Gold Bulletin最新文献

To make the most of the unique properties of nanomaterials, and to bridge the gap between fundamental and applied research, controlled, green, cheap and energy efficient syntheses of nanoparticles are required. In this respect, room and low temperature surfactant-free colloidal syntheses of nanoparticles obtained in low viscosity and low boiling point solvents, without additives or nature-derived extracts, are promising to develop more active (electro)catalysts. Recently, a room temperature synthesis of surfactant-free gold nanoparticles has been documented (Chem. Mater. 2023, 35, 5, 2173) that requires only water, a base such as NaOH, an alcohol and HAuCl₄. Unfortunately, the syntheses of nanomaterials are often sensitive to multiple parameters and it is well acknowledged that reproducibility is a general challenge in the chemical sciences, where the synthesis of nanomaterials is no exception. Here, we investigate the effect of the water conductivity and solvent grade on the surfactant-free low temperature (ca. 30 °C) synthesis of colloidal gold nanoparticles obtained in alkaline mixtures of ethanol and water. The synthesis can be performed with relatively low-grade ethanol but requires high purity water. The importance of water with low conductivity is also stressed for syntheses where ethylene glycol and glycerol are used as source of reducing agents. The results of this study over 100 samples pave the way to greener, more controlled and scalable syntheses of surfactant-free gold nanomaterials.

To elucidate an antitumor drug exhibiting enhanced activity relative to cisplatin, a novel dinuclear gold(III) complex was synthesized, incorporating 1,5-naphthyridine as a bridging ligand. Subsequently, the newly synthesized complex underwent comprehensive characterization using various techniques to validate its structural attributes. The stability of the complex in both water and PBS buffer was assessed through UV–Vis spectroscopy. DNA binding studies were conducted employing UV–Vis, fluorescence spectroscopy, and viscosity measurements. Competitive studies with ethidium bromide (EB) or 4′-hydroxyethidium (HOE) were performed utilizing fluorescence spectroscopy. The findings indicated that the dinuclear gold(III) complex interacts with calf thymus DNA (CT-DNA) through a groove binding mode. Moreover, the investigated complex exhibited significant binding constants for its interaction with human serum albumin (HSA) and bovine serum albumin (BSA) and interactions in the presence of site markers (eosin Y or ibuprofen). The dinuclear gold(III) complex demonstrated notable cytotoxicity against HCT116 and MDA-MB-231 cancer cell lines at 24 and 72 h post-treatment. Furthermore, the complex displayed selectivity by inducing significantly lower cytotoxic activity in healthy cells than in cancerous ones. In support of its antitumor activity, the complex exhibited proapoptotic effects, as evidenced by increased caspase 9 activity and low percentages of necrosis. Molecular docking simulations were employed to corroborate all experimentally obtained results.

The Heck reaction has been considered a robust method for the cross-coupling reaction of olefins and aryl halides to yield alkenes. However, the most significant requirement is the necessity of electronically biased olefins and the requirement of directing group to control the regioselectivity of the Heck reaction. The research group of Patil and Gandon recently documented the gold-catalyzed Heck reaction, demonstrating the utilization of simple aliphatic alkenes as substrates. This approach does not need electronically biased olefins and offers a distinct regioselectivity when compared to the Heck reaction catalyzed by other transition metal catalysts.

The utilization of engineered gold nanoparticles (GNPs) in biomedical applications is experiencing rapid growth owing to their reactive nature and remarkable flexibility. However, despite these advantages, concerns persist regarding their in vivo biocompatibility and cytotoxicity. This study aimed to assess the toxicity, biodistribution, and excretion pathways of GNPs functionalized with various antibiotics, namely, ciprofloxacin, levofloxacin, cefotaxime, and ceftriaxone, using a mouse model. Following intravenous administration, the nanostructures induced an increase in serum enzyme levels and histological abnormalities in the liver, indicating potential hepatotoxic effects. Analysis of organ distribution revealed accumulation primarily in the liver and spleen, with concentrations gradually decreasing 168-h post-administration. Fecal excretion was identified as the primary route of elimination, with a smaller portion excreted via urine. Among the different nanostructures evaluated, those functionalized with levofloxacin (LEV-NP) exhibited minimal organ toxicity and a high clearance rate. Additionally, LEV-NP, with a size of approximately 12 nm, demonstrated superior drug particle stability and lower red blood cell hemolytic activity compared to other nanostructures.

A simple microextraction method has been developed for the preconcentration of Au(III) and its measurement by an ultraviolet–visible spectrophotometer. Benzalkonium chloride, a cationic surfactant, was used as a complexing agent for the preconcentration of Au(III) in the form of AuCl₄⁻. An ion pair between AuCl₄⁻ and benzalkonium chloride was finely extracted into the 1,2-dichloroethane phase through a simple emulsification process. Parameters affecting the preconcentration of Au(III) were evaluated, including the acidity of the solution, the amount of the cationic reagent, and the effect of interferences. The calibration curve of the method for Au(III) was linear in the range of 0.05–0.80 mg L⁻¹. The detection limit, enrichment factor, and relative standard deviation were 0.01 mg L⁻¹, 40, and 1.9%, respectively. The accuracy of the method was evaluated through addition-recovery tests on real water samples. The results demonstrate that this microextraction method was successfully applied to stream water samples for the preconcentration of Au(III).

The synthesis of gold nanoparticles (AuNPs) by bottom-up methods, such as redox reactions using amino acids and gold salts, has turned out to be a novel method for obtaining nanoparticles due to the reducing properties of these biomolecules and the ability to give the nanoparticle peculiar physicochemical characteristics for its biological application, thus derived from the known structure and amino acids functional groups. In this sense, this work shows the characterization using UV-Vis, DLS, FTIR, XPS, and HRTEM techniques of AuNPs synthesized using sodium borohydride (NaBH₄) as a reducing compound and L-cysteine methyl ester hydrochloride (cysteine precursor) (HSCH₂CH (NH₂) COOCH₃ • HCl) as a stabilizing agent. The above elucidates the reaction mechanisms for the formation of the nanoparticle through these reactions, as well as the stabilizing action and possible reducing potential of cysteine. Likewise, the resulting Cis@AuNP compounds were subjected to a preliminary biological evaluation using cell viability toxicity tests. The Cis@AuNPs showed high colloidal stability in a pH range of 3 to 11, where the L-cysteine methyl ester hydrochloride functional groups strongly influenced the hydrodynamic diameter and zeta potential behavior. Cytotoxicity assays in mouse leukocytes demonstrated the safety of these nanoparticles. These encouraging results open the way to explore the biological application potential of these systems with the perspective of their possible application in vaccinology.

Since their discovery, graphene nanocomposites have attracted much attention for their potential use in many biological applications. Herein, we examined the highly reduced graphene oxide (HRGO) and gold nanomaterial (AuNM)-based (HRGO/Au@AP) nanocomposite for ovarian cancer and apoptosis-inducing abilities, the nanomaterials’ anticancer activities against human ovarian cancer cell lines (SKOV3 and A2780). HRGO was functionalized with the 1-aminopyridine (AP) as a potential stabilizing agent to improve the sample’s solubility and bioavailability. The surface morphology and structure of the nanocomposites were examined by high-resolution transmission electron microscopy. The results of an anticancer study comparing HRGO, HRGO/Au, and HRGO/Au@AP nanocomposites showed a greater capacity to induce apoptosis, the apoptosis assays (AO-EB, DAPI, and Annexin V-FITC/PI staining) and reactive oxygen species (ROS) measurements on SKOV3 and A2780 cells. This data suggests that HRGO/Au@AP promotes potent apoptosis in human ovarian cancer cells.

The global pandemic of coronavirus disease 2019 (COVID-19) has come to a different stage worldwide. Until now, the common flu-like outbreaks have led to increasing demand for screening tests with high sensitivity and specificity. Among biosensors, the noble metal nano-optical sensor based on localized surface plasmon resonance (LSPR) has great potential due to its simple design, feasible manufacturing, and fast response. To develop an efficient and economic examination, this study utilizes high power impulse magnetron sputtering (HiPIMS) to prepare ultrathin gold film (UTGF) on glass substrate. The experimental results show that with an increase in the deposition time from 3 s to 144 s, the UTGF forms from an island-like morphology, a network structure, to ultimately a smooth UTGF layer on glass. When the UTGF sample is conjugated with human serum albumin (HSA) at 5 × 10⁻⁴ M as a pretest analyte, a significant peak shift of 25.6 nm was detected for the UTGF deposited at 12 s. Based on the UV-Vis measurement, the plasmonic loss peak of the UTGF sample with deposition times of 6 s, 12 s, and 24 s are 537.1 nm, 601.9 nm, and 665.8 nm, respectively, whereas the deposition time of 12 s prepared UTGF sample revealed the strongest LSPR effect. With a prolonged deposition time over the percolation time (48 s), those UTGF samples gave no LSPR response. To further detect viral antigen, recombinant severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid (N) protein, the UTGF were functionalized with mouse anti-human immunoglobulin G (IgG). The HiPIMS prepared UTGF sample feasible for SARS-CoV-2 detection is demonstrated, giving potential application on rapid and ultrasensitive biomolecules sensor.

The catalytic efficacy of monometallic (Pd NPs) vs bimetallic nanocatalyst (Au NPs and Pd NPs supported on rGO) towards the one-pot synthesis of spirooxindole derivatives has been compared under mild reaction conditions. The multicomponent reaction comprised of reaction of substituted isatins, malononitrile, and 1,3-dicarbonyl compounds to synthesise series of diverse spirooxindoles. The nano-Au–Pd@rGO catalyst showed enhanced catalytic activity in the synthesis of spirooxindoles when compared to that of the monometallic nano-Pd/rGO catalyst which may be indicative of potential synergistic effect in the bimetallic catalyst viz Au and Pd NPs facilitating the accelerated synthesis of spirooxindoles in excellent yields. This methodology has the advantages of utilisation of non-toxic solvent, higher product yields, and lower reaction times at room temperature. Also, higher yields for spirooxindoles in case of substituted carbonyl compounds were observed, an indicative of the gem-dialkyl effect responsible to favour higher yields for spirooxindoles synthesised with di-methyl substituted cyclohexan-diones with respect to the unsubstituted ones for both catalytic systems.

Additive Manufacturing (AM) allows to manufacture new designs and novel geometries interesting for jewelry and watchmaking items. However, pure gold and gold alloys are challenging materials to manufacture by Laser Powder Bed Fusion (LPBF). Due to the low absorptivity at 1 064 nm Infrared (IR) wavelength combined to high thermal conductivity, it is difficult to manufacture pure gold and gold-based alloys by this process. Recent evolutions in laser technology allowed to build a machine using a 515 nm “green” laser. By changing the wavelength (1 064 nm to 515 nm), absorptivity can be improved from 7 to 37%. This paper will focus on 18 karat gold single tracks analysis produced by both wavelengths on a steel substrate. Different melting states will be detailed and indexed in order to select, correctly, machine parameters for producing gold items. It will be shown that 515 nm laser is more adapted to the material than 1 064 nm laser for manufacturing gold alloys.