Water-dispersed Gold Nanoparticles Research Articles

Novel gluconate stabilized gold nanoparticles as a colorimetric sensor for quantitative evaluation of spermine

In the fields of biology and pharmacy, water dispersible gold nanoparticles (AuNPs) with bio-friendly capping agents are always in demand. Gluconate is a substance that is compatible with biological systems. Gluconate stabilized AuNPs (abbrv.: Glu-AuNPs) were synthesized in water and characterized utilizing UV-Vis spectroscopy, DLS, TEM, and Raman spectroscopy tools, as well as a DFT computing investigation. The Glu-AuNPs are extremely stable in the pH range of 4–10 and exhibit SPR band maximum at 518 nm. According to TEM and DLS investigation, the particle sizes are 7.03 ± 2 nm and 14 nm, respectively. They have an FCC crystalline structure. The Raman and DFT computation studies reveal that the gluconate ions adsorbed onto the surface of AuNPs and provided much needed stability of the particles against agglomeration. The computed binding energy of Glu-O(COO) to Au3 cluster is − 5.22 eV, which is quite high. The particles have been ascertained as colorimetric and UV-Vis spectrophotometric nanosensor for spermine (SM), a biomarker for cancer diagnosis. The SM was quantified by monitoring changes in the feature of the SPR band maximum of Glu-AuNPs as a result of its aggregation. The LoD value is 0.2511 μM. As evidenced by the computed Kasso value of 2.183 × 106 M−1, the SM---AuNPs interactions are quite strong. The nanosensor exhibits excellent recovery results against real samples.

Benzene-1,3-disulfonate capped gold nanoparticles: DFT computations in support of particles-capping agent and nano-sensing interactions

We have successfully synthesized water-dispersible gold (Au) nanoparticles (NPs) using benzene disulfonate anions (BDS2−) as a capping agent and applied them for the colorimetric recognition of Pb2+ and Cu2+ ions in aqueous solutions. The synthetic method for the BDS-AuNPs is very simple, one-pot and rapid. The particles are stable in a wide pH range of 5 to 10 over a month and are small in size (dTEM=8.9nm and dDLS=17nm). They selectively bind Pb2+ and Cu2+ ions over 14 other metal ions. This makes the particles an efficient optical dual-nanosensor. The limit of detection (LOD) values for Pb2+(0.469 μM) and Cu2+ (0.645 μM) ions are quite low. The association constant values for the Pb2+----BDS-AuNPs and Cu2+-----BDS-AuNPs complexes are found to be 1.612 × 106 M−1 (R2 adj. 0.9603) and 8.12 × 105 M−1 (R2 adj 0.9947), respectively, indicating strong interactions between the particles and the metal ions. A DFT computational study reveals that the binding affinity of BDS to the Aun cluster increases with the increase of Au atoms in the Aun cluster, supporting the experimental findings. The practical acceptance of the sensor was tested with real samples, where the sensor showed excellent recovery results. So, the BDS-AuNPs could be treated as an easy-to-develop dual-nanosensor for Pb2+ and Cu2+ metal ions.

Hybrid Multivalent Jack Bean α-Mannosidase Inhibitors: The First Example of Gold Nanoparticles Decorated with Deoxynojirimycin Inhitopes.

Among carbohydrate-processing enzymes, Jack bean α-mannosidase (JBα-man) is the glycosidase with the best responsiveness to the multivalent presentation of iminosugar inhitopes. We report, in this work, the preparation of water dispersible gold nanoparticles simultaneously coated with the iminosugar deoxynojirimycin (DNJ) inhitope and simple monosaccharides (β-d-gluco- or α-d-mannosides). The display of DNJ at the gold surface has been modulated (i) by using an amphiphilic linker longer than the aliphatic chain used for the monosaccharides and (ii) by presenting the inhitope, not only in monomeric form, but also in a trimeric fashion through combination of a dendron approach with glyconanotechnology. The latter strategy resulted in a strong enhancement of the inhibitory activity towards JBα-man, with a Ki in the nanomolar range (Ki = 84 nM), i.e., more than three orders of magnitude higher than the monovalent reference compound.

Hard core proof of the polyvinyl alcohol as a reducer for the formation of gold nanoparticles

In this paper, we report the direct synthesis of water dispersed gold nanoparticles encapsulated in polyvinyl alcohol (PVA), which acting as reducer to gold ion to gold metal and capping agent. The syntheses of the gold nanoparticles were carried with the direct addition of the aqueous HAuCl4 solution to aqueous PVA solution at 50 °C. Initially, the PVA solution was prepared by using 2 g of PVA per 100 ml of distilled water in a round bottom flask which was placed in oil bath placed over the magnetic stirrer. Subsequently, the aqueous solution HAuCl4 was added drop-wise to the PVA solution. Afterward, the solution was made viscous by heating at same temperature and casted in form of nanocomposites films. Various compositions of HAuCl4 (0.2 wt%, 0.5 wt%, 1.0 wt% and 1.5 wt%) with respect to PVA (films of Au-PVA nanocomposites) were prepared. Upon drying in ambient condition these films were analyzed with XRD, SEM, EDX, TGA, UV–Visible, and IR techniques. The XRD analysis reveals the fcc crystal structure with crystallite size nearly 22 nm. The crystallite size is in agreement with that obtained by SEM analysis which is in range of 25–30 nm and particles are nearly spherical in shape. Furthermore, the UV–visible analysis showed the surface plasmon resonance (SPR) band at ~ 550 nm which confirmed the formation of gold nanoparticles. It is further supported by the EDX analysis that showed the gold peaks in the spectrum.

A catalytic study of water dispersed gold nanoparticles for the hydrolytic oxidation of diorganosilanes - en route formation of a Pickering catalyst and synthesis of tetraorganodisiloxane-1,3-diols.

Water-dispersed gold nanoparticles decorated with an amphiphilic cyclotetrasiloxane scaffold hold promise for the catalytic transformation of diorganosilanes to tetraorganodisiloxane-1,3-diols, (RR1SiOH)2O [R = Me or Ph R1 = Ph, cyclo-Hex] via en route formation of a Pickering emulsion. The recognition ability of these compounds toward Cl- ions reveals 2 : 1 receptor-anion complexation.

Facile construction of calix[4]pyrrole-templated gold nanoparticles: computational insights and application for efficient reduction of 4-nitrophenol

Herein, we report a simple one-pot synthesis of water-dispersible gold nanoparticles (AuNPs) by using meso-tetra(methyl) meso-tetra hydrazide-functionalized calix[4]pyrrole (ECPTH) as both reducing and stabilizing template. The characterization of ECPTH-AuNPs has been carried out by UV-Vis spectroscopy, transmission electron microscope, X-ray diffraction (XRD), dynamic light scattering (DLS), and zeta potential techniques. The spherical shaped nanoparticles are highly stable with an average size of 8 ± 2 nm. The mechanistic insights rendered by the computational study have suggested that ECPTH can successfully cap the Au via utilizing the hydrazide arms. The nanoparticles functioned as an effective heterogeneous catalyst for the 4-nitrophenol reduction and ECPTH as capping ligand enhances the catalytic activity via a synergistic effect. This work contributes a new catalytic pathway for the degradation of hazardous and toxic pollutants using highly efficient and cost-effective supramolecular-functionalized nanocatalyst.

Water dispersed gold nanoparticles catalyzed aerobic oxidative cross-dehydrogenative coupling: An efficient synthesis of α-ketoamides in water

An effective green synthesis of α-ketoamides was developed for the first time in water via gold nanoparticles (AuNPs) catalyzed aerobic oxidative cross-dehydrogenative coupling of secondary amines with phenylglyoxals with a broad substrate scope.

Enhancement of photon absorption in the light-harvesting complex of isolated chloroplast in the presence of plasmonic gold nanosol—a nanobionic approach towards photosynthesis and plant primary growth augmentation

A strong enhancement of electromagnetic field generated through resonating surface polaritons on metal films and particles has stimulated considerable interest in diverse research fields such as photobiology as, for example, in photosynthesis. This surface plasmon resonance (SPR) of metal nanoparticles (NPs) can augment photosynthetic chemical energy production in an artificial photosynthetic model system. In this paper, the effect of three water-dispersible gold NPs (GNPs) of nearly similar size but with different surface moieties (aspartate, bovine serum albumin, and citrate capping) is experimentally shown on the photosynthetic efficiency of isolated chloroplasts of Vigna radiata. It was found that GNPs can augment photon absorption in the light-harvesting molecular complexes (LHMCs) and can cause increased distinctive optical and electronic properties. Photosynthetic light reactions like electron transport rate, photophosphorylation, and oxygen evolution rate were increased in the presence of GNPs, indicating higher photosynthetic activity. The rate of increase was dependent on the surface capping of GNPs, and it was maximum in case of citrate-capped GNP. Moreover, it was also found that these GNP-induced enhancements had positive correlation with the primary growth parameters of V. radiata.

Thiacalix[4]arene functionalized gold nano-assembly for recognition of isoleucine in aqueous solution and its antioxidant study

Thiacalix[4]arenes comes under heteracalixarene class which has notable utility in the area of nanoscience. This stimulation has led to the synthesis of water-dispersible gold nanoparticles (AuNps) using thiacalix[4]arene tetrahydrazide (TCTH) as both reducing as well as stabilizing agent. The synthesized nanoparticles (TCTH-AuNps) were characterized by SPR, TEM and EDX. TCTH-AuNps were found to be selective and sensitive for isoleucine. The concentration of isoleucine was detected in the limit of 1nM to 1.2μM based on fluorescence enhancement. TCTH-AuNps were also used to measure antioxidant capacityagainst the standard ascorbic acid.

Detection of Gold Nanoparticles in Rat Organs by Transmission Electron Microscopy.

The effects of water-dispersed gold nanoparticles (8.0±0.9 nm in diameter) on the rat small intestinal mucosa and Peyer plaques, liver, and spleen were studied by electron microscopy. Water-dispersed gold nanoparticles injected into isolated intestinal loop not only accumulated in the small intestinal mucosa and Peyer plaques, but also penetrated into other organs, e.g. liver and spleen. Ultrastructural changes in the cells (hyperplasia of endoplasmic reticulum) were detected in the studied organs.

Colour tuneable anisotropic, water-dispersible gold nanoparticles stabilized by chitosan

We present a novel one-pot synthesis of stable water dispersible multi-branched anisotropic gold nanoparticles using hydrazine as the principal reducing agent and chitosan as the secondary reducing agent, growth directing agent and stabilizer. They are colour tuneable in the purple to blue range due to the presence of both transverse and longitudinal overlapping localized surface plasmon resonance (LSPR) absorptions arising from the multi-branched nanoparticle morphology. The longitudinal LSPR absorbance tails into the near IR range. This provides a simple alternative approach to producing anisotropic gold nanoparticles.

Gold Nanoparticles as Carriers for Synthetic Glycoconjugate Vaccines.

Recent advances in the preparation and characterization of metal core-based nanoparticles have opened the way to their exploration as carriers for carbohydrate-based vaccines. Here we describe the protocols for the preparation and characterization of water dispersible gold nanoparticles (1-3 nm gold diameter) as carriers for carbohydrate antigens. We mainly refer to the protocols we used for the preparation of gold glyconanoparticles as carrier for an S. pneumoniae carbohydrate-antigen. The high number of ligands at the gold nanoparticles surface and the easiness of their one-pot preparation make these biocompatible nanomaterials an attractive tool for glyco-scientists.

Dicoumarol assisted synthesis of water dispersible gold nanoparticles for colorimetric sensing of cysteine and lysozyme in biofluids

A schematic representation of the mechanism for the colorimetric sensing of Cys and Lys using DIC–Au NPs as a probe.

Functional, water-dispersible gold nanoparticles produced with N,N′-bis(acryloyl)-(l)-cystine

Functional CiBA–AuNPs, with optical properties identical to those of TSC–AuNPs, for crosslinking reactions have no need for ligand exchange steps.

One pot, rapid and efficient synthesis of water dispersible gold nanoparticles using alpha-amino acids

A detailed study on the synthesis of spherical and monodispersed gold nanoparticles (AuNPs) using all of the 20 naturally occurring α-amino acids has been reported. The synthesized nanoparticles have been further characterized using various techniques such as absorbance spectroscopy, transmission electron microscopy, dynamic light scattering and nuclear magnetic resonance. Size control of the nanoparticles has been achieved by varying the ratio of the gold ion to the amino acid. These monodispersed water soluble AuNPs synthesized using non-toxic, naturally occurring α-amino acids as reducing and capping/stabilizing agents serve as a remarkable example of green chemistry.

Interactions of gold nanoparticles with a phospholipid monolayer membrane on mercury.

It is demonstrated that a compact monolayer of 1,2-dioleoyl-sn-glycero-3-phosphocholine adsorbed to a hanging mercury drop electrode can serve as a simple electrochemical model system to study biomembrane penetration by gold nanoparticles. The hydrogen redox-chemistry characteristic of ligand-stabilized gold nanoparticles in molecularly close contact with a mercury electrode is used as an indicator of membrane penetration. Results for water-dispersible gold nanoparticles of two different sizes are reported, and comparisons are made with the cellular uptake of the same preparations of nanoparticles by a common human fibroblast cell line. The experimental system described here can be used to study physicochemical aspects of membrane penetration in the absence of complex biological mechanisms, and it could also be a starting point for the development of a test bed for the toxicity of nanomaterials.

Highly stable water dispersible calix[4]pyrrole octa-hydrazide protected gold nanoparticles as colorimetric and fluorometric chemosensors for selective signaling of Co(II) ions

Water dispersible stable gold nanoparticles (AuNps) have been synthesized by using calix[4]pyrrole octa-hydrazide (CPOH) as a reducing as well as stabilizing agent. CPOH-AuNps have been characterized by surface plasmon resonance, particle size analyzer and transmission electron microscopy. CPOH-AuNps are water dispersible, highly stable for more than 150days at neutral pH with a size of less than 10nm and zeta potential of 15±2MeV. Ion sensing property of CPOH-AuNps has been investigated for various metal ions Pb(II), Cd(II), Mn(II), Fe(III), Ni(II), Zn(II), Hg(II), Co(II) and Cu(II) by colorimetry and spectrofluorimetry. Among all the metal ions investigated, only Co(II) ions gives sharp colour change from ruby red to blue and is easily detectable by naked-eye. CPOH-AuNps being fluorescent in nature also shows great sensitivity and selectivity for Co(II) ions. Co(II) ions can be selectively detected at very low concentration level of 1nM in a facile way of fluorescence quenching.

Responses of RAW264.7 macrophages to water‐dispersible gold and silver nanoparticles stabilized by metal–carbon σ‐bonds

Nanometals are currently receiving considerable attention for industrial and biomedical applications, but their potentially hazardous and toxic effects have not been extensively studied. This study evaluated the biological responses of novel water-dispersible gold (Au-NPs) and silver nanoparticles (Ag-NPs) stabilized by Au-C or Ag-C σ-bonds in cultured macrophages (RAW264.7), via analysis of the cell viability, the integrity of the plasma membrane, and the inflammatory and morphological properties. The cultured RAW264.7 was exposed to metal-NPs at various concentrations. The Ag-NPs showed cytotoxicity at high NP concentrations, but the cytotoxic effects of the Au-NPs were smaller than those of the Ag-NPs. For the microscopic analysis, both types of particles were internalized into cells, the morphological changes in the cells which manifested as an expansion of the vesicles' volume, were smaller for the Au-NPs compared with the Ag-NPs. For the Ag-NPs, the endocytosis abilities of the macrophages might have induced harmful effects, because of the expansion of the cell vesicles. Although an inflammatory response was observed for both the Au- and Ag-NPs, the harmful effects of the Au-NPs were smaller than those of the Ag-NPs, with minor morphological changes observed even after internalization of the NPs into the cells.

Double Hydrophilic Block Copolymer Templated Au Nanoparticles with Enhanced Catalytic Activity toward Nitroarene Reduction

We present a facile method for synthesizing water-dispersible gold nanoparticles (Au NPs) using a double hydrophilic block copolymer (DHBC), poly(ethylene oxide)-block-poly(acrylic acid) (PEO-b-PAA), as a template and demonstrate their application in the reduction of nitroarenes. Selective coordinative interactions between a gold precursor and the PAA block of the DHBC lead to the formation of micelles, which are subsequently transformed into Au NPs with an average diameter of 10 nm using a reducing agent. The DHBC-templated Au NPs (Au@DHBC NPs) remain stable in water for several months without any noticeable aggregation. Furthermore, Au@DHBC NPs are found to be highly effective in catalyzing the reduction of a series of nitroarenes. Remarkably, the turnover frequency in the case of 4-nitrophenol using Au@DHBP NPs reaches 800 h–1, outperforming previously reported Au NP-based catalytic systems. We believe the enhanced catalytic activity is due to the DHBC shell around Au NPs, which templates the formation...

Adsorption Behaviour of PEGylated Gold Nanoparticles to Different Surfaces Probed by CV Monitoring

Non-adsorption of water dispersible gold nanoparticles (GNPs) is a major concern in its widely labeling applications. This paper presents the investigation of the adsorption properties of GNPs with superficially tethered ferrocene functions to different surfaces. The GNPs were coated with a mixed monolayer of PEG-thiol and progargyl PEG-thiol, and the later was linked with a ferrocene moiety (Fc) through the alkyne-azide click reaction. The adsorption behaviors of the Fc-GNP to glassy carbon, gold and platinum electrodes, in the absence and presence of a self-assembled monolayer (SAM) or protein layer, were studied by cyclic voltammetry (CV). It was found that the bare gold electrode possessed higher adsorption capacity. However, the adsorption was either reduced or completely prevented when the gold electrode was modified with monolayers of 2-mercaptoethanol (ME), dodecanethiolate (DT) and PEG-thiol. The electroactive and water dispersible GNPs with Fc labels allows us to use CV to explore the interaction between these GNP and bovine serum albumin (BSA). The BSA modified electrode resulted in better resistant to adsorption compared to other modifiers coated electrodes. Thus, the study of non-specific interaction by CV was found effective when compared to results obtained by surface plasmon resonance (SPR) and FTIR.