Hybrid Gold Research Articles

Amyloid fibrils enhance transport of metal nanoparticles in living cells and induced cytotoxicity.

Amyloid protein fibrils occur in vivo as pathological agents, in the case of neurodegenerative diseases, or as functional amyloids, when playing biologically vital roles. Here we show how amyloid fibrils generated from a food protein, β-lactoglobulin, can be used as nanoreactors for the synthesis of metal nanoparticles and demonstrate that the resulting hybrids can play a central role in the internalization of nanoparticles into living cells, with up to 3-fold-enhanced transport properties over pristine nanoparticles. We conjugate gold, silver, and palladium nanoparticles onto amyloid fibrils by chemical reduction, and we study their effect on dendritic and MCF7 breast cancer cells. Transmission electron microscopy indicates localization of nanoparticles inside vesicles of the cells. Flow cytometry reveals that silver nanoparticle-amyloid hybrids are cytotoxic, while gold and palladium nanoparticle-amyloid hybrids produce no notable effect on cell viability and activation status.

One-step synthesis of collagen hybrid gold nanoparticles and formation on Egyptian-like gold-plated archaeological ivory.

A one-step method is reported to synthesize hybrid gold nanoparticles (AuNPs) by reduction of HAuCl4 in acetic solution in the presence of collagen (Col), dicarboxylic acid-terminated polyethylene glycol (PEG), and cetyltetrammonium bromide (CTAB) mixed with hydoxyapatite (HAP) as surfactants. Such formation process of AuNPs was shown to be responsible for purple stains naturally formed on Egyptianizing archaeological gilded ivories from 8th BC Syria. The understanding of this formation mechanism, which most likely involves a step with hybrid AuNPs, allows the establishing of an authenticity marker of ancient gold-plated ivories.

One‐Step Synthesis of Collagen Hybrid Gold Nanoparticles and Formation on Egyptian‐like Gold‐Plated Archaeological Ivory

AbstractA one‐step method is reported to synthesize hybrid gold nanoparticles (AuNPs) by reduction of HAuCl4 in acetic solution in the presence of collagen (Col), dicarboxylic acid‐terminated polyethylene glycol (PEG), and cetyltetrammonium bromide (CTAB) mixed with hydoxyapatite (HAP) as surfactants. Such formation process of AuNPs was shown to be responsible for purple stains naturally formed on Egyptianizing archaeological gilded ivories from 8th BC Syria. The understanding of this formation mechanism, which most likely involves a step with hybrid AuNPs, allows the establishing of an authenticity marker of ancient gold‐plated ivories.

Tuning the shape and size of hybrid gold nanoparticles by porphyrins using seed-mediated synthesis

We report the synthesis of hybrid gold nanostructures by means of seed/growth approach, using porphyrin molecules (protoporphyrin IX) in addition to cetyltetraammonium bromide (CTAB) as surfactants and/or shape-modulating agents. The combination of CTAB and porphyrin yields stable complexes that act as co-directing agents and favor the anisotropic growth of gold nanostructures. Our results revealed the ability of porphyrins to tune the shape and size of gold nanostructures, leading to the formation of a variety of hybrid nano-objects, including bones, thorns, polyhedral and stars.

Optical chemosensors for Hg2+from terthiophene appended rhodamine derivatives: FRET based molecular and in situ hybrid gold nanoparticle sensors

A multifunction sensor based on rhodamine B with a terthiophene substituent has been developed as a highly sensitive chemosensor for Hg2+. This method is mainly based on Hg2+-induced spirocycle opening leading to fluorescence and colorimetric enhancement. The binding properties of a terthiophene appended rhodamine based fluorescence chemosensor (RhoT) was studied using the fluorescence resonance energy transfer (FRET) process, and RhoT displayed highly selective fluorescence enhancement and a color change in the presence of Hg2+. Moreover, the in situ formation of gold nanoparticle/conducting polymer nanocomposite based-chemosensors (AuNPs-RhoT) was achieved to explore the sensitive and selective detection of Hg2+ in aqueous solution over 12 other metal ions using a colorimetric technique. The hybrid sensor became aggregated in solution in the presence of Hg2+ by an ion-templated chelation process, which caused an easily measurable change in the emission spectrum of the particles and provided an inherently sensitive method for Hg2+ detection in aqueous solution.

Relay Catalytic Cascade Hydrosiloxylation and Asymmetric Hetero-Diels–Alder Reaction

The hybrid gold(I)/Bronsted acid binary catalyst system enables enynes to participate in an asymmetric relay catalytic cascade intramolecular hydrosiloxylation and asymmetric hetero-Diels–Alder reaction with fluorenyl glyoxylate.

Formation of hybrid gold nanoparticle network aggregates by specific host-guest interactions in a turbulent flow reactor.

A multi-inlet vortex mixer (MIVM) was used to investigate the formation of hybrid gold nanoparticle network aggregates under highly turbulent flow conditions. To form aggregates, gold nanoparticles were functionalized with β-cyclodextrin (CD) and mixed with adamantyl (Ad)-terminated poly(propyleneimine) dendrimers. Adamantyl-terminated poly(ethylene glycol) was added as a stabilizer to cap the supramolecular aggregates and to provide steric repulsion. Aggregates were characterized using dynamic light scattering, UV-vis spectroscopy, and transmission electron microscopy. It was demonstrated that the growth of the aggregates is driven by specific host-guest interactions between CD and Ad moieties. The size of the supramolecular gold aggregates (20-1000 nm) was controlled by varying the ratio of the Ad and CD concentrations. The turbulent flow was found to have a minor effect on the supramolecular aggregate size at relatively low Ad/CD ratios, whereas it had a substantial effect at high Ad/CD ratios, leading to larger agglomerates in solution compared to laminar flow and manual conditions.

Plasmonic bipyramids for fluorescence enhancement and protection against photobleaching

A great number of studies focus their interest on the photophysical properties of fluorescent hybrid gold nanoparticles for potential applications in biotechnologies such as imaging and/or treatment. Spherical gold nanoparticles are known to quench a chromophore fluorescent signal, when moieties are located in their close vicinity. The use of a polymer spacer on such a system allowed only partial recovery of the dye emission by controlling the surface to dye distance. Gold-based anisotropic sharp nanostructures appear to exhibit more interesting features due to the strong electric field generated at their edges and tips. In this paper, a complete study of hybrid fluorescent bipyramidal-like gold nanostructures is presented. We describe the chemical synthesis of gold bipyramids functionalized with fluorescent water-soluble polymers and their photophysics both in solution and on a single object. We show that the use of a bipyramidal shape instead of a spherical one leads to total recovery of the fluorescence and even to an enhancement of the emission of the dyes by a factor of 1.4.

Layer-by-Layer synthesis and tunable optical properties of hybrid magnetic–plasmonic nanocomposites using short bifunctional molecular linkers

Spurred by research in magnetoplasmonics, plasmon-enhanced magneto-optical effects and active plasmonics, the demand for hybrid magnetic–plasmonic nanoparticle-based materials of optical quality is high. Currently used synthesis methods involve possibly interfering polymer media or polyelectrolyte interlayers, grooved supports or non-transparent substrates. To obtain homogeneous, partially transparent and polymer/polyelectrolyte-free magnetic–plasmonic nanocomposites with angle-independent optical properties, we produced hybrid gold–magnetite and silver–magnetite nanocomposites by a novel Layer-by-Layer synthesis using short bifunctional molecular linkers on glass substrates. Resulting nanocomposites had high nanoparticle filling fractions and showed tunability of the plasmon wavelength over a very broad spectral range by changing composite thickness through the number of added nanoparticle layers. The angle-independence of optical properties and the abilities to switch the plasmonic material and to tune the plasmon resonances of the magnetic–plasmonic composites make these materials a unique platform for magnetoplasmonic research.

Electrografting of N’,N’-dimethylphenothiazin-5-ium-3,7-diamine (Azure A) diazonium salt forming electrocatalytic organic films on gold or graphene oxide gold hybrid electrodes

Electroactive films containing redox active phenothiazine moieties are covalently bound onto gold and graphene oxide gold hybrid electrodes, using reductive redox grafting of N’,N’-dimethylphenothiazin-5-ium-3,7-diamine (Azure A) diazonium salt. The grafting procedure is based on continuous voltammetric potential sweep of solutions containing the phenothiazine diazonium salt previously generated in situ. Control of the film thickness, electroactivity and stability can easily be exerted through appropriate choice of the concentration and number of potential scans performed. Cyclic Voltammetry, Electrochemical Quartz Crystal Microbalance (EQCM) and Spectroscopic Ellipsometry are used to characterize the growth process as well as the viscoelastic properties of the resulting stable electrografted films. The electron transfer reactions through the films are mediated by the presence of the Azure A redox moieties, which show a quasi-reversible electrochemical response and exhibit a potent electrocatalytic effect toward the oxidation of NADH. This electrocatalytic model has been used to compare the properties of Azure A electrografted films generated on gold electrodes with those obtained on hybrid electrodes composed by graphene oxide modified gold electrodes.

Multiresponsive Block Copolymer‐Modified “Hairy” Gold Nanoparticles for Remote Control of Interfaces

Hybrid gold nanoparticles modified with poly(N‐isopropylacrylamide)‐block‐poly(2‐succinyloxyethyl methacrylate) (PNIPAM‐b‐PSEMA) brushes are synthesized using surface‐initiated atom transfer radical polymerization (SI‐ATRP). The “hairy” particles demonstrate reversible pH‐ and temperature‐controlled changes in size and aggregation state in solution. When adsorbed within a sub‐monolayer at a solid surface, they support reversible changes in surface wettability in response to changes in solution pH, temperature, or illumination by laser light.

Tuning Dye-to-Particle Interactions toward Luminescent Gold Nanostars

Light-matter interactions are of great interest for potential biological applications (bioimaging, biosensing, phototherapy). For such applications, sharp nanostructures exhibit interesting features since their extinction bands (surface plasmon resonance) cover a large bandwidth in the whole visible wavelength region due to the existence of "hot spots" located at the end of the tips. In this context, gold nanostars appear to be interesting objects. However, their study remains difficult, mainly due to complicated synthetic methods and further functionalization. This paper reports the synthesis, functionalization, and photophysics of luminescent hybrid gold nanostars prepared using a layer-by-layer (LbL) deposition method for the tuning of chromophore-to-particle distances together with the impact of the spectral overlap between the plasmon and the emission/absorption of the dyes. Several luminescent dyes with different optical signatures were selectively adsorbed at the nanoparticle surface. The optimized systems, exhibiting the highest luminescence recovery, clearly showed that overlap must be as low as possible. Also, the fluorescence intensities were quenched in close vicinity of the metal surface and revealed a distance-dependence with almost full recovery of the dyes emission for 11 LbL layers, which corresponded to 15 nm distances evaluated on dried samples. The photophysics of the luminescent core-shell particles were carried out in suspension and correlated with the response of isolated single objects.

Worldwide open access: UK leadership?

The web is destined to become humankind's cognitive commons, where digital knowledge is jointly created and freely shared. The UK has been a leader in the global movement toward open access (OA) to research but recently its leadership has been derailed by the joint influence of the publishing industry lobby from without and well-intentioned but premature and unhelpful over-reaching from within the OA movement itself. The result has been the extremely counterproductive ‘Finch Report’ followed by a new draft of the Research Councils UK (RCUK) OA mandate, downgrading the role of cost-free OA self-archiving of research publications (‘green OA’) in favor of paying subscription publishers over and above subscriptions, out of scarce research funds, in exchange for making single articles OA (‘hybrid gold OA’). The motivation of the new policy is to reform publication and to gain certain re-use rights (CC-BY), but the likely effect would be researcher resistance, very little OA and a waste of research funds. There is still time to fix the RCUK mandate and restore the UK's leadership by taking a few very specific steps to clarify and strengthen the green component by adding a mechanism for monitoring and verifying compliance, with consequences for non-compliance, along lines also being adopted in the EC and the US.

Control of Gold Nanoparticle Superlattice Properties via Mesogenic Ligand Architecture

Hybrid structures made of metal nanoparticles with liquid crystalline coating attract considerable attention due to their conspicuous self-assembly and potential synergistic properties. Here we report on a new structural parameter that can be used to control the formation of hybrid gold nanoparticles superlattice. A series of Au nanoclusters covered with mixed monolayers of alkyl and liquid-crystalline ligands were obtained. For the first time in such systems the lengths of both alkyl ligands and mercapto-functionalized alkyl spacers of the promesogenic molecules were varied. The physicochemical properties of the obtained materials were investigated by different instrumental techniques, such as X-ray photoelectron spectroscopy (XPS), small-angle X-ray diffraction (SAXRD), and transmission electron microscopy (TEM). Interestingly, the applied variations of the grafting layer composition enabled the formation of 1D (lamellar) and 3D long-range ordered structures with systematically changing thermal stability range. Such behavior is explained based on the structural parameters of the hybrid nanoparticles, namely the separation of the cores and ligand flexibility. This work gives some new insights into the nanoparticle self-assembly subject and points out the critical parameters controlling the degree of order within the self-assembled superstructures.

Macroscopic Polarized Emission from Aligned Hybrid Gold Nanorods Embedded in a Polyvinyl Alcohol Film

Macroscopic polarized emission is realized from aligned hybrid gold nanorods (HGNRs) embedded in a polyvinyl alcohol film. The alignment of HGNRs is achieved by employing a film stretch method. Under a circularly polarized pump, the emission polarization of the stretched film shows a dipole-like pattern while the original film shows an isotropic emission polarization.

Nanogold-enhanced graphene nanosheets as multienzyme assembly for sensitive detection of low-abundanceproteins

A new electrochemical immunosensing protocol was designed for detection of carcinoembryonic antigen (CEA, as a model protein) by using graphene-carried poly(o-phenylenediamine)/gold hybrid nanosheets (GNPGs) as signal tags on the hierarchical dendritic gold microstructures (HDGMs)-modified glassy carbon electrode. To prepare the signal tags, poly(o-phenylenediamine) molecules were initially immobilized on the surface of graphene nanosheets via the π-stacking interaction. Then gold nanoparticles were assembled onto the poly(o-phenylenediamine)-modified graphene nanosheets, which were used for the labeling of anti-CEA detection antibodies and horseradish peroxidase (HRP). The as-prepared GNPGs were characterized by using atomic force microscopy (AFM), transmission electron microscopy (TEM) and UV–vis absorption spectroscopy. The assay was carried out with a sandwich-type immunoassay format in pH 5.5acetic acid-buffered saline solutions containing 2.5mmolL−1 H2O2. Under optimal conditions, the electrochemical immunoassay exhibited a wide dynamic range of 0.005–80ngmL−1 toward CEA standards with a low detection limit of 5.0pgmL−1. Intra- and inter-assay coefficients of variation were less than 11.5%. No significant difference at the 0.05 significance level was encountered in the analysis of 6clinical serum specimens and 6spiked blank new born cattle serum specimens between the developed immunoassay and commercially available electrochemiluminescent (ECL) method for the detection ofCEA.

Medical Physics becomes a hybrid gold open‐access journal

<i>Medical Physics</i> becomes a hybrid gold open‐access journal

Hybrid gold nanocube@silica@graphene-quantum-dot superstructures: synthesis and specific cell surface protein imaging applications

Hybrid AuNCs@SiO2@GQDs nanocomposites were synthesized via a multistep procedure; GQDs located near AuNCs showed enhanced fluorescent intensities and improved photostabilities. AuNCs@SiO2@GQDs nanocomposites allowed specific visualization of EGFR on cancer cells.

A highly oriented hybrid microarray modified electrode fabricated by a template-free method for ultrasensitive electrochemical DNA recognition

Highly oriented growth of a hybrid microarray was realized by a facile template-free method on gold substrates for the first time. The proposed formation mechanism involves an interfacial structure-directing force arising from self-assembled monolayers (SAMs) between gold substrates and hybrid crystals. Different SAMs and variable surface coverage of the assembled molecules play a critical role in the interfacial directing forces and influence the morphologies of hybrid films. A highly oriented hybrid microarray was formed on the highly aligned and vertical SAMs of 1,4-benzenedithiol molecules with rigid backbones, which afforded an intense structure-directing power for the oriented growth of hybrid crystals. Additionally, the density of the microarray could be adjusted by controlling the surface coverage of assembled molecules. Based on the hybrid microarray modified electrode with a large specific area (ca. 10 times its geometrical area), a label-free electrochemical DNA biosensor was constructed for the detection of an oligonucleotide fragment of the avian flu virus H5N1. The DNA biosensor displayed a significantly low detection limit of 5 pM (S/N = 3), a wide linear response from 10 pM to 10 nM, as well as excellent selectivity, good regeneration and high stability. We expect that the proposed template-free method can provide a new reference for the fabrication of a highly oriented hybrid array and the as-prepared microarray modified electrode will be a promising paradigm in constructing highly sensitive and selective biosensors.

Fluorocarbon–hydrocarbon hybrid gold NPs synthesized by bulk exchange reactions and surface coatings of fluorocarbon coated gold NPs are increased

Surface structure of nanoparticles (NPs) has considerable effect on their usability and efficiency in a wide variety of applications such as electronics, photonics, catalysis, chemical sensing, and drug-delivery systems, etc. This turns the surface modification of nanoparticles into a quite important and intriguing issue. Therefore, being able to decorate the surface of NPs with desired ligands and with high surface coverage is becoming more significant day after day. Several agents can be used for the surface decoration. Fluorinated chains are among the most important ones in accordance with having fluidization effect over lipid membranes and being able to be used to manipulate/control the surface interactions. This letter covers enhancing surface coating of fluorocarbon (PFDT; 1H,1H,2H,2H-perfluorodecanethiol) coated gold NPs by modifying a classic synthesis procedure: Brust’s two phase method. Moreover, surface decorated NPs with mixed fluorocarbon (PFDT)-hydrocarbon (DT; 1-Dodecanethiol) ligands were synthesized, and their interfacial and bulk properties were investigated by Thermogravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR), Nuclear Magnetic Resonance Spectroscopy (NMR), Transmission Electron Microscopy (TEM), and utilization of surface pressure-area isotherm data.