AuNP Content Research Articles

Thermo-sensitive Microgels Supported Gold Nanoparticles as Temperature-mediated Catalyst

Microgels with a thermo-sensitive poly(N-isopropylacrylamide) (polyNIPAm) backbone and bis-imidazolium (VIM) ionic cross-links, denoted as poly(NIPAm-co-VIM), were successfully prepared. The as-synthesized ionic microgels were converted to nanoreactors, denoted as Au@PNI MGs, upon generation and immobilization of gold nanoparticles (Au NPs) of 5–8 nm in size into poly(NIPAm-co-VIM). The content of Au NPs in microgels could be regulated by controlling the 1,6-dibromohexane/vinylimidazole molar ratio in the quaternization reaction. The microgel-based nanoreactors were morphologically spherical and uniform in size, and presented reversible thermo-sensitive behavior with volume phase transition temperatures (VPTTs) at 39–40 °C. The Au@PNI MGs were used for the reduction of 4-nitrophenol, of which the catalytic activity could be modulated by temperature.

TiO₂-SiO₂ Coatings with a Low Content of AuNPs for Producing Self-Cleaning Building Materials.

The high pollution levels in our cities are producing a significant increase of dust on buildings. An application of photoactive coatings on building materials can produce buildings with self-cleaning surfaces. In this study, we have developed a simple sol-gel route for producing Au-TiO2/SiO2 photocatalysts with application on buildings. The gold nanoparticles (AuNPs) improved the TiO2 photoactivity under solar radiation because they promoted absorption in the visible range. We varied the content of AuNPs in the sols under study, in order to investigate their effect on self-cleaning properties. The sols obtained were sprayed on a common building stone, producing coatings which adhere firmly to the stone and preserve their aesthetic qualities. We studied the decolourization efficiency of the photocatalysts under study against methylene blue and against soot (a real staining agent for buildings). Finally, we established that the coating with an intermediate Au content presented the best self-cleaning performance, due to the role played by its structure and texture on its photoactivity.

Fabrication and Verification of Conjugated AuNP-Antibody Nanoprobe for Sensitivity Improvement in Electrochemical Biosensors

This study was designed to obtain covalently coupled conjugates as means for achieving higher stability and better coverage of the AuNPs by antibodies on the particle surface suitable for sensor performance enhancement. Starting by using a modified protocol, colloid gold solution, with mean AuNP core size of ~6 nm was synthesized. The protocol used for conjugation of AuNPs to osteocalcin antibody in this study relies on covalent and electrostatic attractions between constituents. Varieties of conjugates with varying combinations of crosslinkers and different concentrations were successfully synthesized. The obtained products were characterized and their properties were studied to determine the best candidate in sense of antibody - antigen reactivity. Using AuNP-GSH-NHS-Ab combination (1:1:1), the tertiary structure of the protein was maintained and thus the antibody remained functional in the future steps. This one-pot method provided a simple method for covalently coupling antibodies on the particle surface while keeping their functionality intact. The AuNP content of the solution also accelerated electron transfer rate and thus amplifies the detection signal. With the developed and discussed technique herein, a simple solution is modeled to be used for measuring serum levels of biomarkers in single and/or multiplexed sensor systems.

An image processing application for quantitative cross-correlative microscopy for large cell-populations: a gold nanoparticle radiosensitisation study

A robust analysis script was developed in MATLAB for cross-correlative quantification of internalised gold nanoparticle (AuNP) uptake in a large number of individual cells with the corresponding number of DNA double-strand breaks (DSBs) in the same cells. The correlation of inorganic NP content with a biological marker at the single-cell level will aid in the elucidation of mechanisms of NP radiosensitisation. PC-3 cells were co-cultured with AuNPs and irradiated using an iridium-192 source. AuNP uptake was measured using synchrotron X-ray fluorescence (XRF) and DSBs imaged via confocal microscopy. MATLAB 2016a was used to develop a script to cross-correlate the two imaging modalities and quantify both DSBs and internalised AuNP content in the same cell. Various user-defined options written into the script give a high degree of versatility, which can account for a large number of variables in experimental parameters and data acquisition. The analysis procedure is flexible and robust, which gives consistent consideration to the wide spectrum of potential input image/data sets. Quantitative correlative microscopy was achieved with a custom MATLAB script used to correlate γH2AX foci (a marker of DNA DSBs) from confocal microscopy with AuNP content acquired using synchrotron XRF at the single-cell level. The script can be extended to a broad range of multi-modality imaging spectroscopies.

Highly active CeO2 hollow-shell spheres with Al doping

Metal oxide hollow structures are of great interest in many current and emerging areas of technology. This paper presents a facile and controlled protocol for the synthesis of Al-doped CeO2 hollow-shell spheres (CHS), where the dopant confers enhanced stability and activity to the material. These Al-doped CeO2 hollow-shell spheres (ACHS) possess a controllable shell number of up to three, where the sizes of the exterior, middle, and interior spheres were about 250‒100 nm,150‒50 nm, and 40‒10 nm, respectively, and the average shell thickness was ~15 nm. The thermal stability of the ACHS structure was enhanced by the homogeneous incorporation of Al atoms, andmore active oxygen species were present compared with those in the non-doped congener. Au NPs supported on ACHS (Au/ACHS) showed superior catalytic performance for the reduction of p-nitrophenol. For the same Au NP content, the reaction rate constant (k) of the Au/ACHS was nearly twice that of the non-doped Au/CHS, indicating that Al doping is promising for improving the performance of inert or unstable oxides as catalyst supports.

Novel bioactive glass-AuNP composites for biomedical applications

The bioactive glasses doped with gold nanoparticles (AuNPs) are very attractive materials due to their potential in medical applications. In the present study Pluronic-nanogold hybrid nanoparticles were introduced during the sol-gel route of the SiO2-CaO-P2O5 glasses preparation. The obtained samples were characterized by UV–vis spectroscopy, X-ray diffraction, FT-IR spectroscopy, transmission electron and scanning electron microscopy and afterwards they were investigated in terms of bioactivity, protein adsorption and cells viability. The in vitro bioactivity assessment shows the increase of the number of agglomerated spherical shapes of apatite layers for all Au containing samples, but apatite like structure sizes are influenced by the AuNP content. Beside the spherical shapes, three-dimensional flower-like nanostructures were observed on the surface of the glass with 0.2mol% Au2O. Zeta potential and fluorescence spectroscopy measurements evidenced that the amount of serum albumin adsorbed onto the composites surface increases with the AuNP content. FT-IR measurements point out that the secondary structure of the adsorbed proteins presents few minor changes, indicating biocompatibility of the AuNP doped glasses. The good proliferation rate of Human keratinocytes cells obtained in the presence of samples with 0.15 and 0.2mol% Au2O is comparable with the values achieved from free AuNP, fact that proves the preservation of AuNP properties after their incorporation inside the bioactive glass matrices.

Fabrication of Light-triggered AuNP/CNC/SMP Nano-Composites

Cellulose, an abundant natural polysaccharide, can be applied to immobilize particles on the surface due to the presence of ample hydroxyl groups. A series of different sizes and contents of gold nanoparticles (AuNP) were prepared on cellulose nanocrystal (CNC). The obtained AuNP/CNC nanocomposites were then blended with shape-memory polyurethane (SMP) to prepare light-triggered AuNP/CNC/SMP nanocomposites through solvent conversion and a solution casting method. The nanocomposite films were endowed with higher mechanical properties and striking remote-control light-triggered shape-memory properties. Moreover, the CNC in the composites also enhanced the photothermal effect of AuNPs by preventing the aggregation of AuNPs. At the same time, the content of AuNPs with existing CNC had a stronger effect on the elevated temperature (∆T) and the shape-memory properties of films in comparison to the size of the AuNPs.

Heat Dissipation of Resonant Absorption in Metal Nanoparticle-Polymer Films Described at Particle Separation Near Resonant Wavelength

Polymer films containing plasmonic nanostructures are of increasing interest for development of responsive energy, sensing, and therapeutic systems. The present work evaluates heat dissipated from power absorbed by resonant gold (Au) nanoparticles (NP) with negligible Rayleigh scattering cross sections randomly dispersed in polydimethylsiloxane (PDMS) films. Finite element analysis (FEA) of heat transport was coordinated with characterization of resonant absorption by Mie theory and coupled dipole approximation (CDA). At AuNP particle separation greater than resonant wavelength, correspondence was observed between measured and CDA-predicted optical absorption and FEA-derived power dissipation. At AuNP particle separation less than resonant wavelength, measured extinction increased relative to predicted values, while FEA-derived power dissipation remained comparable to CDA-predicted power absorption before lagging observed extinguished power at higher AuNP content and resulting particle separation. Effects of isolated particles, for example, scattering, and particle-particle interactions, for example, multiple scattering, aggregation on observed optothermal activity were evaluated. These complementary approaches to distinguish contributions to resonant heat dissipation from isolated particle absorption and interparticle interactions support design and adaptive control of thermoplasmonic materials for a variety of implementations.

Assessing the Intracellular Integrity of Phosphine-Stabilized Ultrasmall Cytotoxic Gold Nanoparticles Enabled by Fluorescence Labeling.

As the size of nanoparticles (NPs) is in the range of biological molecules and subcellular structures, they provide new perspectives in biomedicine. This work presents studies concerning the cellular uptake and distribution of phosphine-stabilized cytotoxic 1.4 nm sized AuNPs and their probable degradation during this process. Therefore, ultrasmall phosphine-stabilized AuNPs are modified by linking a fluorophore covalently to the ligand shell. Monitoring the fluorescence on a cellular level by means of flow cytometry and confocal laser scanning microscopy allows determining the fate of the ligand shell during AuNP cell internalization, due to the fact that the fluorescence of a fluorophore bound near to the AuNP surface is quenched. Cell fractionation is conducted in order to quantify the AuNP content at the cell membrane, in the cytoplasm, and the cell nucleus. The incubation of cells with the fluorophore-modified AuNPs reveals a partial loss of the ligand shell upon AuNP cell interaction, evident by the emerging fluorescence signal. This loss is the precondition to unfold high AuNP cytotoxicity. Together with their significantly different biodistribution and enhanced circulation times compared to larger AuNPs, the findings demonstrate the high potential of ultrasmall AuNPs for drug development or therapy.

Liquid Surface X-ray Studies of Gold Nanoparticle-Phospholipid Films at the Air/Water Interface.

Amphiphilic phospholipids and nanoparticles functionalized with hydrophobic capping ligands have been extensively investigated for their capacity to self-assemble into Langmuir monolayers at the air/water interface. However, understanding of composite films consisting of both nanoparticles and phospholipids, and by extension, the complex interactions arising between nanomaterials and biological membranes, remains limited. In this work, dodecanethiol-capped gold nanoparticles (Au-NPs) with an average core diameter of 6 nm were incorporated into 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayers with surface densities ranging from 0.1 to 20% area coverage at a surface pressure of 30 mN/m. High resolution liquid surface X-ray scattering studies revealed a phase separation of the DPPC and Au-NP components of the composite film, as confirmed with atomic force microscopy after the film was transferred to a substrate. At low Au-NP content, the structural organization of the phase-separated film is best described as a DPPC film containing isolated islands of Au-NPs. However, increasing the Au-NP content beyond 5% area coverage transforms the structural organization of the composite film to a long-range interconnected network of Au-NP strands surrounding small seas of DPPC, where the density of the Au-NP network increases with increasing Au-NP content. The observed phase separation and structural organization of the phospholipid and nanoparticle components in these Langmuir monolayers are useful for understanding interactions of nanoparticles with biological membranes.

Photothermally induced scratch healing effects of thermoplastic nanocomposites with gold nanoparticles

A novel method for providing thermoplastic coatings with light-triggered self-healing ability is reported. Normal thermoplastic coatings can be healed efficiently via local heating generated by photothermal effect of gold nanoparticles (Au NPs). Small amounts of Au NPs were successfully dispersed into the coatings. Once the scratch occurred in the coating surface, a laser could be used to illuminate Au NPs to generate a large amount of heat which dramatically increased the local temperature through the photothermal effect. It would melt the polymer and form local deformation to merge the scratch efficiently. It had been confirmed that the coating containing Au NPs had the healing ability. After healing, the surface morphology and the mechanical property were recovered. The mechanism of the healing was also investigated and it was found that the Au NPs content and irradiation intensity played the key roles in the healing process. Through adjusting these two elements, the maximum temperature rise could achieve 225.5 °C. Healing tests were carried out on multiple types of thermoplastic coatings (PAA, PVAc, PS and TPU) and repeated healing was also achieved.

An in vivo study of the biodistribution of gold nanoparticles after intervaginal space injection in the tarsal tunnel

The biodistribution of gold nanoparticles (AuNPs) is closely related to toxicological effects and is of great concern because of their potential application in diverse biomedical areas. However, with the discovery of novel anatomic and histological structures for fluid transport, the underlying mechanisms involved in the in vivo transport and biodistribution of AuNPs require further in-depth investigations. In the current study, we investigated the biodistribution of 10-nm AuNPs in rats after intervaginal space injection (ISI) in the tarsal tunnel, where a focal point of tendons, vessels, and nerve fibers may optimally connect to other remote connective tissues. The intravenous injection (IVI) of AuNPs served as a control. The blood and organs were collected at 5, 15, and 30 min and at 1, 4, 12, and 24 h after injection for quantitative analysis of Au distribution with inductively coupled plasma mass spectrometry (ICP-MS). IVI and ISI yielded significantly different results: The AuNP content in the blood after ISI was much lower than that after IVI; was similar in the lungs, heart, and intestines; and was higher in the skin and muscle. These findings were supported by the ratios of AuNP content and relative organ AuNP distribution proportions. Our results demonstrated a fast, direct, and the circulation-independent AuNP–organ transport pathway, which may improve our understanding of physiological and pathological biodistribution processes in biological systems. Furthermore, these results provide novel insights into the in vivo transport and biodistribution of AuNPs, which may lead to novel and efficient therapeutic and administration strategies.

Controlled assembly of one-dimensional MoO3@Au hybrid nanostructures as SERS substrates for sensitive melamine detection

A new, feasible, and highly efficient platform was developed using self-assembly of (3-aminopropyl) diethoxymethylsilane (ATES) to create metallic oxide-based noble metal nanoparticle hybrid materials. The ex situ approach for fabricating 1D MoO3-nanowires (MoO3-NWs) or ZnO-nanorods (ZnO-NRs) @Au-nanoparticles (Au-NPs) hybrid surface-enhanced Raman scattering (SERS) substrates not only provides a simple route for the decoration of noble metal nanoparticle on metallic oxide nanomaterials, but also realizes the controllable assembly/co-assembly of pre-synthesized nanoparticles with distinctively different sizes, compositions, shapes, and properties. Control over the self-assembly synthesis for morphology and SERS activity was demonstrated by several parameters: (i) coupling agent of ATES, (ii) ATES content, (iii) Au-NPs content, (iv) Au-NP sizes, and (v) other metallic oxide such as ZnO-NRs. The finite difference time domain (FDTD) method was employed to visualize the enhancement mechanism distribution of the hybrid substrate. Furthermore, the optimized MoO3-NW@Au-NPs SERS substrate manifests high SERS sensitivity to melamine with a limit of detection (LOD) of 0.1 ppb (0.08 nM) and excellent uniformity (RSD = 9.26%). The LOD was much lower than the maximal residue limit (MRL) of 2.5 ppm in food prescribed by the US Food and Drug Administration (FDA).

Synthesis and optoelectronics properties of diblock copolymer of P3HT containing thiol-side chains and its hybrid nanocomposite

DP-P3HT-SH in global, leaf-like and elliptical shape states exhibiting broad absorption spectra between 300 nm and 650 nm, and the conductivity values of a DP-P3HT-S-AuNPs hybrid nanoparticle film as a function of the weight content of AuNPs.

Au@NaYF4:Tb3+ core@shell nanostructures: Synthesis and construction of luminescence resonance energy transfer

Luminescence resonance energy transfer (LRET) system can be constructed using NaYF4:Tb3+ luminescence nanocrystals and gold nanoparticles (AuNPs) served as energy donor and acceptor, respectively. The AuNPs modified by cetyltrimethylammonium bromide (CTAB) were synthesized first and NaYF4:Tb3+ shells encapsulated Au cores via a hydrothermal method. The synthesized materials were well characterized by X-ray diffraction (XRD), Fourier-transform infrared spectra (FT-IR), Transmission electron microscopy (TEM), X-ray photoelectron spectrum (XPS), UV–vis absorption spectra (UV–vis) and photoluminescence (PL) measurement. The results indicate that the synthesized Au@NaYF4:Tb3+ core–shell nanoparticles have spherical morphology with a size of 80–90nm and the shell layers of NaYF4:Tb3+ nanocrystals have pure cubic structure. The luminescence properties of Au@NaYF4:Tb3+ core–shell nanoparticles are same as those of NaYF4:Tb3+ particles. The LRET process was realized using the core–shell nanoarchitectures due to the absorption spectrum of AuNPs matches well with the major emission peaks of Tb3+ ions. The LRET experiments have successfully verified the energy transfer between NaYF4:Tb3+ nanocrystals and AuNPs. Additionally, the emission intensities of Tb3+ ions and the content of AuNPs exhibited a fair linear correlation.

Trafficking of Gold Nanoparticles Coated with the 8D3 Anti-Transferrin Receptor Antibody at the Mouse Blood-Brain Barrier.

Receptor-mediated transcytosis has been widely studied as a possible strategy to transport neurotherapeutics across the blood-brain barrier (BBB). Monoclonal antibodies directed against the transferrin receptor (TfR) have been proposed as potential carrier candidates. A better understanding of the mechanisms involved in their cellular uptake and intracellular trafficking is required and could critically contribute to the improvement of delivery methods. Accordingly, we studied here the trafficking of gold nanoparticles (AuNPs) coated with the 8D3 anti-transferrin receptor antibody at the mouse BBB. 8D3-AuNPs were intravenously administered to mice and allowed to recirculate for a range of times, from 10 min to 24 h, before brain extraction and analysis by transmission electron microscope techniques. Our results indicated a TfR-mediated and clathrin-dependent internalization process by which 8D3-AuNPs internalize individually in vesicles. These vesicles then follow at least two different routes. On one hand, most vesicles enter intracellular processes of vesicular fusion and rearrangement in which the AuNPs end up accumulating in late endosomes, multivesicular bodies or lysosomes, which present a high AuNP content. On the other hand, a small percentage of the vesicles follow a different route in which they fuse with the abluminal membrane and open to the basal membrane. In these cases, the 8D3-AuNPs remain attached to the abluminal membrane, which suggests an endosomal escape, but not dissociation from TfR. Altogether, although receptor-mediated transport continues to be one of the most promising strategies to overcome the BBB, different optimization approaches need to be developed for efficient drug delivery.

Metal-enhanced fluorescence effect of Ag and Au nanoparticles modified with rhodamine derivative in detecting Hg2+

In this study, two metal-enhanced fluorescence chemosensors, metal mesoporous materials (hexagonal mesoporous silica (HMS) material loading with Ag and Au NPs were defined as Ag-HMS and Au-HMS) functionalized by rhodamine derivative R, have been prepared by a simple and effective impregnation–reduction method and used for Hg2+ detection in aqueous media. These materials were characterized by transmission electron microscopy (TEM), N2 physical adsorption–desorption, X-ray powder diffraction (XRD), UV–Vis spectrum and Fourier transform infrared spectroscopy (FT-IR). Both HMS-Ag-R and HMS-Au-R chemosensors have high selectivity toward Hg2+ in presence of interfering ions. According to the results, the suitable content of Ag and Au NPs is 2 wt% in the metal nanocomposite Ag-HMS and Au-HMS, respectively. In this paper, HMS-Ag-R shows a higher enhancement factor (EF) of 4.58 comparing with HMS-Au-R (EF = 2.93) in presence of 100 ppb Hg2+. The detection limits of HMS-Ag-R and HMS-Au-R for Hg2+ were determined as 0.9 and 1.4 ppb, respectively. Furthermore, the fluorescence lifetime of R reduced slightly after introducing Ag and Au NPs, and the localized surface plasmon resonance spectra of Ag and Au NPs all exhibited blueshift after immobiling rhodamine derivative R. It can be concluded that the metal-enhanced fluorescence effect of Ag-HMS is more powerful than Au-HMS.

Preparation and Photocatalytic Activity of Gold Nanoparticles (AuNPs)/ZnFe<sub>2</sub>O<sub>4</sub>

Gold nanoparticles (AuNPs)/ZnFe2O4 nanocomposites were prepared by a colloidal deposition (CD) method. The as-prepared AuNPs/ZnFe2O4 nanocomposites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy dispersive spectrum (EDS). XRD results showed that the diffraction peaks of AuNPs gradually increased with the increase of AuNPs content. SEM observations revealed that the AuNPs were presented as regular nanoparticles on the ZnFe2O4 in all the composites. With the increase in Au content, the amount of AuNPs deposited on ZnFe2O4 surface increased. EDS element analysis indicated that the actual content of AuNPs in nanocomposites was consistent with its preset value before preparation by CD method. An active dye, Methyl Orange (MO), was employed as the target pollutant to evaluate the photocatalytic activity of AuNPs/ZnFe2O4 under UV irradiation. The photocatalytic evaluation showed that MO discoloration ratio could reach 72.17% when the nanocomposite with AuNPs content of 5 wt.% was used as the photocatalyst. Finally, the possible mechanism for the enhanced photocatalytic activity of ZnFe2O4 by AuNPs was proposed.

Site-selective immobilization of gold nanoparticles on graphene sheets and its electrochemical properties

Abstract The site-selective attachment of metal nanoparticles (NPs) on graphene surface is highly desirable for various applications such as electrochemical sensors and catalysts. Here, we present a simple and effective synthetic approach for the site-selective immobilization of gold NPs (AuNPs) on either basal planes or edges of graphene sheets. The basic principle of this approach is to use cyteamine linker with reactive amine and thiol functional groups at each end, where the amine groups at one end covalently bind to functional groups presented on edges and/or basal planes of chemically synthesized graphene sheets, and the thiol groups at the other end assemble onto pre-synthesized AuNPs through thiol-Au interaction. Due to the difference in the spatial distribution of functional groups presented on graphene oxide (GO) and reduced graphene oxide (rGO) sheets, most of AuNPs are homogeneously immobilized on the basal planes of the cysteamine-functionalized graphene oxide (GO-SH) sheets, whereas AuNPs are selectively attached at the edge parts of the cysteamine-functionalized reduced graphene oxide (rGO-SH) sheets. Raman signals of GO-SH/Au hybrid films with the high content of AuNPs in the hybrids are clearly increased owing to the formation of the charge-transfer complex between AuNPs and GO-SH sheets, exhibiting surface-enhanced Raman scattering (SERS) activity. Furthermore, rGO-SH/Au hybrids enhance the electrochemical activity of modified glassy carbon electrodes owing to the synergetic effects of electrical conduction by the restored aromatic structure of rGO sheets and percolated network of AuNPs along the graphene edges

In Situ Formation of Polymer-Gold Composite Nanoparticles with Tunable Morphologies.

A simple and efficient route to gold-polymer nanoparticle composites is described. Our versatile synthetic route exerts facile control over polymer nanoparticle morphology, including micelles, rod-like structures, and vesicles, all easily attainable from a single polymerization taken to different monomer conversions. Specifically, poly[oligo(ethylene glycol) methacrylate]-b-poly(dimethylaminoethyl methacrylate)-b-poly(styrene) (POEGMA-b-PDMAEMA-b-PST) triblock copolymers were synthesized using a polymerization induced self-assembly (PISA) approach. Subsequently, spherical gold nanoparticles (10 nm AuNPs) were formed at the hydrophilic-hydrophobic nexus of the assembled triblock copolymer nanoaggregates by the addition of chloroauric acid (HAuCl4) followed by in situ reduction using NaBH4. After reduction, the cloudy white nanoparticle dispersions turned to a red-purple color. The gold nanoparticles that formed were stabilized by the enveloping polymeric nanostructures, neither precipitation nor agglomeration occurred. We demonstrated that we were able to tune the gold nanoparticle composition in these polymer-gold composites by varying the concentration of chloroauric acid. Morphology, particle size, molecular weight, AuNP content, and chemical structure of the polymer structures were characterized by transmittance electron microscopy (TEM), dynamic light scattering (DLS), size exclusion chromatography (SEC), thermal gravimetric analysis (TGA), and 1H NMR. Finally, the formation of the AuNPs occurred without affecting the polymer nanoparticle morphology.