the therapeutic concentrations of both agents, and is not impacted by the inoculum effect. Further, the Encapsulation provides additional benefits including bypassing water solubility limitations of LJC and modulating the release of this molecule. The different properties of PA-LJC nanostructures results in different killing profiles, and reduced cytotoxicity and hemolytic activity. Meanwhile, details in membrane alterations caused by each strategy were revealed by various microscopy and fluorescent techniques. Last, in vivo studies in larvae treated by the Encapsulation strategy showed better antimicrobial efficacy than polymyxin B. Collectively, this study established a multifunctional platform using a versatile PA to act as an antibiotic, membrane-penetrating assistant, and slow-release delivery vehicle.

Structural color in the bacterial domain: The ecogenomics of a 2-dimensional optical phenotype.

Structural color is an optical phenomenon resulting from light interacting with nanostructured materials. Although structural color (SC) is widespread in the tree of life, the underlying genetics and genomics are not well understood. Here, we collected and sequenced a set of 87 structurally colored bacterial isolates and 30 related strains lacking SC. Optical analysis of colonies indicated that diverse bacteria from at least two different phyla (Bacteroidetes and Proteobacteria) can create two-dimensional packing of cells capable of producing SC. A pan-genome-wide association approach was used to identify genes associated with SC. The biosynthesis of uroporphyrin and pterins, as well as carbohydrate utilization and metabolism, was found to be involved. Using this information, we constructed a classifier to predict SC directly from bacterial genome sequences and validated it by cultivating and scoring 100 strains that were not part of the training set. We predicted that SCr is widely distributed within gram-negative bacteria. Analysis of over 13,000 assembled metagenomes suggested that SC is nearly absent from most habitats associated with multicellular organisms except macroalgae and is abundant in marine waters and surface/air interfaces. This work provides a large-scale ecogenomics view of SC in bacteria and identifies microbial pathways and evolutionary relationships that underlie this optical phenomenon.

Synthetic peptides that form nanostructured micelles have potent antibiotic and antibiofilm activity against polymicrobial infections.

The emergence of multidrug-resistant bacterial pathogens is a growing threat to global public health. Here, we report the development and characterization of a panel of nine-amino acid residue synthetic peptides that display potent antibacterial activity and the ability to disrupt preestablished microbial biofilms. The lead peptide (Peptide K6) showed bactericidal activity against Pseudomonas aeruginosa and Staphylococcus aureus in culture and in monocultures and mixed biofilms in vitro. Biophysical analysis revealed that Peptide K6 self-assembled into nanostructured micelles that correlated with its strong antibiofilm activity. When surface displayed on the outer membrane protein LamB, two copies of the Peptide K6 were highly bactericidal to Escherichia coli. Peptide K6 rapidly increased the permeability of bacterial cells, and resistance to this toxic peptide occurred less quickly than that to the potent antibiotic gentamicin. Furthermore, we found that Peptide K6 was safe and effective in clearing mixed P. aeruginosa-S. aureus biofilms in a mouse model of persistent infection. Taken together, the properties of Peptide K6 suggest that it is a promising antibiotic candidate and that design of additional short peptides that form micelles represents a worthwhile approach for the development of antimicrobial agents.

Programming the morphology of DNA origami crystals by magnesium ion strength.

Harnessing the programmable nature of DNA origami for controlling structural features in crystalline materials affords opportunities to bring crystal engineering to a remarkable level. However, the challenge of crystallizing a single type of DNA origami unit into varied structural outcomes remains, given the requirement for specific DNA designs for each targeted structure. Here, we show that crystals with distinct equilibrium phases and shapes can be realized using a single DNA origami morphology with an allosteric factor to modulate the binding coordination. As a result, origami crystals undergo phase transitions from a simple cubic lattice to a simple hexagonal (SH) lattice and eventually to a face-centered cubic (FCC) lattice. After selectively removing internal nanoparticles from DNA origami building blocks, the body-centered tetragonal and chalcopyrite lattice are derived from the SH and FCC lattices, respectively, revealing another phase transition involving crystal system conversions. The rich phase space was realized through the de novo synthesis of crystals under varying solution environments, followed by the individual characterizations of the resulting products. Such phase transitions can lead to associated transitions in the shape of the resulting products. Hexagonal prism crystals, crystals characterized by triangular facets, and twinned crystals are observed to form from SH and FCC systems, which have not previously been experimentally realized by DNA origami crystallization. These findings open a promising pathway toward accessing a rich phase space with a single type of building block and wielding other instructions as tools to develop crystalline materials with tunable properties.

Atomic coordination environment engineering of bimetallic alloy nanostructures for efficient ammonia electrosynthesis from nitrate.

Electrochemical nitrate reduction reaction (NO3RR) to ammonia has been regarded as a promising strategy to balance the global nitrogen cycle. However, it still suffers from poor Faradaic efficiency (FE) and limited yield rate for ammonia production on heterogeneous electrocatalysts, especially in neutral solutions. Herein, we report one-pot synthesis of ultrathin nanosheet-assembled RuFe nanoflowers with low-coordinated Ru sites to enhance NO3RR performances in neutral electrolyte. Significantly, RuFe nanoflowers exhibit outstanding ammonia FE of 92.9% and yield rate of 38.68 mg h-1 mgcat-1 (64.47 mg h-1 mgRu-1) at -0.30 and -0.65 V (vs. reversible hydrogen electrode), respectively. Experimental studies and theoretical calculations reveal that RuFe nanoflowers with low-coordinated Ru sites are highly electroactive with an increased d-band center to guarantee efficient electron transfer, leading to low energy barriers of nitrate reduction. The demonstration of rechargeable zinc-nitrate batteries with large-specific capacity using RuFe nanoflowers indicates their great potential in next-generation electrochemical energy systems.

Anelasticity in thin-shell nanolattices.

In this work, we investigate the anelastic deformation behavior of periodic three-dimensional (3D) nanolattices with extremely thin shell thicknesses using nanoindentation. The results show that the nanolattice continues to deform with time under a constant load. In the case of 30-nm-thick aluminum oxide nanolattices, the anelastic deformation accounts for up to 18.1% of the elastic deformation for a constant load of 500 µN. The nanolattices also exhibit up to 15.7% recovery after unloading. Finite element analysis (FEA) coupled with diffusion of point defects is conducted, which is in qualitative agreement with the experimental results. The anelastic behavior can be attributed to the diffusion of point defects in the presence of a stress gradient and is reversible when the deformation is removed. The FEA model quantifies the evolution of the stress gradient and defect concentration and demonstrates the important role of a wavy tube profile in the diffusion of point defects. The reported anelastic deformation behavior can shed light on time-dependent response of nanolattice materials with implication for energy dissipation applications.

Boosting the reaction kinetics in aprotic lithium-carbon dioxide batteries with unconventional phase metal nanomaterials.

Given the high energy density and eco-friendly characteristics, lithium-carbon dioxide (Li-CO2) batteries have been considered to be a next-generation energy technology to promote carbon neutral and space exploration. However, Li-CO2 batteries suffer from sluggish reaction kinetics, causing large overpotential and poor energy efficiency. Here, we observe enhanced reaction kinetics in aprotic Li-CO2 batteries with unconventional phase 4H/face-centered cubic (fcc) iridium (Ir) nanostructures grown on gold template. Significantly, 4H/fcc Ir exhibits superior electrochemical performance over fcc Ir in facilitating the round-trip reaction kinetics of Li+-mediated CO2 reduction and evolution, achieving a low charge plateau below 3.61 V and high energy efficiency of 83.8%. Ex situ/in situ studies and theoretical calculations reveal that the boosted reaction kinetics arises from the highly reversible generation of amorphous/low-crystalline discharge products on 4H/fcc Ir via the Ir-O coupling. The demonstration of flexible Li-CO2 pouch cells with 4H/fcc Ir suggests the feasibility of using unconventional phase nanomaterials in practical scenarios.

Mechanism of shaping membrane nanostructures of endoplasmic reticulum.

Recent advances in super-resolution microscopy revealed the previously unknown nanoscopic level of organization of endoplasmic reticulum (ER), one of the most vital intracellular organelles. Membrane nanostructures of 10- to 100-nm intrinsic length scales, which include ER tubular matrices, ER sheet nanoholes, internal membranes of ER exit sites (ERES), and ER transport intermediates, were discovered and imaged in considerable detail, but the physical factors determining their unique geometrical features remained unknown. Here, we proposed and computationally substantiated a common concept for mechanisms of all ER nanostructures based on the membrane intrinsic curvature as a primary factor shaping the membrane and ultra-low membrane tensions as modulators of the membrane configurations. We computationally revealed a common structural motif underlying most of the nanostructures. We predicted the existence of a discrete series of equilibrium configurations of ER tubular matrices and recovered the one corresponding to the observations and favored by ultra-low tensions. We modeled the nanohole formation as resulting from a spontaneous collapse of elements of the ER tubular network adjacent to the ER sheet edge and calculated the nanohole dimensions. We proposed the ERES membrane to have a shape of a super flexible membrane bead chain, which acquires random walk configurations unless an ultra-low tension converts it into a straight conformation of a transport intermediate. The adequacy of the proposed concept is supported by a close qualitative and quantitative similarity between the predicted and observed configurations of all four ER nanostructures.

Phase Behavior Modulation of a Unary DNA Origami System through Allosteric Stimuli.

A unary system is the most conceptually concise design for conducting self-assembly. However, in most DNA-guided self-assembly schemes, a unary system has rarely been adopted because of the inherent challenge of strictly decoupling the monomer synthesis process from the assembly process, which may directly lead to the inaccurate control over assembly. Herein, we provide a multi-stimulus-triggered assembly strategy based on the DNA origami structure, which allows the unary system to realize controllable crystallization and phase transition by exerting allosteric stimuli. We intentionally introduced a specific DNA stimulus to convert the self-aggregation of functionalized groups into the connection of nearby monomers, thus producing multidimensional high-quality crystals. Furthermore, this unary system can undergo a phase transition from simple cubic to face-centered cubic with the introduction of more cation stimuli. We believe that this dynamic stimulation strategy can offer a novel solution for fabricating materials with on-demand modulation.

STORM Super-Resolution Visualization of Self-Assembled γPFD Chaperone Ultrastructures in Methanocaldococcus jannaschii.

Gamma-prefoldin (γPFD), a unique chaperone found in the extremely thermophilic methanogen Methanocaldococcus jannaschii, self-assembles into filaments in vitro, which so far have been observed using transmission electron microscopy and cryo-electron microscopy. Utilizing three-dimensional stochastic optical reconstruction microscopy (3D-STORM), here we achieve ∼20 nm resolution by precisely locating individual fluorescent molecules, hence resolving γPFD ultrastructure both in vitro and in vivo. Through CF647 NHS ester labeling, we first demonstrate the accurate visualization of filaments and bundles with purified γPFD. Next, by implementing immunofluorescence labeling after creating a 3xFLAG-tagged γPFD strain, we successfully visualize γPFD in M. jannaschii cells. Through 3D-STORM and two-color STORM imaging with DNA, we show the widespread distribution of filamentous γPFD structures within the cell. These findings provide valuable insights into the structure and localization of γPFD, opening up possibilities for studying intriguing nanoscale components not only in archaea but also in other microorganisms.

Customized Self-Assembled Gold Nanoparticle-DNA Origami Composite Templates for Shape-Directed Growth of Plasmonic Structures.

The metal plasmonic nanostructure has the optical property of plasmon resonance, which holds great potential for development in nanophotonics, bioelectronics, and molecular detection. However, developing a general and straightforward method to prepare metal plasmonic nanostructures with a controllable size and morphology still poses a challenge. Herein, we proposed a synthesis strategy that utilized a customizable self-assembly template for shape-directed growth of metal structures. We employed gold nanoparticles (AuNPs) as connectors and DNA nanotubes as branches, customizing gold nanoparticle-DNA origami composite nanostructures with different branches by adjusting the assembly ratio between the connectors and branches. Subsequently, various morphologies of plasmonic metal nanostructures were created using this template shape guided strategy, which exhibited enhancement of surface-enhanced Raman scattering (SERS) signals. This strategy provides a new approach for synthesizing metallic nanostructures with multiple morphologies and opens up another possibility for the development of customizable metallic plasmonic structures with broader applications.

Temporal (Dis)Assembly of Peptide Nanostructures Dictated by Native Multistep Catalytic Transformations.

Emergence of complex catalytic machinery via simple building blocks under non-equilibrium conditions can contribute toward the system level understanding of the extant biocatalytic reaction network that fuels metabolism. Herein, we report temporal (dis)assembly of peptide nanostructures in presence of a cofactor dictated by native multistep cascade transformations. The short peptide can form a dynamic covalent bond with the thermodynamically activated substrate and recruit cofactor hemin to access non-equilibrium catalytic nanostructures (positive feedback). The neighboring imidazole and hemin moieties in the assembled state rapidly converted the substrate to product(s) via a two-step cascade reaction (hydrolase-peroxidase like) that subsequently triggered the disassembly of the catalytic nanostructures (negative feedback). The feedback coupled reaction cycle involving intrinsic catalytic prowess of short peptides to realize the advanced trait of two-stage cascade degradation of a thermodynamically activated substrate foreshadows the complex non-equilibrium protometabolic networks that might have preceded the chemical emergence of life.

Surface Coloring and Plasmonic Information Encryption at 50000 dpi Enabled by Direct Femtosecond Laser Printing.

Femtosecond (fs) laser pulses drive matter into a highly nonequilibrium state, allowing precise sculpturing of irradiated surface sites with sophisticated nanomorphologies. Here, we used fs-laser patterning to create diverse plasmonic morphologies on the top Au layer of the metal-insulator-metal sandwich. Mutual action of laser-driven thermomechanical effects and ultrafast solid-to-liquid transition allows control of the morphology resulting in pronounced surface reflectivity modulation, i.e., in a structural color effect. This enables template-free high-resolution color printing at a superior lateral resolution up to 50000 dots per inch and facile tunability of the color tone and saturation. Moreover, precise control over the orientation of the printed nanostructures within subwavelength lattices allows modulation of their local plasmonic response encrypting the optical information within the colorful images. The hidden information can be unveiled using a facile cross-polarized optical visualization scheme, rendering the proposed method with extra modalities combining high resolution information encryption, coloring, and security labeling.

Demonstration of Controlled Skyrmion Injection Across a Thickness Step.

Spintronic devices incorporating magnetic skyrmions have attracted significant interest recently. Such devices traditionally focus on controlling magnetic textures in 2D thin films. However, enhanced performance of spintronic properties through the exploitation of higher dimensionalities motivates the investigation of variable-thickness skyrmion devices. We report the demonstration of a skyrmion injection mechanism that utilizes charge currents to drive skyrmions across a thickness step and, consequently, a metastability barrier. Our measurements show that under certain temperature and field conditions skyrmions can be reversibly injected from a thin region of an FeGe lamella, where they exist as an equilibrium state, into a thicker region, where they can only persist as a metastable state. This injection is achieved with a current density of 3 × 108 A m-2, nearly 3 orders of magnitude lower than required to move magnetic domain walls. This highlights the possibility to use such an element as a skyrmion source/drain within future spintronic devices.

Electron Imaging of Nanoscale Charge Distributions Induced by Femtosecond Light Pulses.

Surface charging is ubiquitously observable during in situ transmission electron microscopy of nonconducting specimens as a result of electron beam/sample interactions or optical stimuli and often limits the achievable image stability and spatial or spectral resolution. Here, we report on the electron-optical imaging of surface charging on a nanostructured surface following femtosecond multiphoton photoemission. By quantitatively extracting the light-induced electrostatic potential and studying the charging dynamics on relevant time scales, we gain insights into the details of the multiphoton photoemission process in the presence of an electrostatic background field. We study the interaction of the charge distribution with the high-energy electron beam and secondary electrons and propose a simple model to describe the interplay of electron- and light-induced processes. In addition, we demonstrate how to mitigate sample charging by simultaneously optically illuminating the sample.

Self-Driven, Monopolar Electrohydrodynamic Printing via Dielectric Nanoparticle Layer.

Electrohydrodynamic printing holds both ultrahigh-resolution fabrication capability and unmatched ink-viscosity compatibility yet fails on highly insulating thick/irregular substrates. Herein, we proposed a single-potential driven electrohydrodynamic printing process with submicrometer resolution on arbitrary nonconductive targets, regardless of their geometric shape or sizes, via precoating with an ultrathin dielectric nanoparticle layer. Benefiting from the favorable Maxwell-Wagner polarization, the reversely polarized spot brought about a significant drop (∼57% for ceramics) in the operation voltage as its induced electric field and a negligible residual charge accumulation. Thus, ordered micro/nanostructures with line widths down to 300 nm were directly written at a stage speed as low as 5 mm/s, and silver features with width of ∼2 µm or interval of ∼4 µm were achieved on insulating substrates separately. Flexible sensors and curved heaters were then high-precision printed and demonstrated successfully, presenting this technique with huge potential for fabricating flexible/conformal electronics on arbitrary 3D structures.

Surface-Patterned DNA Origami Rulers Reveal Nanoscale Distance Dependency of the Epidermal Growth Factor Receptor Activation.

The nanoscale arrangement of ligands can have a major effect on the activation of membrane receptor proteins and thus cellular communication mechanisms. Here we report on the technological development and use of tailored DNA origami-based molecular rulers to fabricate "Multiscale Origami Structures As Interface for Cells" (MOSAIC), to enable the systematic investigation of the effect of the nanoscale spacing of epidermal growth factor (EGF) ligands on the activation of the EGF receptor (EGFR). MOSAIC-based analyses revealed that EGF distances of about 30-40 nm led to the highest response in EGFR activation of adherent MCF7 and Hela cells. Our study emphasizes the significance of DNA-based platforms for the detailed investigation of the molecular mechanisms of cellular signaling cascades.

Tuning the Chiral Growth of Plasmonic Bipyramids via the Wavelength and Polarization of Light.

Circularly polarized light (CPL) is a versatile tool to prepare chiral nanostructures, but the mechanism for inducing enantioselectivity is not well understood. This work shows that the energy and polarization of visible photons can initiate photodeposition at different sites on plasmonic nanocrystals. Here, CPL on achiral gold bipyramids (AuBPs) creates hot holes that oxidatively deposit PbO2 asymmetrically. We show for the first time that the location of PbO2 photodeposition and hence optical dissymmetry depends on the CPL wavelength. Specifically, 488 and 532 nm CPL induce PbO2 growth in the middle of AuBPs, whereas 660 nm CPL induces PbO2 growth at the tips. Our observations show that wavelength-dependent plasmonic field distributions are more important than surface lightning rod effects in localizing plasmon-mediated photochemistry. The largest optical dissymmetry occurs at excitation wavelengths between the transverse and longitudinal resonances of the AuBPs because higher-order modes are required to induce chiral electric fields.

Heavy Metal Stabilization of DNA Origami Nanostructures.

DNA origami is a powerful tool to fold 3-dimensional DNA structures with nanometer precision. Its usage, however, is limited as high ionic strength, temperatures below ∼60 °C, and pH values between 5 and 10 are required to ensure the structural integrity of DNA origami nanostructures. Here, we demonstrate a simple and effective method to stabilize DNA origami nanostructures against harsh buffer conditions using [PdCl4]2-. It provided the stabilization of different DNA origami nanostructures against mechanical compression, temperatures up to 100 °C, double-distilled water, and pH values between 4 and 12. Additionally, DNA origami superstructures and bound cargos are stabilized with yields of up to 98%. To demonstrate the general applicability of our approach, we employed our protocol with a Pd metallization procedure at elevated temperatures. In the future, we think that our method opens up new possibilities for applications of DNA origami nanostructures beyond their usual reaction conditions.

Self-Driven Graphene Photodetector Arrays Enabled by Plasmon-Induced Asymmetric Electric Field.

Gap surface plasmon (GSP) modes enhance graphene photodetectors (GPDs)' performance by confining the incident light within nanogaps, giving rise to strong light absorption. Here, we propose an asymmetric plasmonic nanostructure array on planar graphene comprising stripe- and triangle-shaped sharp tip arrays. Upon light excitation, the noncentrosymmetric metallic nanostructures show strong light-matter interactions with localized field close to the surface of tips, causing an asymmetric electric field. These features can accelerate the hot electron generation in graphene, forming a directional diffusion current. Accordingly, the artificial GPDs exhibit a wavelength-dependence behavior covering the wavelength range from 0.8 to 1.6 µm, with three photoresponse maxima corresponding to the nanostructures' resonances. Additionally, the polarization-dependent GPDs can realize a responsivity of ∼25 mA/W and a noise equivalent power of ∼0.44 nW/Hz1/2 at zero bias when excited at the resonance of 1.4 µm. Overall, our study offers a new strategy for preparing compact and multifrequency infrared GPDs.