Gold Salts Research Articles

Voltammetric determination of nitrite with gold nanoparticles/poly(methylene blue)-modified pencil graphite electrode: application in food and water samples

This work presents the preparation and characterization studies of gold nanoparticle/poly(methylene blue) (GNP/PMB)-modified pencil graphite electrode (PGE) and its use for electrochemical determination of nitrite. The working electrode (PGE) was functionalized by electropolymerization of methylene blue (MB) and modified with gold nanoparticles (GNPs) to produce the final (GNP/PMB/PGE) electrode in a two-step procedure. Characterization and morphology studies of GNP/PMB/PGE were performed by electrochemical impedance spectroscopy, cyclic voltammetry, X-ray photoelectron spectroscopy, Fourier transform Infrared spectroscopy, and scanning electron microscopy techniques. The highest peak current response was obtained for nitrite at pH 5.0. A wide linear relationship between the concentration and the oxidation peak currents of nitrite was observed in the concentration range of 5–5000 μM. The limit of detection (0.314 μM, S/N = 3) and reproducibility (RSD = 2.38% for N = 10) have been identified. Finally, the electrode platform was successfully applied to commercial sausage and mineral water samples.

A chiral responsive carbon dots-gold nanoparticle complex mediated by hydrogen peroxide independent of surface modification with chiral ligands.

Chiral recognition of enantiomers is fundamentally important. In this study, a novel strategy for the chiral discrimination of glucose enantiomers was constructed based on the hydrogen peroxide (H2O2)-mediated generation of a carbon dots-gold nanoparticle (C-dots@Au NP) complex independent of surface modification with chiral ligands. H2O2 is essential as a reductant to promote the growth of Au NPs from gold salts. Besides, the modification of C-dots with sulfhydryl groups is necessary for its anchoring on the surface of Au NPs. Therefore, in the presence of H2O2, the C-dots@Au NP complex can be self-generated from a simple mixture containing C-dots and Au salts. It is worth noting that glucose oxidase can selectively catalyze d-glucose but not l-glucose to generate H2O2. In this regard, the chiral recognition process can trigger the formation of the C-dots@Au NP complex. Furthermore, based on the production of reddish Au NPs and the reduction of C-dot fluorescence quenched by Au NPs, the resultant C-dots@Au NP complex enables achieving the chiral discrimination of glucose enantiomers by combining colorimetric and fluorometric assays. Compared with the conventional approaches that use chiral ligands to decorate NPs, the generation of the chiral-responsive C-dots@Au NP complex is much simpler and faster. Upon combination with specific enzymatic reactions that produce a reductive product, the current strategy provides a general approach for the identification of chiral enantiomers.

Gold(iii) π complexes.

π Hydrocarbons are widespread ligands and substrates in transition metal chemistry. Although gold(iii) has been known for some time to efficiently activate alkenes and alkynes towards nucleophilic addition, and to readily promote the C-H auration of arenes, the corresponding π-complexes have remained elusive until recently. This frontier article highlights recent achievements in the preparation and characterization of gold(iii) π complexes. The coordination of alkenes, alkynes and arenes to gold(iii) is presented and discussed.

A two-step synthesis for preparing metal microcapsules with a biodegradable polymer substrate.

Metal microcapsules have recently received attention and are being developed as improved carrier materials when compared to polymer microcapsules. In this work we have developed a novel, simplified method by which polymeric microcapsules can be synthesised using a combination of poly(vinyl pyrrolidone)-stabilised platinum nanoparticles (PVP-Pt) and poly(vinyl pyrrolidone) (PVP) as stabilisers, to allow for a secondary metal shell to be grown. We investigate the relationship between the molar ratio of reducing agent to platinum salt and the size of the resulting NPs and seek to develop further fundamental understanding of the factors governing the secondary metal shell thickness and quality, to allow production of cost-effective metal microcapsules without sacrificing core retention efficiency. We found that the size of the nanoparticles had no significant effect on secondary shell thickness, but did affect the quality of the resulting gold shells. Gold salt concentration was found to be a limiting factor in the electroless deposition of the metal shell. In this work, we have successfully produced PLGA microcapsules with more cost-effective gold shells, as thin as 56 ± 13 nm and capable of complete core retention of volatile actives.

Very Green Photosynthesis of Gold Nanoparticles by a Living Aquatic Plant: Photoreduction of AuIII by the Seaweed Ulva armoricana.

Light-assisted in vivo synthesis of gold nanoparticles (NPs) from aqueous solutions of dilute AuIII salts by a living green marine seaweed (Ulva armoricana) is reported for the first time. NPs synthesised using typical procedures have many associated environmental hazards. The reported methods involve green, nontoxic, eco-friendly synthetic procedures. The formation of AuNPs was extremely rapid (≈15 min) following illumination of the living U. armoricana, while the rate of NP formation in the dark was very slow (over 2 weeks). The properties of the AuNPs formed were confirmed using a battery of spectroscopic techniques. U. armoricana were found to be very efficient in Au0 uptake, and this, together with the rapid formation of AuNPs under illumination, indicated that the seaweed remained living during NP formation. The TEM images supported this, revealing that the thylakoid membranes and cell structure remained intact. The AuNPs formed on the surface of U. armoricana thallus, along the cell walls and in the chloroplasts. Without further workup, the dried, U. armoricana-supported AuNPs were efficient in the catalytic reduction of 4-nitrophenol, demonstrating the completely green cycle of AuNP formation and catalytic activity. The results mean that an aquatic plant growing in water rich in gold salts could bio-accumulate AuNPs from its aquatic environment, simply with the activation of sunlight.

Highly sensitive naked eye detection of Iron (III) and H2O2 using poly-(tannic acid) (PTA) coated Au nanocomposite

In the present study, we present a room temperature-, one-pot method for the synthesis of functional poly (tannic acid) (PTA)-based core@shell nanocomposites (core@PTA). The addition of tannic acid (TA) to gold (Au) salt solutions at mildly alkaline pH induced reduction of the metal salts to Au nanoparticles (NPs) while TA was oxidized and self-polymerized before encapsulating the AuNPs to form Au@PTA. Through the use of coordination chemistry, the synthesized Au@PTA was utilized as a naked eye sensor for iron (III) ions and H2O2. In the presence of Fe3+, Au@PTA aggregated and resulted in visible color change, showing high selectivity towards Fe3+ with visual detection limit of 20 μM. Extension of the approach is used to detect H2O2 with visual detection limit of 0.4 μM. Observation of the UV–vis spectra after the addition of analytes for the two detection systems revealed an additional peak in the H2O2 detection system at ∼ 650 nm. This is due to the presence of “wire-like” oligomer structures in the H2O2 detection system as opposed to nanocomposite aggregation observed in the former system.

Additive manufacture of complex 3D Au-containing nanocomposites by simultaneous two-photon polymerisation and photoreduction

The fabrication of complex three-dimensional gold-containing nanocomposite structures by simultaneous two-photon polymerisation and photoreduction is demonstrated. Increased salt delivers reduced feature sizes down to line widths as small as 78 nm, a level of structural intricacy that represents a significant advance in fabrication complexity. The development of a general methodology to efficiently mix pentaerythritol triacrylate (PETA) with gold chloride hydrate (HAuCl4∙3H2O) is reported, where the gold salt concentration is adjustable on demand from zero to 20 wt%. For the first-time 7-Diethylamino-3-thenoylcoumarin (DETC) is used as the photoinitiator. Only 0.5 wt% of DETC was required to promote both polymerisation and photoreduction of up to 20 wt% of gold salt. This efficiency is the highest reported for Au-containing composite fabrication by two-photon lithography. Transmission Electron Microscopy (TEM) analysis confirmed the presence of small metallic nanoparticles (5.4 ± 1.4 nm for long axis / 3.7 ± 0.9 nm for short axis) embedded within the polymer matrix, whilst X-ray Photoelectron Spectroscopy (XPS) confirmed that they exist in the zero valent oxidation state. UV-vis spectroscopy defined that they exhibit the property of localised surface plasmon resonance (LSPR). The capability demonstrated in this study opens up new avenues for a range of applications, including plasmonics, metamaterials, flexible electronics and biosensors.

Inhibition of Bacteria Associated with Wound Infection by Biocompatible Green Synthesized Gold Nanoparticles from South African Plant Extracts.

Unlike conventional physical and chemical methods, the biogenic synthesis of gold nanoparticles (GNPs) is considered a green and non-toxic approach to produce biocompatible GNPs that can be utilized in various biomedical applications. This can be achieved by using plant-derived phytochemicals to reduce gold salt into GNPs. Several green synthesized GNPs have been shown to have antibacterial effects, which can be applied in wound dressings to prevent wound infections. Therefore, the aim of this study is to synthesize biogenic GNPs from the South African Galenia africana and Hypoxis hemerocallidea plants extracts and evaluate their antibacterial activity, using the Alamar blue assay, against bacterial strains that are known to cause wound infections. Additionally, we investigated the toxicity of the biogenic GNPs to non-cancerous human fibroblast cells (KMST-6) using 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay. In this paper, spherical GNPs, with particle sizes ranging from 9 to 27 nm, were synthesized and fully characterized. The GNPs from H. hemerocallidea exhibited antibacterial activity against all the tested bacterial strains, whereas GNPs produced from G. africana only exhibited antibacterial activity against Pseudomonas aeruginosa. The GNPs did not show any significant toxicity towards KMST-6 cells, which may suggest that these nanoparticles can be safely applied in wound dressings.

Highly sensitive and simple liquid chromatography assay with ion-pairing extraction and visible detection for quantification of gold from nanoparticles

A simple isocratic HPLC method using visible detection was developed and validated for the quantification of gold in nanoparticles (AuNP). After a first step of oxidation of nanoparticles, an ion-pair between tetrachloroaurate anion and the cationic dye Rhodamine B was formed and extracted from the aqueous media with the help of an organic solvent. The corresponding Rhodamine B was finally quantified by reversed phase liquid chromatography using a Nucleosil C18 (150mm × 4.6mm, 3µm) column and with a mobile phase containing acetonitrile and 0.1% trifluoroacetic acid aqueous solution (25/75, V/V) at 1.0mLmin−1.and at a wavelength of 555nm. The method was validated using methodology described by the International Conference on Harmonization and was shown to be specific, precise (RSD < 11%), accurate and linear in the range of 0.1 – 30.0µM with a lower limit of quantification (LLOQ) of 0.1µM. This method was in a first time applied to AuNP quality control after their synthesis. In a second time, the absence of gold leakage (either as AuNP or gold salt form) from nanostructured multilayered polyelectrolyte films under shear stress was assessed.

Assessment of metal sensitizer potency with the reconstructed human epidermis IL-18 assay

According to the new EU Medical Devices (MDR) legislation coming into effect in 2017, manufactures will have to comply with higher standards of quality and safety for medical devices in order to meet common safety concerns regarding such products. Metal alloys are extensively used in dentistry and medicine (e.g. orthopedic surgery and cardiology) even though clinical experience suggests that many metals are sensitizers.The aim of this study was to further test the applicability domain of the in vitro reconstructed human epidermis (RhE) IL-18 assay developed to identify contact allergens and in doing so: i) determine whether different metal salts, representing leachables from metal alloys used in medical devices, could be correctly labelled and classified; and ii) assess the ability of different salts for the same metal to penetrate the skin stratum corneum. Twenty eight chemicals including 15 metal salts were topically exposed to RhE. Nickel, chrome, gold, palladium were each tested in two different salt forms, and titanium in 4 different salt forms. Metal salts were labelled (YES/NO) as sensitizer if a threshold of more than 5 fold IL18 release was reached. The in vitro estimation of expected sensitization induction level (potency) was assessed by interpolating in vitro EC50 and IL-18 SI2 with LLNA EC3 and human NOEL values from standard reference curves generated using DNCB (extreme) and benzocaine (weak). Metal salts, in contrast to other chemical sensitizers and with the exception of potassium dichromate (VI) and cobalt (II) chloride, were not identified as contact allergens since they only induced a small or no increase in IL-18 production. This finding was not related to a lack of stratum corneum skin penetration since EC50 values (decrease in metabolic activity; MTT assay) were obtained after topical RhE exposure to 8 of the 15 metal salts. For nickel, gold and palladium salts, differences in EC50 values between two salts for the same metal could not be attributed to differences in molarity or valency. For chrome salts the difference in EC50 values may be explained by different valencies (VI vs. III), but not by molarity. In general, metal salts were classified as weaker sensitizers than was indicated from in vivo LLNA EC3 and NOEL data. Our in vitro results show that metals are problematic chemicals to test, in line with the limited number of standardized human and animal studies, which are not currently considered adequate to predict systemic hypersensitivity or autoimmunity, and despite clinical experience, which clearly shows that many metals are indeed a risk to human health.

Factors associated with use of disease modifying agents for rheumatoid arthritis in the National Hospital and Ambulatory Medical Care Survey.

We examined the treatment patterns among adults with rheumatoid arthritis (RA) and identified factors influencing access to traditional and biological disease modifying antirheumatic drugs (DMARDs). We analyzed visits recorded in the National Ambulatory Medical Care Survey from 2005 to 2014 with a RA diagnosis. The primary outcome was DMARD use (traditional and/or biological). We included prescriptions of all RA-related treatments such as traditional and biological DMARDs, glucocorticoids, gold preparations, immunosuppressants, and non-steroidal anti-inflammatory drugs. Covariates in the logistic regression models included age, gender, race/ethnicity, type of health care coverage, provider type, geographic region, and number of comorbidities. Among 1405 visits with a RA diagnosis, 60.4% (n = 807) were prescribed DMARDs and 23.8% (n = 334) biological DMARDs. In fully adjusted models, females have 1.57 times higher odds of any DMARD use (95% confidence interval (CI): 1.02-2.46). Also, Medicare beneficiaries as compared to privately insured have 2.31 times higher odds of receiving any DMARDs (95% CI: 1.40-3.82), while visits with specialist vs. general physician are 2.38 times more associated with any DMARD use (95% CI: 1.37-4.14). For biological DMARDs, Medicare beneficiaries were at 2.58 times higher odds (95% CI: 1.42-4.70) than privately insured, while visits with specialist are at 3.37 times higher odds than general physician (95% CI: 1.40-8.23). Visits with a specialist and Medicare beneficiaries were significantly associated with any DMARD or biological DMARD use. Additionally, contrary to prior evidence, race/ethnicity was not associated with any DMARD or biological DMARD use, which may indicate reduction in disparity of treatment access.

Reactivity of [{(N3N)W P] towards Gold(I) salts – Synthesis of [{(N3N)W P AuCl] and [{(N3N)W P}2Au][pftb] (pftb = Al(OC(CF3)3)4)

The reactivity of the terminal phosphido complex [(N3N)WP] (1) (N3N = tren = N(CH2CH2NSiMe3)3) towards the coinage metal salts [Au(tht)Cl] (tht = tetrahydrothiophene) as well as [Au(MeCN)4]+[pftb]− containing the weakly coordinating anion [Al(OC{CF3)3}4]−(pftb) was investigated. The complexes [{(N3N)WPAuCl] (2) as well as [{(N3N)WP}2Au]+[pftb]− (3) were formed in good yields and were characterized by spectroscopic methods, mass spectrometry and single crystal X-ray diffraction. In the solid state, all complexes present a linear coordination around the gold center but the W-P-Au-P-W unit in 3 is bent. DFT calculations shed light on the electronic structure of these complexes and show that the bending of the W-P-Au-P-W unit is due to the dispersion effects between the Me3Si groups of the tren ligand. The triple bond nature of the W-P bond is preserved in 2 and 3.

Biological synthesis of gold nanoparticles by the diatom Stephanopyxis turris and in vivo SERS analyses

Cultivation of the sea water diatom Stephanopyxis turris (S. turris) in a gold salt containing medium leads to the formation of gold nanoparticles. These biosynthesized nanoparticles were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). According to their diameter, they are classified into two groups with average diameters of around 30 and 10nm. It is demonstrated that both types of nanoparticles consist exclusively of gold. The location of the gold nanoparticles with respect to the diatom cell was revealed using surface enhanced Raman scattering (SERS). To ensure a reliable observation of SERS spectra in each measured cell, the concentration of the gold solution as well as the incubation time of S. turris in this solution were optimized. 3D Raman imaging of entire S. turris cells was performed to localize SERS spectra of compounds resulting from closely neighbored nanoparticles. Interestingly, intracellular SERS spectra were observed indicating the presence of gold nanoparticles inside S. turris cells. Further investigation shows that the SERS spectra generated by biosynthesized nanoparticles differ significantly from the conventional Raman spectrum of diatoms. While pigments are dominating the resonance enhanced Raman spectrum, SERS spectra exhibit a completely different appearance. Their bands coincide with bands in SERS spectra of various biologically relevant compounds, e.g., hydroxyurea and retinol. The biosynthesized gold nanoparticles therefore have a high potential for prospective in vivo research of algal metabolism and its regulation.

One pot synthesis of gold nanoparticles using chitosan with varying degree of deacetylation and molecular weight

Gold nanoparticles (AuNPs) were synthesized in one-step by reducing gold salt using nontoxic and biodegradable chitosan as dual roles of reducing agent and stabilizer. The obtained AuNPs were characterized with UV–vis spectroscopy and transmission electron microscopy. The results indicated that control over the size and shape of AuNPs is achieved through the careful selection of experimental conditions, such as reaction temperature, reaction time, concentration of gold salt and chitosan, and chitosan molecular parameters, i.e., degree of deacetylation (DD) and molecular weight (MW). At low chitosan concentration (0.005% and 0.01% (w/v)), individual spherical AuNPs with average particle size around 10nm were obtained regardless of chitosan DD and MW, while anisotropic AuNPs were obtained at concentration above 0.05% (w/v) for all investigated chitosan at the optimum condition (1mL of 1mmol/L HAuCl4 added to 3mL of chitosan solution reacted for 120min at 70°C). The growth of larger polygonal AuNPs was promoted as the higher concentration and lower DD chitosan was used as reducing agent and stabilizer. Au nanoplate was synthesized by water-soluble chitosan (Mv 566kDa, DD 53%) at concentration above 0.15% (w/v). Chitooligomers (Mv 2.4kDa, DD 94%) showed the highest reduction ability for Au3+ and the synthesized AuNPs exhibited aggregation on morphology. It was considered that chitosan DD and concentration played a more important role than MW in the size and shape of AuNPs.

Gold nanoparticles approach to detect chondroitin sulphate and hyaluronic acid urothelial coating

This study investigated the location of hyaluronic acid (HA)- and chondroitin sulphate (CS)-coated gold nanoparticles in rabbit bladder and evaluated gene expression of CD44, RHAMM and ICAM-1 receptors involved in HA and CS transport into the cell. Gold nanoparticles were synthesised by reduction of gold salts with HA or CS to form HA-AuNPs and CS-AuNPs. Bladder samples were incubated with CS-AuNPs and HA-AuNPs or without glycosaminoglycans. Transmission electron microscopy, optic microscopy and scanning electron microscopy were used to determine the location of the synthesised AuNPs. Real-time PCR was used to analyse expression of urothelial cell receptors CD44, RHAMM, ICAM-1, after ex vivo administration of CS-AuNPs and HA-AuNPs. We showed that HA-AuNPs and CS-AuNPs were located in the cytoplasm and tight junctions of urothelial umbrella cells; this appearance was absent in untreated bladders. There were no significant differences in gene expression levels for CD44, RHAMM and ICAM-1 receptors in treated versus control bladder tissues. In conclusion, we clearly showed the presence of exogenous GAGs in the bladder surface and the tight junctions between umbrella cells, which is important in the regeneration pathway of the urothelium. The GAGs-AuNPs offer a promising approach to understanding the biophysical properties and imaging of urothelial tissue.

Asymmetric dumbbell-shaped silver nanoparticles and spherical gold nanoparticles green-synthesized by mangosteen (Garcinia mangostana) pericarp waste extracts.

Mangosteen (Garcinia mangostana) pericarp waste extract was used to synthesize gold and silver nanoparticles by a green strategy. The extract was both a reducing and stabilizing agent during synthesis. Phytochemical screening of the extract was conducted to obtain information regarding the presence/absence of primary and secondary metabolites in the extract. The in vitro antioxidant activity results demonstrated that the extract had excellent antioxidant activity, which was comparable to a standard (butylated hydroxy toluene). Spherical gold nanoparticles (gold nanoparticles green synthesized by mangosteen pericarp extract [GM-AuNPs]) with an average size of 15.37±3.99 to 44.20±16.99 nm were observed in high-resolution transmission electron microscopy (HR-TEM) images. Most interestingly, the silver nanoparticles (silver nanoparticles green synthesized by mangosteen pericarp extract [GM-AgNPs]) had asymmetric nanodumbbell shapes where one tail grew from a spherical head. The average head size was measured to be 13.65±5.07 to 31.08±3.99 nm from HR-TEM images. The hydrodynamic size of both nanoparticles tended to increase with increasing extract concentration. Large negative zeta potentials (−18.92 to −34.77 mV) suggested that each nanoparticle solution possessed excellent colloidal stability. The reaction yields were 99.7% for GM-AuNPs and 82.8% for GM-AgNPs, which were assessed by inductively coupled plasma optical emission spectroscopy. A high-resolution X-ray diffraction pattern confirmed the face-centered cubic structure of both nanoparticles. Based on phytochemical screening and Fourier transform infrared spectra, the hydroxyl functional groups of carbohydrates, flavonoids, glycosides, and phenolic compounds were most likely involved in a reduction reaction of gold or silver salts to their corresponding nanoparticles. The in vitro cytotoxicity (based on a water-soluble tetrazolium assay) demonstrated that GM-AgNPs were toxic to both A549 (a human lung cancer cell) and NIH3T3 (a mouse fibroblast cell). The cytotoxicity of GM-AgNPs on A549 cells was related to apoptotic cell death. However, GM-AuNPs did not show any significant cytotoxicity to either cell. These results suggest that GM-AuNPs have the potential to be drug delivery vehicles or carriers for pharmaceutical and biomedical applications.

Facile reduction and stabilization of ginsenoside-functionalized gold nanoparticles: optimization, characterization, and in vitro cytotoxicity studies

Gold nanoparticles (GNPs) are forecasted to provide an attractive platform in biomedicine and catalysis with their potentials of combining a variety of biophysicochemical properties into an integrated nanodevice with great therapeutic and optical functions. There are several reports of crude plant extracts mediating the conversion of metal ions into nanoparticles. However, we aimed to investigate the capability of single bioactive compounds, namely ginsenosides compound K (C-K) and Rh2, to accommodate a synergistic chemical reduction of gold salts by one-pot green chemistry. Ginsenosides C-K and Rh2 are unique triterpenoid saponins present in Panax ginseng Meyer, a perennial plant traditionally used as an oriental medicinal herbal with long history. C-K and Rh2 have demonstrated diverse pharmacological properties such as anticancer, anti-inflammation, anti-aging, and neuroprotective properties. The reduction of gold ions by these ginsenosides led to the production of nontoxic GNPs as tested in mouse macrophage (J774A.1) and human kidney epithelial (HEK-293) in vitro. The kinetics of the bioreduction and the influence of pH were examined by an ultraviolet-visible (UV-Vis) spectrophotometer. GNPs were characterized by field emission transmission electron microscopy (FE-TEM), X-ray diffraction (XRD), dynamic light scattering (DLS), and Fourier transform infrared (FTIR) spectroscopy. Ginsenoside loading efficiency of C-K-GNPs and Rh2-GNPs was determined to be approximately 62.83% and 54.91%, respectively, by thermogravimetric analysis (TGA). These results suggest that one-pot synthesis by ginsenosides C-K and Rh2 may be useful for producing ginsenoside-loaded gold nanocarriers.

Why can a gold salt react as a base?

Why can a gold salt react as a base?

Reductant-free synthesis of magnetoplasmonic iron oxide-gold nanoparticles

Stable suspensions of spherical 10–15 nm superparamagnetic iron oxide nanoparticles (SPIONs) have been synthetized by co-precipitation, stabilized with citric acid, surface functionalized with aminopropyltriethoxysilane (APTES) and finally decorated with ultra-small gold nanoparticles (GNPs) by in situ reduction of a soluble gold salt (HAuCl4), obtaining well dispersed SPIONs-GNPs colloids. The morphology, size and stability of the SPIONs-GNPs suspensions have been controlled by adjusting the molar ratio of the reagents (Fe/HAuCl4 and Fe/APTES). The synthesis route differs from that typically found in literature, using tunable chelating layer modifications (such as citric acid and –NH2 groups) of the magnetic core, depositing GNPs on the amine-functionalized iron oxide surface without the use of a specific reducing agent, and tuning the process pH and temperature. An explanation of how the different chemical species involved in the synthesis route could be responsible for the reducing action has been provided. The SPIONs-GNPs colloids have been characterized after each synthesis step by Transmission Electron Microscopy (TEM), Scanning Transmission Electron Microscopy (STEM), energy-dispersive X-ray spectroscopy (EDXS), Fourier transform infrared spectroscopy (FTIR), ζ Potential measurements, magnetic measurements with a vibrating-sample magnetometer (VSM) and UV–VIS spectroscopy. The SPIONs-GNPs colloids showed magnetoplasmonic behaviors since they maintained the plasmonic properties of GNPs and the superparamagnetic response of iron oxide NPs.

Macrophage Activation Syndrome in Systemic Juvenile Idiopathic Arthritis

One of the complications of systemic juvenile idiopathic arthritis (SJIA) is macrophage activation syndrome (MAS), which may be considered as a form of secondary haemophagocytic lymphohistiocytosis. Trigger factors are drugs (aspirin, nonsteroidal anti-inflammatory drugs, gold preparations, methotrexate, and tumour necrosis factor blocking agents), drug change, drug side effects, or initiation of biological drugs and infections. The pathogenesis of MAS is still unclear and it may be explained by uncontrolled activities of macrophages. A lot of proinflammatory cytokines such as tumour necrosis factor-α, interleukin (IL)-1, IL-6, and interferon gamma play important roles in the pathogenesis of MAS. The diagnosis of MAS is often challenging. In 2016, the European League Against Rheumatism/American College of Rheumatology (EULAR/ACR) approved classification criteria for MAS complicating SJIA. Corticosteroid and cyclosporin A treatment have been used in the treatment of MAS. Intravenous immunoglobulin treatment has been used in some cases of MAS. Biologic agents have been used, such as anakinra (IL-1 alpha and beta inhibition), canakinumab (IL-1 beta inhibition), and tocilizumab (IL-6 inhibition). Early detection and early intervention are vital to avoid poor outcomes in MAS. SJIA is a subtype of juvenile idiopathic arthritis, and MAS is a serious, potentially fatal, complication of SJIA that occurs most commonly in children.