Spiral Patterning of Au Nanoparticles on Au Nanorod Surface to Form Chiral AuNR@AuNP Helical Superstructures Templated by DNA Origami

Plasmonic motifs with precise surface recognition sites are crucial for assembling defined nanostructures with novel functionalities and properties. In this work, a unique and effective strategy is successfully developed to pattern DNA recognition sites in a helical arrangement around a gold nanorod (AuNR), and a new set of heterogeneous AuNR@AuNP plasmonic helices is fabricated by attaching complementary‐DNA‐modified gold nanoparticles (AuNPs) to the predesigned sites on the AuNR surface. AuNR is first assembled to one side of a bifacial rectangular DNA origami, where eight groups of capture strands are selectively patterned on the other side. The subsequently added link strands make the rectangular DNA origami roll up around the AuNR into a tubular shape, therefore giving birth to a chiral patterning of DNA recognition sites on the surface of AuNR. Following the hybridization with the AuNPs capped with the complementary strands to the capture strands on the DNA origami, left‐handed and right‐handed AuNR@AuNP helical superstructures are precisely formed by tuning the pattern of the recognition sites on the AuNR surface. Our strategy of nanoparticle surface patterning innovatively realizes hierarchical self‐assembly of plasmonic superstructures with tunable chiroptical responses, and will certainly broaden the horizon of bottom‐up construction of other functional nanoarchitectures with growing complexity.     

Encapsulation of Gold Nanoparticles into DNA Minimal Cages for 3D‐Anisotropic Functionalization and Assembly

Gold nanoparticles (AuNPs) endowed with anisotropic DNA valency are an important class of materials, as they can assemble into complex structures with a minimal number of DNA strands. However, methods to encode 3D DNA strand patterns on AuNPs with a controlled number of unique DNA strands in a predesigned spatial arrangement remain elusive. In this work, a simple one‐step method to yield such DNA‐decorated AuNPs is demonstrated, through encapsulating AuNPs into DNA minimal nanocages. The AuNP@DNA cage encapsulation complex inherits the 3D anisotropic molecular information from the DNA nanocage with enhanced structural stability. The DNA nanocage can be further functionalized and used as a building block for the self‐assembly of complex architectures, such as dimers and trimers, programmed assemblies with sequential growth DNA backbones and DNA origami.     

Humidity‐Responsive Single‐Nanoparticle‐Layer Plasmonic Films

2D materials possess many interesting properties, and have shown great application potentials. In this work, the development of humidity‐responsive, 2D plasmonic nanostructures with switchable chromogenic properties upon wetting–dewetting transitions is reported. By exploiting DNA hybridization‐directed anchoring of gold nanoparticles (AuNPs) on substrates, a series of single‐nanoparticle‐layer (SNL) plasmonic films is fabricated. Due to the collective plasmonic responses in SNL, these ultrathin 2D films display rapid and reversible red‐blue color change upon the wetting–dewetting transition, suggesting that hydration‐induced microscopic plasmonic coupling between AuNPs is replicated in the macroscopic, centimeter‐scale films. It is also found that hydration finely tunes the electric field distribution between AuNPs in the SNL film, based on which responsive surface‐enhanced Raman scattering substrates with spatially homogeneous hot spots are developed. Thus it is expected that DNA‐mediated 2D SNL structures open new avenues for designing miniaturized plasmonic nanodevices with various applications.     

Polymer‐Based Stimuli‐Responsive Recyclable Catalytic Systems for Organic Synthesis

The introduction of stimuli‐responsive polymers into the study of organic catalysis leads to the generation of a new kind of polymer‐based stimuli‐responsive recyclable catalytic system. Owing to their reversible switching properties in response to external stimuli, these systems are capable of improving the mass transports of reactants/products in aqueous solution, modulating the chemical reaction rates, and switching the catalytic process on and off. Furthermore, their stimuli‐responsive properties facilitate the separation and recovery of the active catalysts from the reaction mixtures. As a fascinating approach of the controllable catalysis, these stimuli‐responsive catalytic systems including thermoresponsive, pH‐responsive, chemo‐mechano‐chemical, ionic strength‐responsive, and dual‐responsive, are reviewed in terms of their nanoreactors and mechanisms.     

Directed Assembly of Gold Nanorods by Terminal‐Base Pairing of Surface‐Grafted DNA

Directed assemblies of anisotropic metal nanoparticles exhibit attractive physical and chemical properties. However, an effective methodology to prepare differently directed assemblies from the same anisotropic nanoparticles is not yet available. Gold nanorods (AuNRs) region‐selectively modified with different DNA strands can form side‐by‐side (SBS) and end‐to‐end (ETE) assemblies in a non‐crosslinking manner. When the complementary DNA is hybridized to the surface‐bound DNA, stacking interaction between the blunt ends takes place in the designated regions. Such AuNRs assemble into highly ordered structures, assisted by capillary forces emerging on the substrate surface. Moreover, insertion of a mercury(II)‐mediated thymine–thymine base pair into the periphery of the DNA layer allows selective formation of the SBS or ETE assemblies from the strictly identical AuNRs with or without mercury(II).     

Programmed Nanoparticle‐Loaded Nanoparticles for Deep‐Penetrating 3D Cancer Therapy

Tumors are 3D, composed of cellular agglomerations and blood vessels. Therapies involving nanoparticles utilize specific accumulations due to the leaky vascular structures. However, systemically injected nanoparticles are mostly uptaken by cells located on the surfaces of cancer tissues, lacking deep penetration into the core cancer regions. Herein, an unprecedented strategy, described as injecting “nanoparticle‐loaded nanoparticles” to address the long‐lasting problem is reported for effective surface‐to‐core drug delivery in entire 3D tumors. The “nanoparticle‐loaded nanoparticle” is a silica nanoparticle (≈150 nm) with well‐developed, interconnected channels (diameter of ≈30 nm), in which small gold nanoparticles (AuNPs) (≈15 nm) with programmable DNA are located. The nanoparticle (AuNPs)‐loaded nanoparticles (silica): (1) can accumulate in tumors through leaky vascular structures by protecting the inner therapeutic AuNPs during blood circulation, and then (2) allow diffusion of the AuNPs for penetration into the entire surface‐to‐core tumor tissues, and finally (3) release a drug triggered by cancer‐characteristic pH gradients. The hierarchical “nanoparticle‐loaded nanoparticle” can be a rational design for cancer therapies because the outer large nanoparticles are effective in blood circulation and in protection of the therapeutic nanoparticles inside, allowing the loaded small nanoparticles to penetrate deeply into 3D tumors with anticancer drugs.     

Size‐Dependent Toxicity of Gold Nanoparticles on Human Embryonic Stem Cells and Their Neural Derivatives

This study explores the use of human embryonic stem cells (hESCs) for assessing nanotoxicology, specifically, the effect of gold nanoparticles (AuNPs) of different core sizes (1.5, 4, and 14 nm) on the viability, pluripotency, neuronal differentiation, and DNA methylation of hESCs. The hESCs exposed to 1.5 nm thiolate‐capped AuNPs exhibit loss of cohesiveness and detachment suggesting ongoing cell death at concentrations as low as 0.1 μg mL^?1. The cells exposed to 1.5 nm AuNPs at this concentration do not form embryoid bodies but rather disintegrate into single cells within 48 h. Cell death caused by 1.5 nm AuNPs also occur in hESC‐derived neural progenitor cells. None of the other nanoparticles exhibit toxic effects on the hESCs at concentrations as high as 10 μg mL^?1 during a 19 d neural differentiation period. Thiolate‐capped 4 nm AuNPs at 10 μg mL^?1 cause a dramatic decrease in global DNA methylation (5 mC) and a corresponding increase in global DNA hydroxymethylation (5 hmC) of the hESC's DNA in only 24 h. This work identifies a type of AuNPs highly toxic to hESCs and demonstrates the potential of hESCs in predicting nanotoxicity and characterizing their ability to alter the DNA methylation and hydroxymethylation patterns in the cells.     

Reactivating Catalytic Surface: Insights into the Role of Hot Holes in Plasmonic Catalysis

Surface plasmon resonance of coinage metal nanoparticles is extensively exploited to promote catalytic reactions via harvesting solar energy. Previous efforts on elucidating the mechanisms of enhanced catalysis are devoted to hot electron‐induced photothermal conversion and direct charge transfer to the adsorbed reactants. However, little attention is paid to roles of hot holes that are generated concomitantly with hot electrons. In this work, 13 nm spherical Au nanoparticles with small absorption cross‐section are employed to catalyze a well‐studied glucose oxidation reaction. Density functional theory calculation and X‐ray absorption spectrum analysis reveal that hot holes energetically favor transferring catalytic intermediates to product molecules and then desorbing from the surface of plasmonic catalysts, resulting in the recovery of their catalytic activities. The studies shed new light on the use of the synergy of hot holes and hot electrons for plasmon‐promoted catalysis.     

Nanoparticle‐Induced Folding and Fibril Formation of Coiled‐Coil‐Based Model Peptides

Nanomedicine is a rapidly growing field that has the potential to deliver treatments for many illnesses. However, relatively little is known about the biological risks of nanoparticles. Some studies have shown that nanoparticles can have an impact on the aggregation properties of proteins, including fibril formation. Moreover, these studies also show that the capacity of nanoscale objects to induce or prevent misfolding of the proteins strongly depends on the primary structure of the protein. Herein, light is shed on the role of the peptide primary structure in directing nanoparticle‐induced misfolding by means of two model peptides. The design of these peptides is based on the α‐helical coiled‐coil folding motif, but also includes features that enable them to respond to pH changes, thus allowing pH‐dependent β‐sheet formation. Previous studies showed that the two peptides differ in the pH range required for β‐sheet folding. Time‐dependent circular dichroism spectroscopy and transmission electron microscopy are used to characterize peptide folding and aggregate morphology in the presence of negatively charged gold nanoparticles (AuNPs). Both peptides are found to undergo nanoparticle‐induced fibril formation. The determination of binding parameters by isothermal titration calorimetry further reveals that the different propensities of both peptides to form amyloid‐like structures in the presence of AuNPs is primarily due to the binding stoichiometry to the AuNPs. Modification of one of the peptide sequences shows that AuNP‐induced β‐sheet formation is related to the structural propensity of the primary structure and is not a generic feature of peptide sequences with a sufficiently high binding stoichiometry to the nanoparticles.     

Cu‐induced assembly of methanobactin‐modified gold nanoparticles and its peroxidase mimic activity

Methanobactin (Mb) is a small copper‐chelating molecule that functions as an agent for copper acquisition, uptake and copper‐containing methane monooxygenase catalysis in methane‐oxidising bacteria. The UV–visible spectral and fluorescence spectral suggested that Mb/Cu coordination complex as a monomer (Mb‐Cu), dimmer (Mb₂ ‐Cu) and tetramer (Mb₄ ‐Cu) could be obtained at different ratios of Mb to Cu (II). The kinetics of the oxidation of hydroquinone with hydrogen peroxide catalysed by the different Mb/Cu coordination complex were investigated. The results suggested that Mb₂ ‐Cu coordination form has highest catalytic capacity. Further, Mb‐modified gold nanoparticles (AuNPs) were obtained by ligand exchange and assembled into two‐ and three‐D nanocluster structure by metal‐organic coordination as driving force. It has been found that AuNPs increased the catalytic activity of Mb₂ ‐Cu on AuNPs. The more significant catalytic activity was exhibited by the nanocluster assembly with multi‐catalytic centres. This may be attributed to the multivalent collaborative characteristics of the catalytic active centres in the nanocluster network assembly. The assembly of Mb‐modified AuNPs can act as excellent nanoenzyme models for imitating peroxidase.Inspec keywords: nanoparticles, catalysis, oxidation, enzymes, microorganisms, nanobiotechnology, gold, organic compounds, reduction (chemical), visible spectra, molecular biophysics, ultraviolet spectra, biochemistry, copper, nanofabrication, fluorescenceOther keywords: Mb‐modified gold nanoparticles, catalytic active centres, Mb‐modified AuNPs, Cu‐induced assembly, methanobactin‐modified gold nanoparticles, peroxidase mimic activity, copper‐chelating molecule, copper‐containing methane monooxygenase catalysis, methane‐oxidising bacteria, fluorescence, Mb/Cu coordination complex, catalytic activity, UV–visible spectra, nanocluster assembly, Cu, Au     

Size‐Dependent Phase Transformation of Noble Metal Nanomaterials

As an important aspect of crystal phase engineering, controlled crystal phase transformation of noble metal nanomaterials has emerged as an effective strategy to explore novel crystal phases of nanomaterials. In particular, it is of significant importance to observe the transformation pathway and reveal the transformation mechanism in situ. Here, the phase transformation behavior of face‐centered cubic (fcc) Au nanoparticles (fcc‐AuNPs), adhering to the surface of 4H nanodomains in 4H/fcc Au nanorods, referred to as 4H‐AuNDs, during in situ transmission electron microscopy imaging is systematically studied. It is found that the phase transformation is dependent on the ratio of the size of the monocrystalline nanoparticle (NP) to the diameter of 4H‐AuND. Furthermore, molecular dynamics simulation and theoretical modeling are used to explain the experimental results, giving a size‐dependent phase transformation diagram which provides a general guidance to predict the phase transformation pathway between fcc and 4H Au nanomaterials. Impressively, this method is general, which is used to study the phase transformation of other metal NPs, such as Pd, Ag, and PtPdAg, adhering to 4H‐AuNDs. The work opens an avenue for selective phase engineering of nanomaterials which may possess unique physicochemical properties and promising applications.     

High Density Unaggregated Au Nanoparticles on ZnO Nanorod Arrays Function as Efficient and Recyclable Photocatalysts for Environmental Purification

Photodegradation of organic pollutants in aqueous solution is a promising method for environmental purification. Photocatalysts capable of promoting this reaction are often composed of noble metal nanoparticles deposited on a semiconductor. Unfortunately, the separation of these semiconductor‐metal nanopowders from the treated water is very difficult and energy consumptive, so their usefulness in practical applications is limited. Here, a precisely controlled synthesis of a large‐scale and highly efficient photocatalyst composed of monolayered Au nanoparticles (AuNPs) chemically bound to vertically aligned ZnO nanorod arrays (ZNA) through a bifunctional surface molecular linker is demonstrated. Thioctic acid with sufficient steric stabilization is used as a molecular linker. High density unaggregated AuNPs bonding on entire surfaces of ZNA are successfully prepared on a conductive film/substrate, allowing easy recovery and reuse of the photocatalysts. Surprisingly, the ZNA‐AuNPs heterostructures exhibit a photodegradation rate 8.1 times higher than that recorded for the bare ZNA under UV irradiation. High density AuNPs, dispersed perfectly on the ZNA surfaces, significantly improve the separation of the photogenerated electron‐hole pairs, enlarge the reaction space, and consequently enhance the photocatalytic property for degradation of chemical pollutants. Photoelectron, photoluminescence and photoconductive measurements confirm the discussion on the charge carrier separation and photocatalytic experimental data. The demonstrated higher photodegradation rates demonstrated indicate that the ZNA‐AuNPs heterostructures are candidates for the next‐generation photocatalysts, replacing the conventional slurry photocatalysts.     

Synthesis and Assembly of Click‐Nucleic‐Acid‐Containing PEG–PLGA Nanoparticles for DNA Delivery

Co‐delivery of both chemotherapy drugs and siRNA from a single delivery vehicle can have a significant impact on cancer therapy due to the potential for overcoming issues such as drug resistance. However, the inherent chemical differences between charged nucleic acids and hydrophobic drugs have hindered entrapment of both components within a single carrier. While poly(ethylene glycol)‐block‐poly(lactic‐co‐glycolic acid) (PEG–PLGA) copolymers have been used successfully for targeted delivery of chemotherapy drugs, loading of DNA or RNA has been poor. It is demonstrated that significant amounts of DNA can be encapsulated within PLGA‐containing nanoparticles through the use of a new synthetic DNA analog, click nucleic acids (CNAs). First, triblock copolymers of PEG‐CNA‐PLGA are synthesized and then formulated into polymer nanoparticles from oil‐in‐water emulsions. The CNA‐containing particles show high encapsulation of DNA complementary to the CNA sequence, whereas PEG‐PLGA alone shows minimal DNA loading, and non‐complementary DNA strands do not get encapsulated within the PEG‐CNA‐PLGA nanoparticles. Furthermore, the dye pyrene can be successfully co‐loaded with DNA and lastly, a complex, larger DNA sequence that contains an overhang complementary to the CNA can also be encapsulated, demonstrating the potential utility of the CNA‐containing particles as carriers for chemotherapy agents and gene silencers.     

Anionic Lipid,pH‐Sensitive Liposome‐Gold Nanoparticle Hybrids for Gene Delivery – Quantitative Research of the Mechanism

Gene therapy is a potential method for treating a large range of diseases. Gene vectors are widely used in gene therapy for promoting the gene delivery efficiency to the target cells. Here, gold nanoparticles (AuNPs) coated with dimethyldioctadecylammonium bromide (DODAB)/dioleoylphosphatidylethanolamine (DOPE) are synthesized using a facile method for a new gene vector (DODAB/DOPE‐AuNPs), which possess 3‐ and 1.5‐fold higher transfection efficiency than those of DODAB‐AuNPs and a commercial transfection agent, respectively. Meanwhile, it is nontoxic with concentrations required for effective gene delivery. Imaging and quantification studies of cellular uptake reveal that DOPE increases gene copies in cells, which may be attributed to the smaller size of AuNPs/DNA complexes. The dissociation efficiency of DNA from the endocytic pathway is quantified by incubating with different buffers and investigated directly in the cells. The results suggest that DOPE increases the internalization of AuNPs/DNA complexes and promotes DNA release from early endosomes for the vector is sensitive to the anionic lipid membrane and the decreasing pH along the endocytic pathway. The new vector contains the potential to be the new alternative as gene delivery vector for biomedical applications.     

Sharpening the Thermal Release of DNA from Nanoparticles: Towards a Sequential Release Strategy

Unlike the sharp melting behavior of DNA‐linked nanoparticle aggregates, the melting of DNA strands from individual gold nanoparticles is broad despite the high surface density of bound DNA. Here, it is demonstrated how sharpened melting can be achieved in colloidal nanoparticle systems using branched DNA–doubler structures hybridized with complementary DNA‐doublers bound to the gold nanoparticle. Moreover, sharpened transitions are observed when DNA‐doublers are hybridized with linear DNA‐modified gold nanoparticles. This result suggests that the DNA density on nanoparticles is intrinsically great enough to form cooperative structures with the DNA‐doublers. Finally, by introducing abasic destabilizing groups, the melting temperature of these DNA‐doublers decreases without decreasing the sharpness. Consequently, by varying the temperature, two DNA‐doublers with different stabilities dissociate sequentially from the gold nanoparticle surface, without overlapping and within a narrow temperature window. Owing to the excellent thermal selectivities exhibited by this system, the implementation of DNA‐doublers in sequential photothermal therapies and with other nanomedicine delivery agents that rely on DNA dissociation as the mechanism of selective release is anticipated.     

Lighting Up MicroRNA in Living Cells by the Disassembly of Lock‐Like DNA‐Programmed UCNPs‐AuNPs through the Target Cycling Amplification Strategy

Intracellular microRNAs imaging based on upconversion nanoprobes has great potential in cancer diagnostics and treatments. However, the relatively low detection sensitivity limits their application. Herein, a lock‐like DNA (LLD) generated by a hairpin DNA (H1) hybridizing with a bolt DNA (bDNA) sequence is designed, which is used to program upconversion nanoparticles (UCNPs, NaYF₄@NaYF₄:Yb, Er@NaYF₄) and gold nanoparticles (AuNPs). The upconversion emission is quenched through luminescence resonance energy transfer (LRET). The multiple LLD can be repeatedly opened by one copy of target microRNA under the aid of fuel hairpin DNA strands (H2) to trigger disassembly of AuNPs from the UCNP, resulting in the lighting up of UCNPs with a high detection signal gain. This strategy is verified using microRNA‐21 as model. The expression level of microRNA‐21 in various cells lines can be sensitively measured in vitro, meanwhile cancer cells and normal cells can be easily and accurately distinguished by intracellular microRNA‐21 imaging via the nanoprobes. The detection limit is about 1000 times lower than that of the previously reported upconversion nanoprobes without signal amplification. This is the first time a nonenzymatic signal amplification method has been combined with UCNPs for imaging intracellular microRNAs, which has great potential for cancer diagnosis.     

Engineering Single‐Atom Cobalt Catalysts toward Improved Electrocatalysis

The development of cost‐effective catalysts to replace noble metal is attracting increasing interests in many fields of catalysis and energy, and intensive efforts are focused on the integration of transition‐metal sites in carbon as noble‐metal‐free candidates. Recently, the discovery of single‐atom dispersed catalyst (SAC) provides a new frontier in heterogeneous catalysis. However, the electrocatalytic application of SAC is still subject to several theoretical and experimental limitations. Further advances depend on a better design of SAC through optimizing its interaction with adsorbates during catalysis. Here, distinctive from previous studies, favorable 3d electronic occupation and enhanced metal–adsorbates interactions in single‐atom centers via the construction of nonplanar coordination is achieved, which is confirmed by advanced X‐ray spectroscopic and electrochemical studies. The as‐designed atomically dispersed cobalt sites within nonplanar coordination show significantly improved catalytic activity and selectivity toward the oxygen reduction reaction, approaching the benchmark Pt‐based catalysts. More importantly, the illustration of the active sites in SAC indicates metal‐natured catalytic sites and a media‐dependent catalytic pathway. Achieving structural and electronic engineering on SAC that promotes its catalytic performances provides a paradigm to bridge the gap between single‐atom catalysts design and electrocatalytic applications.     

Design of pH-responsive gold nanoparticles in oncology

Gold nanoparticles (AuNPs) hold promising applications in many fields such as electronics, optics and catalysis. In the past decades, there has been a growing interest for their application in medicine, in particular in nano-oncology as contrast agents, drug delivery vehicles or for diagnosis. Once injected intravenously and thanks to their small size, the AuNPs can circulate in the whole body via the blood stream and reach easily the tumour. However, what makes them very attractive for cancer treatment is their ability to distinguish healthy cells from cancer cells. While the current anticancer agents lack specific targeting, AuNPs, with their targeting efficiency, will enable the use of lower amount of drugs with all the positive aspects for the health of the patient. Additionally, their optical properties give them the ability to be used in imaging as an incredibly powerful contrast agent. For these reasons, they are believed to be one of the tools that, in the future, will enable to considerably increase the efficiency of cancer treatments by simultaneously imaging the tumour and treat it. They constitute an ideal theranostic drug delivery platform, in other words a unique combination of diagnostics and therapy. Many researches focus on the engineering of the nanoparticle surface in order to increase their biocompatibility and enable their further conjugation with bioactive ligands such as drugs, targeting or imaging agents for the design of multifunctional platforms. pH responsiveness, the ability to change properties with a change of proton concentration, is a remarkable asset for drug delivery carrier. Indeed, it has been demonstrated that cancer cells show very particular pHs in their environment: extracellular as well as intracellular. This characteristic has been exploited to create a more specific and efficient way to treat cancer. The present review focuses on the design of pH responsive AuNPs and particularly on the advantages and the potential applications of such hybrid nanomaterials in oncology.     

Antibacterial and catalytic activity of biogenic gold nanoparticles synthesised by Trichoderma harzianum

This study reveals the antibacterial and catalytic activity of biogenic gold nanoparicles (AuNPs) synthesised by biomass of Trichoderma harzianum. The antibacterial activity of AuNPs was analysed by the means of growth curve, well diffusion and colony forming unit (CFU) count methods. The minimum inhibitory concentration of AuNPs was 20 µg/ml. AuNPs at 60 µg/ml show effective antibacterial activity as optical absorption was insignificant. The well diffusion and CFU methods were also applied to analyse the effect of various concentration of AuNPs. Further, the catalytic activity of AuNPs was analysed against methylene blue (MB) as a model pollutant in water. MB was degraded 39% in 30 min in the presence of AuNPs and sodium borohydrate and the rate constant (k) was found to be 0.2 × 10⁻³ s⁻¹. This shows that the biogenic AuNP is an effective candidate for antibacterial and catalytic degradation of toxic pollutants.Inspec keywords: antibacterial activity, catalysis, nanoparticles, gold, nanofabrication, biomedical materials, nanomedicine, renewable materials, surface diffusion, dyes, water pollution, reaction rate constants, toxicologyOther keywords: antibacterial activity, catalytic activity, biogenic gold nanoparticles, Trichoderma harzianum, biomass, growth curve, diffusion, colony forming unit count methods, minimum inhibitory concentration, optical absorption, CFU methods, methylene blue, water pollutant, catalytic degradation, toxic pollutants, sodium borohydrate, rate constant, Au