Gold Bulletin最新文献

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.

Nanotechnology is an emerging field with a multitude of applications in medicine, agriculture, and engineering. To date, several methods are used for the synthesis of metallic nanoparticles including chemical, physical, and green methods. The later method is preferred for the synthesis of NPs due to its safe nature, efficiency, and minimal toxicity. Recently, gold nanoparticles (AuNPs) have been attracting attention due to their excellent biocompatibility and diverse medical applications. A diverse group of microorganisms or their metabolites (bacteria, fungi, and yeast) have been utilized to synthesize AuNPs from their respective bulk salts. This review focuses on the resources exploited for biosynthesis of AuNPs, the current understanding about their synthesis, and the emerging trends, along with their mechanistic antimicrobial and anticancer applications. This review also highlights the current challenges and future potential applications of AuNPs.

Chloroalkanes have richer structures and cheaper costs than iodide/brominated compounds, while rarely used as electrophilic reagents for constructing C(sp³)–C(sp³) bonds due to their low reduction potential and strong bond dissociation energy. Recently, a new catalytic strategy involving dinuclear gold complexes has overcome this limitation. The photoinduced gold-catalyzed mode initiated the C(sp³)–Cl electrophilic activation, lead to the divergent conversion of chloroalkanes as chloroalkyl, alkyl cation and carbene equivalent precursor of carbon chain propagation, and involved a novel mechanism of inner-sphere SET process between dinuclear gold complex catalyst and chloroalkane.

Etching solutions of spent printed circuit boards contain a small amount of valuable metals like Au(III) and Pd(II). In order to meet the increasing demand for gold and palladium, it is necessary to recover these metals from the etching solutions. In this work, solvent extraction experiments were done to separate Au(III) from the synthetic hydrochloric acid solutions containing Pd(II), Cu(II), and Ni(II). Single Cyanex 272 and TBP and their mixture were employed to investigate the selective extraction of Au(III) from other metal ions in the HCl concentration range from 1 to 9 M. Single Cyanex 272 and the mixture of Cyanex 272 and TBP successfully separated Au(III) from the solution, while a small amount of Pd(II), Cu(II) and Ni(II) were co-extracted with Au(III) by TBP. The mixture of Cyanex 272 and TBP showed synergism for the extraction of Au(III). The dependence of Au(III) extraction on the mole fraction of TBP in the mixture was pronounced when HCl concentration was 1 and 3 M. The Au(III) loaded into the mixture was completely stripped by low concentration of thiourea and sodium thiosulfate. Pure gold metal was recovered from the thiourea stripping solution by chemical reduction with ascorbic acid. Complete reduction of Au(III) was possible at 80 °C for 30 min when the molar ratio of ascorbic acid to Au(III) was 20.

Cancer was the world’s second major cause of death. Several treatments were available, including chemotherapy, radiotherapy, immunotherapy, and surgery. However, they are restricted due to their risk to normal cells, their ability to destroy the immune system, and conferring increased risk of secondary cancer development. Nanotechnology was extensively researched and used in cancer treatment because nanoparticles could play an essential role in drug delivery. Furthermore, nanoparticle drug delivery systems have been shown to help overcome cancer-related drug resistance. Gold nanoparticles have unique physical, chemical, and biological properties, making them suitable candidates for non-toxic drug carriers. Because of their nanorange size, surface modifications of gold nanoparticles could improve their stability, minimize nanoparticle aggregation, and enhance attachment to anti-cancer agents and target cells, further increasing their ability to penetrate cell membranes and reduce toxicity. This review aims to discuss the current research in targeting drug delivery for anti-cancer agents using gold nanoparticles. By conducting a literature search through the PubMed and Scopus database up to April 2022 using the term gold nanoparticles, targeted drug delivery, chemotherapy, gene therapy, and cancer, this review summarized report on the implementation of gold nanoparticles for targeted drug-delivery systems for cancer therapeutics. The targeting ligands included folic acid, aptamers, hyaluronic acid, glutathione, peptides, and antibodies. According to the findings of studies, implementing gold nanoparticles as nanocarriers significantly improves drug delivery of anti-cancer agents to cancer cells without affecting other untargeted cells. Enhanced cell uptake, increase in drug toxicity, inhibition of tumor growth, and selective drug target are also reported to be the advantages of gold nanoparticle-based targeted drug delivery carriers.