A Robust Solution-Based Approach to Monodisperse Hybrid Janus Nanofibers

Monodisperse hybrid Janus nanofibers with the structure that one Au nanoparticle (AuNP) is connected to one end of a polymeric nanofiber were prepared by the self‐assembly between polymeric micelles and the tadpole‐like conjugates resulting from one‐to‐one complexation of long DNA chains with AuNPs.     

Naked-eye detection of amyloid aggregates using gold nanoparticles modified with amyloid beta antibody

We developed a rapid method for estimating the amyloid beta (Aβ)-conformation state related with Alzheimer's disease. We prepared gold nanoparticle (AuNP)-Aβ antibody conjugates treated with bovine serum albumin to stabilize their dispersibility in a buffer. The prepared AuNPs were precipitated in the presence of Aβ aggregates, such as oligomers and fibrils. Aβ monomers did not precipitate AuNPs. The formation of AuNP precipitates by Aβ aggregates could be confirmed by the naked eye within 1 h.     

Transfer of Two‐Dimensional Oligonucleotide Patterns onto Stereocontrolled Plasmonic Nanostructures through DNA‐Origami‐Based Nanoimprinting Lithography

The precise functionalization of self‐assembled nanostructures with spatial and stereocontrol is a major objective of nanotechnology and holds great promise for many applications. Herein, the nanoscale addressability of DNA origami was exploited to develop a precise copy‐machine‐like platform that can transfer two‐dimensional oligonucleotide patterns onto the surface of gold nanoparticles (AuNPs) through a deliberately designed toehold‐initiated DNA displacement reaction. This strategy of DNA‐origami‐based nanoimprinting lithography (DONIL) demonstrates high precision in controlling the valence and valence angles of AuNPs. These DNA‐decorated AuNPs act as precursors in the construction of discrete AuNP clusters with desired chirality.     

Designed diblock oligonucleotide for the synthesis of spatially isolated and highly hybridizable functionalization of DNA-gold nanoparticle nanoconjugates

Conjugates of DNA and gold nanoparticles (AuNPs) typically exploit the strong Au-S chemistry to self-assemble thiolated oligonucleotides at AuNPs. However, it remains challenging to precisely control the orientation and conformation of surface-tethered oligonucleotides and finely tune the hybridization ability. We herein report a novel strategy for spatially controlled functionalization of AuNPs with designed diblock oligonucleotides that are free of modifications. We have demonstrated that poly adenine (polyA) can serve as an effective anchoring block for preferential binding with the AuNP surface, and the appended recognition block adopts an upright conformation that favors DNA hybridization. The lateral spacing and surface density of DNA on AuNPs can also be systematically modulated by adjusting the length of the polyA block. Significantly, this diblock oligonucleotide strategy results in DNA-AuNPs nanoconjugates with high and tunable hybridization ability, which form the basis of a rapid plasmonic DNA sensor.     

Facile, rapid and efficient biofabrication of gold nanoparticles decorated with functional proteins

We report a one-pot biological approach to fabricate gold nanoparticle (AuNP)-ZZ domain conjugates using peptide-functionalized proteins that can simultaneously direct both biomineralization and surface modification of AuNPs. In addition, immuno-AuNPs are readily prepared through the specific binding of antibodies to the ZZ domain on the AuNPs.     

A Spatially Programmable DNA Nanorobot Arm to Modulate Anisotropic Gold Nanoparticle Assembly by Enzymatic Excision

Programmable assembly of gold nanoparticle superstructures with precise spatial arrangement has drawn much attention for their unique characteristics in plasmonics and biomedicine. Bio-inspired methods have already provided programmable, molecular approaches to direct AuNP assemblies using biopolymers. The existing methods, however, predominantly use DNA as scaffolds to directly guide the AuNP interactions to produce intended superstructures. New paradigms for regulating AuNP assembly will greatly enrich the toolbox for DNA-directed AuNP manipulation and fabrication. Here, we developed a strategy of using a spatially programmable enzymatic nanorobot arm to modulate anisotropic DNA surface modifications and assembly of AuNPs. Through spatial controls of the proximity of the reactants, the locations of the modifications were precisely regulated. We demonstrated the control of the modifications on a single 15 nm AuNP, as well as on a rectangular DNA origami platform, to direct unique anisotropic AuNP assemblies. This method adds an alternative enzymatic manipulation to DNA-directed AuNP superstructure assembly.     

Gold‐Nanoparticle‐Mediated Jigsaw‐Puzzle‐like Assembly of Supersized Plasmonic DNA Origami

DNA origami has rapidly emerged as a powerful and programmable method to construct functional nanostructures. However, the size limitation of approximately 100 nm in classic DNA origami hampers its plasmonic applications. Herein, we report a jigsaw‐puzzle‐like assembly strategy mediated by gold nanoparticles (AuNPs) to break the size limitation of DNA origami. We demonstrated that oligonucleotide‐functionalized AuNPs function as universal joint units for the one‐pot assembly of parent DNA origami of triangular shape to form sub‐microscale super‐origami nanostructures. AuNPs anchored at predefined positions of the super‐origami exhibited strong interparticle plasmonic coupling. This AuNP‐mediated strategy offers new opportunities to drive macroscopic self‐assembly and to fabricate well‐defined nanophotonic materials and devices.     

The Electrochemical Behavior of Gold Nanoparticle‐Tantalum(V) Phthalocyanine Composites: Applications Towards the Electroanalysis of Bisphenol A

The formation of gold nanoparticle (AuNP) composites with tantalum phthalocyanines (TaPc) complexes { 1a and 1b (Figure 1 )} is reported. The TaPc‐AuNPs conjugates were characterised by atomic force microscopy (AFM) and transmission electron microscopy. The AFM analyses show that conjugates of TaPc with AuNPs are more aggregated when compared to AuNPs alone. The conjugates and TaPc complexes were immobilized on a gold electrode by drop and dry method and these were characterized by electrochemical impedance spectroscopy. The charge transfer behaviour of AuNPs was enhanced in the presence of TaPc complexes. All the modified electrodes showed electrocatalytic oxidation of bisphenol A. The limits of detection for complexes 1a and 1 b were 4.78×10^?10 and 2.76×10^?10 mol L^?1, respectively.     

Room-temperature cold-welding of gold nanoparticles for enhancing the electrooxidation of carbon monoxide

A cold-welding strategy is proposed to rapidly join together Au nanoparticles (AuNPs) into two-dimensional continuous structures for enhancing the electrooxidation of carbon monoxide by injecting a mixture of ethanol and tolulene into the bottom of a AuNP solution.     

Improving the sensitivity for DNA sensing based on double-anchored DNA modified gold nanoparticles

DNA modified nanoparticles (AuNPs) are an established and widely used type of nucleotide sensor. We sought to improve the design by applying short rigid DNA duplexes near the surface of the AuNPs forming a so called double-anchored AuNP sensor, and compared it with other conventional DNA modified AuNPs. The improved design exhibited higher assembly efficiency, and consequently increased its sensitivity to target DNA.     

Synchronized assembly of gold nanoparticles driven by a dynamic DNA-fueled molecular machine

A strategy for gold nanoparticle (AuNP) assembly driven by a dynamic DNA-fueled molecular machine is revealed here. In this machine, the aggregation of DNA-functionalized AuNPs is regulated by a series of toehold-mediated strand displacement reactions of DNA. The aggregation rate of the AuNPs can be regulated by controlling the amount of oligonucleotide catalyst. The versatility of the dynamic DNA-fueled molecular machine in the construction of two-component "OR" and "AND" logic gates has been demonstrated. This newly established strategy may find broad potential applications in terms of building up an "interface" that allows the combination of the strand displacement-based characteristic of DNA with the distinct assembly properties of inorganic nanoparticles, ultimately leading to the fabrication of a wide range of complex multicomponent devices and architectures.     

A facile in situ generation of dithiocarbamate ligands for stable gold nanoparticle-oligonucleotide conjugates

Here we demonstrate a facile strategy of preparing gold nanoparticle (AuNP) and DNA conjugates by in situ generation of strong metal affinity capping ligands, dithiocarbamates (DTC) modified oligonucleotides; the conjugates produced are stable at elevated temperature, resistant to ligand displacement and preserve the functionality of the conjugated oligonucleotides.     

Free Energy of Bare and Capped Gold Nanoparticles Permeating through a Lipid Bilayer

Herein, we study the permeation free energy of bare and octane‐thiol‐capped gold nanoparticles (AuNPs) translocating through a lipid membrane. To investigate this, we have pulled the bare and capped AuNPs from bulk water to the membrane interior and estimated the free energy cost. The adsorption of the bare AuNP on the bilayer surface is energetically favorable but further loading inside it requires energy. However, the estimated free‐energy barrier for loading the capped AuNP into the lipid membrane is much higher compared to bare AuNP. We also demonstrate the details of the permeation process of bare and capped AuNPs. Bare AuNP induces the curvature in the lipid membrane whereas capped AuNP creates an opening in the interacting monolayer and get inserted into the membrane. The insertion of capped AuNP induces a partial unzipping of the lipid bilayer, which results in the ordering of the local lipids interacting with the nanoparticle. However, bare AuNP disrupts the lipid membrane by pushing the lipid molecules inside the membrane. We also analyze pore formation due to the insertion of capped AuNP into the membrane, which results in water molecules penetrating the hydrophobic region.     

Instantaneous and quantitative functionalization of gold nanoparticles with thiolated DNA using a pH-assisted and surfactant-free route

The attachment of thiolated DNA to gold nanoparticles (AuNPs) has enabled many landmark works in nanobiotechnology. This conjugate chemistry is typically performed using a salt-aging protocol where, in the presence of an excess amount of DNA, NaCl is gradually added to increase DNA loading over 1-2 days. To functionalize large AuNPs, surfactants need to be used, which may generate difficulties for downstream biological applications. We report herein a novel method using a pH 3.0 citrate buffer to complete the attachment process in a few minutes. More importantly, it allows for quantitative DNA adsorption, eliminating the need to quantify the number of adsorbed DNA and allowing the adsorption of multiple DNAs with different sequences at predetermined ratios. The method has been tested for various DNAs over a wide range of AuNP sizes. Our work suggests a synergistic effect between pH and salt in DNA attachment and reveals the fundamental kinetics of AuNP aggregation versus DNA adsorption, providing a novel means to modulate the interactions between DNA and AuNPs.     

DNA aptamer folding on gold nanoparticles: from colloid chemistry to biosensors

We have investigated the effect of the folding of DNA aptamers on the colloidal stability of gold nanoparticles (AuNPs) to which an aptamer is tethered. On the basis of the studies of two different aptamers (adenosine aptamer and K+ aptamer), we discovered a unique colloidal stabilization effect associated with aptamer folding: AuNPs to which folded aptamer structures are attached are more stable toward salt-induced aggregation than those tethered to unfolded aptamers. This colloidal stabilization effect is more significant when a DNA spacer was incorporated between AuNP and the aptamer or when lower aptamer surface graft densities were used. The conformation that aptamers adopt on the surface appears to be a key factor that determines the relative stability of different AuNPs. Dynamic light scattering experiments revealed that the sizes of AuNPs modified with folded aptamers were larger than those of AuNPs modified with unfolded (but largely collapsed) aptamers in salt solution. From both the electrostatic and steric stabilization points of view, the folded aptamers that are more extended from the surface have a higher stabilization effect on AuNP than the unfolded aptamers. On the basis of this unique phenomenon, colorimetric biosensors have been developed for the detection of adenosine, K+, adenosine deaminase, and its inhibitors. Moreover, distinct AuNP aggregation and redispersion stages can be readily operated by controlling aptamer folding and unfolding states with the addition of adenosine and adenosine deaminase.     

Multianalyte Electrochemical Biosensor Based on Aptamer‐ and Nanoparticle‐Integrated Bio‐Barcode Amplification

In the present work, a signal‐on electrochemical sensing strategy for the simultaneous detection of adenosine and thrombin is developed based on switching structures of aptamers. An Au electrode as the sensing surface is modified with two kinds of thiolated capture probes complementary to the linker DNA that contains either an adenosine aptamer or thrombin aptamer. The capture probes hybridize with their corresponding linker DNA, which has prehybridized with the reporter DNA loaded onto the gold nanoparticles (AuNPs). The AuNP contained two kinds of bio‐barcode DNA: one is complementary to the linker DNA (reporter), whereas the other is not (signal) and is tagged with different metal sulfide nanoparticles. Thus a “sandwich‐type” sensing interface is fabricated for adenosine and thrombin. With the introduction of adenosine and thrombin, the aptamer parts bind with their targets and fold to form the complex structures. As a result, the bio‐barcoded AuNPs are released into solution. The metal sulfide nanoparticles are measured by anodic stripping voltammetry (ASV), and the concentrations of adenosine and thrombin are proportional to the signal of either metal ion. With the dual amplification of the bio‐barcoded AuNP and the preconcentration of metal ions through ASV technology, detection limits as low as 6.6×10^?12 M for adenosine and 1.0×10^?12 M for thrombin are achieved. The sensor exhibits excellent selectivity and detectability in biological samples.     

Polystyrene‐Core–Silica‐Shell Hybrid Particles Containing Gold and Magnetic Nanoparticles

Polystyrene‐core–silica‐shell hybrid particles were synthesized by combining the self‐assembly of nanoparticles and the polymer with a silica coating strategy. The core–shell hybrid particles are composed of gold‐nanoparticle‐decorated polystyrene (PS‐AuNP) colloids as the core and silica particles as the shell. PS‐AuNP colloids were generated by the self‐assembly of the PS‐grafted AuNPs. The silica coating improved the thermal stability and dispersibility of the AuNPs. By removing the “free” PS of the core, hollow particles with a hydrophobic cage having a AuNP corona and an inert silica shell were obtained. Also, Fe₃O₄ nanoparticles were encapsulated in the core, which resulted in magnetic core–shell hybrid particles by the same strategy. These particles have potential applications in biomolecular separation and high‐temperature catalysis and as nanoreactors.     

Hybridization chain reaction triggered controllable one-dimensional assembly of gold nanoparticles

Assembling and ordering nanomaterials into desirable patterns are considerably significant, since the properties of nanomaterials depend not only on the size and shape, but also on the spatial arrangement among the collective building blocks. In this work, the DNA self-assembly technology of hybridization chain reaction (HCR) provided a convenient method to yield long double-strand DNA (dsDNA) to install gold nanoparticles (AuNPs) into one dimensional assembly along the skeleton of dsDNA. Interestingly, the tunable length of AuNPs assemblies along dsDNA chain could be achieved by adjusting the reaction time of HCR, which is based on the formation of covalent bond between Au and the -SH group of DNA. Compared with weak light scattering of single AuNP, these AuNPs assemblies could be clearly imaged under the dark field microscopy, indicating that the light scattering was greatly improved after assembling.     

Quantification of ligand packing density on gold nanoparticles using ICP-OES

In this study, a prototypical thiolated organic ligand, 3-mercaptopropionic acid (MPA), was conjugated on gold nanoparticles (AuNPs), and packing density was measured on an ensemble-averaged basis using inductively coupled plasma optical emission spectrometry. The effects of sample preparation, including centrifugation and digestion, as well as AuNP size and concentration, on recovery were investigated. For AuNPs with diameters of 5, 10, 30, 60, and 100 nm, calculated packing density is independent of size, averaging 7.8 nm⁻² and ranging from 6.7 to 9.0 nm⁻², and is comparable to reported values for MPA and similar short-chain ligands on AuNPs. These preliminary data provide fundamental information on the advantages and limitations of ICP-based analyses of conjugated AuNP systems. Moreover, they provide necessary information for the development of more broadly applicable methods for quantifying nanoparticle–ligand conjugates of critical importance to nanomedicine applications.