Presence Of Gold Nanoparticles Research Articles

Efficient removal of environmental pollutants by green synthesized metal nanoparticles of Clitoria ternatea

Prevention and management of water pollution are becoming a great challenge in the present scenario. Different conventional methods like carbon adsorption, ion exchange, chemical precipitation, evaporation, and biological treatments remove water pollutants. Nowadays, the requirement for effective, non-toxic and safe waste management strategies is very high. Nanomaterials have been explored in various fields due to their unique characteristics. Green synthesis of nanomaterial is becoming more popular due to their safety, non-toxicity, and ease of scale-up technology. Metal nanoparticles can be synthesized using a green synthesis method using biological sources provided by eco-friendly, non-hazardous nanomaterials with superior properties to bulk metals. Hence, this study has designed a green synthesis of magnetic (cobalt oxide) and noble (gold) nanoparticles from the fresh flowers of Clitoria ternatea. The flavonoids and polyphenols in the extract decreased the energy band gap of cobalt oxide and gold nanoparticles; hence, the capping of the natural constituents in Clitoria ternatea helped form stable metal nanoparticles. The cobalt oxide and gold nanoparticles are evaluated for their potential for eliminating organic pollutants from industrial effluent. The novelty of this present work represents the application of cobalt oxide nanoparticles in the removal of organic pollutants and a comparative study of the catalytic behaviour of both metal nanoparticles. The degradation of bromophenol blue, bromocresol green, and 4–nitrophenol in the presence of gold nanoparticles was completed in 120, 45, and 20 min with rate constants of 3.7 × 10−3/min, 6.9 × 10−3/min, and 16.5 × 10−3/min, respectively. Similarly, the photocatalysis of bromophenol blue, bromocresol green, and 4–nitrophenol in the presence of cobalt oxide nanoparticles was achieved in 60, 90, and 40 min with rate constants of 2.3 × 10−3/min, 1.8 × 10−3/min, and 1.7 × 10−3/min, respectively. The coefficient of correlation (R2) values justify that the degradation of organic pollutants follows first-order kinetics. The significance of the study is to develop green nanomaterials that can be used efficiently to remove organic pollutants in wastewater using a cost-effective method with minimal toxicity to aquatic animals. It has proved to be useful in environmental pollution management.

Enhancing the Green Synthesis of Glycerol Carbonate: Carboxylation of Glycerol with CO2 Catalyzed by Metal Nanoparticles Encapsulated in Cerium Metal-Organic Frameworks.

The reaction of glycerol with CO2 to produce glycerol carbonate was performed successfully in the presence of gold nanoparticles (AuNPs) supported by a metal-organic framework (MOF) constructed from mixed carboxylate (terephthalic acid and 1,3,5-benzenetricarboxylic acid). The most efficient were two AuNPs@MOF catalysts prepared from pre-synthesized MOF impregnated with Au3+ salt and subsequently reduced to AuNPs using H2 (catalyst 4%Au(H2)@MOF1) or reduced with NaBH4 (catalyst 4%Au@PEI-MOF1). Compared to existing catalysts, AuNPs@MOFs require simple preparation and operate under mild and sustainable conditions, i.e., a much lower temperature and the lowest CO2 overpressure ever reported, with MgCO3 having been found to be the optimal dehydrating agent. Although the yield of the process is still not competitive with previously developed systems, the most promising advantage is the highest TOF (78 h-1) ever reported for this reaction. The optimal parameters observed for AuNPs were also tested on AgNPs and CuNPs with promising results, suggesting their great potential for industrial application. The catalysts were characterized by XRD, TEM, SEM-EDS, ICP-MS, XPS, and porosity measurements, confirming that AuNPs are present in low concentration, uniformly distributed, and confined to the cavities of the MOF.

Electrochemical behavior of Newcastle virus La Sota strain (Newvac vaccine) in the presence of gold nanoparticles as sensitizers investigated on Au electrode

The use of advanced electrochemical methods provides a significant methodological approach to a variety of tasks and research problems in bioelectrochemistry. Of particular importance in terms of bioelectrochemical aspects is the electrochemical behavior of viruses at charged interfaces. The gold electrode is considered ideal for investigating the behavior of biomolecules in aqueous media. Gold nanoparticles (nAu) have unique properties that allow them to be used to facilitate electron transfer between the electrode surface and biomolecules, making them a promising choice as a bioelectrochemical catalyst. The aim of the study is the analysis and physicochemical characterization of the Newcastle virus (NCV) La Sota strain, Newvac vaccine in phosphate buffer solution (PB) using gold nanoparticles as sensitizers. With respect to the electrochemical and electrical parameters, the Au/electrolyte interface constituted a system studied by Open Circuit Potentiometry (OCP), Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS), Square Wave Voltammetry (SWV) and Chronopotentiometry (CP) in association with UV-Vis spectrophotometry. Gold nanoparticles have the role of sensitizing the redox processes in which the La Sota virus participates, as indicated by the amount of charge passing through the interface associated with anodic processes (Qa / Qc) increases from 0.31 (PB), 0.43 (PB-nAu), 0.54 (PB_NCV) to 0.61 (PB_nAu_NCV).

Increase of OH radical yields due to the decomposition of hydrogen peroxide by gold nanoparticles under X-ray irradiation.

We elucidate the decomposition mechanism of hydrogen peroxide, which is formed by water radiolysis, by gold nanoparticles (GNPs) under X-ray irradiation. The variations in yields of hydrogen peroxide generated in the presence of GNPs are evaluated using the Ghormley technique. The increase of yields of OH radicals has been quantified using Ampliflu® Red solutions. Almost all hydrogen peroxide generated by irradiation of <25 Gy is decomposed by GNPs, while the yield of OH radicals increases by 1.6 times. The amount of OH radicals thus obtained is almost equivalent to that of the decomposed hydrogen peroxide. The decomposition of hydrogen peroxide is an essential reaction to produce additional OH radicals efficiently in the vicinity of GNPs.

Indirect effects of interference of two emerging environmental contaminants on cell health: Radiofrequency radiation and gold nanoparticles

BackgroundThe global need for wireless technologies is growing rapidly. So, we have been exposed to a new type of environmental pollution: radiofrequency radiation (RFR). Recent studies have shown that RFR can cause not only direct effects but also indirect or non-targeted effects such as the bystander effect (BE). In this study, we investigated the BE induced by RFR in the present of gold nanoparticles (GNP). Moreover, we studied the expression of cyclooxygenase-2 (COX-2). MethodsNon-toxic dose of 15-nm GNP was used to treat the Chinese Hamster Ovary (CHO) cells. After 48 h of incubation, cells were exposed to 900 MHz GSM RFR for 24 h. Then we collected the cell culture medium of these cells (conditioned culture medium, CCM) and transferred it to new cells (bystander cells). Cell deaths, DNA breaks, oxidative stress and COX-2 expression were analyzed in all groups. ResultsThe results showed that RFR increased metabolic death in cells treated with GNP. Inversely, the colony formation ability was reduced in bystander cells and RFR exposed cells either in the presence or absence of GNP. Also, the level of reactive oxygen species (ROS) in GNP treated cells showed a significant reduction compared to those of untreated cells. However, RFR-induced DNA breaks and the frequencies of micronuclei (MN) were not significantly affected by GNP. The expression of COX-2 mRNA increased in RFR GNP treated cells, but the difference was not significant. ConclusionOur results for the first time indicated that RFR induce indirect effects in the presence of GNP. However, the molecular mediators of these effects differ from those in the absence of GNP. Also, to our knowledge, this is the first study to show that COX-2 is not involved in the bystander effect induced by 900 MHz RFR.

SERS-based pH-Dependent detection of sulfites in wine by hydrogel nanocomposites

Sulfur dioxide (SO2) and sulfites are well-known additives in winemaking due to their preservative properties. Although they can prevent oxidation and inhibit microbial growth, they pose health risks and require limitations on their use. Consequently, the total level of SO2 is regulated and several quantification strategies have been proposed. The approved detection methods require the extraction of SO2 by heating and/or acid treatment. Then, iodine or acid/base titrations are conducted for the detection of liberated SO2. Although these methods can provide sensitive detection of SO2, they are complex, time-consuming, and require sample preparation steps and skilled operators. Thus, to overcome these disadvantages, an easy-to-use method, involving simple sample preparation steps, and offering high sensitivity and selectivity, is desirable. Herein, we introduce a SERS-based strategy for SO2 detection in liquids using hydrogel nanocomposites. The hydrogels are prepared by poly(ethylene glycol) diacrylate (PEGDA) in the presence of gold nanoparticles (AuNPs), acting as the SERS substrate. The use of hydrogels ensures a homogenous signal distribution and an efficient collection of SO2, and drying the hydrogels enhances and stabilizes the obtained SO2 signal. The detection strategy is based on the pH-dependent dissociation of SO2. By adjusting the pH value of wine to 10 through simple dilutions, SO2 can be directly detected in wine, down to 0.4 ppm, well below the regulatory limits. The proposed method allows for sensitive, direct, cost-effective detection of SO2 by eliminating the loss of the gaseous form of the sample and avoids titration-based detection methods.

How Does pH Affect the Adsorption of Human Serum Protein in the Presence of Hydrophobic and Hydrophilic Nanoparticles at Air-Water and Lipid-Water Interfaces?

This study investigates interaction between hydrophilic (11-mercaptoundecanoic acid (MUA)) and hydrophobic (1-undecanethiol (UDT)) gold nanoparticles (GNPs) with human serum albumin (HSA) protein on air-water and lipid-water interfaces at pH 3 and 7. Vibrational sum frequency generation (VSFG) spectroscopy is used to analyze changes in the intensity of interfacial water molecules and the C-H group of the protein. At the air-water interface, the hydrophobic interaction between the HSA protein and hydrophobic GNPs at pH 3 leads to their accumulation at the interface, resulting in an increased C-H intensity of the protein with a slight decrease in water intensity. Whereas, at pH 7, where the negative charge of the protein results in the reduced surface activity of the HSA compared to pH 3, the interaction between alkyl chain of the hydrophobic GNPs and alkyl group of the protein results in the adsorption of the protein-capped GNPs at the interface. This leads to an increased intensity of the C-H group of protein and water molecules. However, negatively charged hydrophilic GNPs do not induce significant changes in the interfacial water structure or the C-H group of the protein due to the electrostatic force of repulsion with the negatively charged HSA at pH 7. In contrast, at the lipid-water interface, both hydrophobic and hydrophilic GNPs interact with HSA protein, causing disordering of interfacial water molecules at pH 3 and ordering at pH 7. Interestingly, similar behavior of the protein with both types of GNPs results in comparable ordering/disordering at the interface depending on the pH of solution. Furthermore, the VSFG results obtained with the deuterated lipid suggest that changes in ordering and disorder occur due to increased protein adsorption in the presence of GNPs, causing alterations in the membrane structure. These findings give a better understanding of the mechanisms that govern protein-nanoparticle interaction and their consequential effects on the structure, function, and behavior of molecules at the biological membrane interface, which is crucial for developing safe and effective nanoparticle-based therapeutics.

Bioimaging based on Poly(ethylenimine)-Coated Carbon Dots and Gold Nanoparticles for pH Sensing and Metal Enhanced Fluorescence.

When exposed to specific light wavelengths, carbon dots (CDs), which tend to be fluorescent, can emit colorful light. It provides them with a lot of adaptability for different applications including bioimaging, optoelectronics, and even environmental sensing. Poly(ethylenimine) (PEI) coated carbon dots (PEI-CDs) with a long emission wavelength were synthesized via the hydrothermal method. The resultant CDs show strong fluorescence with quantum yield up to 20.2%. The PEI-CDs exist with distinct pH-sensitive features with pH values in the range of 2-14. The optical characteristics of CDs are pH-responsive due to the presence of different amine groups on PEI, which is a functional polycationic polymer. One of the most widely employed nanoparticles for improving the fluorescence plasmonic characteristics of a nanocomposite is gold. Gold nanoparticles were coupled with PEI-CDs in this assay by using the EDC-NHS coupling to increase the photoluminescence property of the PEI-CDs by using the metal-enhanced fluorescence approach. In the presence of gold nanoparticles, the fluorescence is enhanced 5-6 times. The likely mechanism in our investigation was primarily derived from enhancement of the intrinsic radiative decay rate rather than the local electric field impact. Moreover, PEI-CDs can be used as a bioimaging agent, as these molecules are nontoxic to the cells, and the positively charged PEI-CDs have the potential for nuclear targeting, allowing for electrostatic contact with DNA in the nucleus. This finding will expand the application that the PEI-CDs can be used in the future for targeted imaging applications.

First purported images of ciguatoxin-3C by cryogenic and transmission electron microscopy

Marine biotoxins in seafood products are responsible for human illnesses and seafood production losses. Ciguatera poisoning (CP) is the most commonly reported non-bacterial seafood-related illness worldwide and is caused by the consumption of fish or shellfish containing ciguatoxins (CTXs), a class of polycyclic polyether marine biotoxins with highly complex chemical structures. Reliable laboratory testing in clinical samples for CTXs is not available and many analogues remain structurally unresolved. CTXs have a proposed backbone size of 3 nm but have never been directly observed. Herein, the first purported images of CTX-3C obtained by Cryogenic Electron Microscopy (Cryo-EM) and in the presence of gold nanoparticles with attached antibodies by Transmission Electron Microscopy (TEM) are presented. TEM image was captured based on a sample preparation optimization technique using anti-ciguatoxins CTX-3C [1C49] Ab00350–1.1 purified antibodies, gold nanoparticles, and a concentration of synthetic CTX-3C molecules combined for imaging. We discuss how other existing instrumentations with atomic resolutions exceeding <0.1 nm could be applied using this preparatory method to observe, with greater detail, the common backbone of all known CTXs and its proposed wider adoption towards other marine biotoxins. Conventional detection methods for marine toxins have drawbacks, applying cutting-edge existing technologies such as TEMs to directly observe never-before-seen marine toxins can contribute to the fundamental science of marine toxins research.

Bystander Effect of Sonodynamic Therapy in the presence of Gold Nanoparticles: An in-vitro study

Bystander Effect of Sonodynamic Therapy in the presence of Gold Nanoparticles: An in-vitro study

Investigating the effects of gold and titania nanoparticles in the treatment of breast cancer using a compressed breast phantom in the presence of high intensity low mono-energetic x-ray radiation

Today, with the advancement of nanotechnology, nanomaterials with high atomic numbers such as gold and titania nanoparticles can be specifically concentrated in tumor cells in various ways and benefited from the advantage of increasing the dose due to the proximity of these elements next to cancer cells as a radiation sensitizer. In this research, parameters such as radiation energy (in the range of kilo voltage), nanoparticles concentration, and tumor depth were investigated in the compressed breast phantom by using the MCNPX code to investigate the effect of radio sensitivity. The tumor in the form of a cube with sides of 0.5 cm was labeled with spherical nanoparticles of titania and gold with a radius of 70 nm with different concentrations. The results showed that exposure to the range of kilo voltage causes photoelectric absorption to occur with a high probability and a relatively large dose is delivered to the tumor. The energy that can cause the most damage to the tumor was obtained at 65 keV in the presence of gold nanoparticles and in the range of 40 to 45 keV in the presence of titania nanoparticles. Also, with increasing concentration the dose enhancement factor increases, but with increasing depth, for dose enhancement factor does not change.

Hydrophobicity and FTIR absorbance spectroscopy of Polydimethylsiloxane (PDMS) films treated with aqueous gold nanoparticles (AuNP) solution

Polydimethylsiloxane (PDMS) thin films were treated with aqueous solutions of gold nanoparticles. Samples treated for 24, 48, and 72 h, including untreated PDMS film, were subjected to hydrophobicity test and FTIR absorbance spectroscopy. Hydrophobicity test involved measuring the contact angle of water droplets placed on top of the sample films. Contact angles were measured using Image J software. Treated samples showed significant hydrophobicity changes shown by the increasing value of measured contact angle from 71.3° for the untreated sample to 104.0° for the sample treated for 72 h. FTIR absorbance spectra of the treated sample showed peaks at 3374 cm−1, 3295 cm−1, 2096 cm−1 and 2031 cm−1 with the peak intensity values increasing with corresponding samples of increasing hours of treatment. With the presence of gold nanoparticles on the PDMS film confirmed, the gold nanoparticles may now be functionalized for biosensing and biotesting applications of liquid samples.

Application of the "Plazmontest" Software and Hardware Complex for the Determination of Spermine Concentration

Introduction. One of the main areas of application of SPR sensors is biochemical analysis. The "Plasmontest" device, developed at the Institute of Cybernetics of the National Academy of Sciences of Ukraine, was used for rapid diagnosis of various concentrations of the tumor marker spermine. Colloidal gold nanoparticles stabilized by sodium citrate were used as a sensitive layer for the detection of biogenic polyamines as markers of prostate cancer development. Two methods of conducting an experiment on spermine detection using colloidal gold nanoparticles are proposed. The purpose of the paper is to show the possibility of detecting the tumor marker spermine in different concentrations using the "Plasmontest" device. To solve this problem it is necessary to provide a series of experiments on the application of colloidal gold solutions with different methods of deposition of reagents. The results. With the help of the "Plasmontest" software and technical complex, a series of biochemical experiments were carried out using solutions of spermine in the concentration range of 50 nM - 500 nM and colloidal gold in a concentration of 3·10-4 M. Two methods of applying reagents were proposed: spermine – colloidal gold and colloidal gold – spermine. Both techniques made it possible to observe a shift in the SPR angle, which means the adsorption of spermine on the surface of a gold film with colloidal gold nanoparticles. Conclusions. It is shown that the developed software and technical complex "Plasmontest" allows monitoring the course of biochemical reactions at low concentrations of the investigated reagents. Studies of the possibility of detecting spermine in different concentrations in the presence of gold nanoparticles using the PPR method open the prospect of creating a biosensor for spermine. Keywords: surface plasmon resonance, biosensor, nanoparticles, spermine.

The sensitivity enhancement of TiO2-based VOCs sensor decorated by gold at room temperature

Detection of hazardous toxic gases for air pollution monitoring and medical diagnosis has attracted the attention of researchers in order to realize sufficiently sensitive gas sensors. In this paper, we fabricated and characterized a Titanium dioxide (TiO2)-based gas sensor enhanced using the gold nanoparticles. Thermal oxidation and sputter deposition methods were used to synthesize fabricated gas sensor. X-ray diffraction analysis was used to determine the anatase structure of TiO2 samples. It was found that the presence of gold nanoparticles on the surface of TiO2 enhances the sensitivity response of gas sensors by up to about 40%. The fabricated gas sensor showed a sensitivity of 1.1, 1.07 and 1.03 to 50 ppm of acetone, methanol and ethanol vapors at room temperature, respectively. Additionally, the gold nanoparticles reduce 50 s of response time (about 50% reduction) in the presence of 50 ppm ethanol vapor; and we demonstrated that the recovery time of the gold decorated TiO2 sensor is less than 40 s. Moreover, we explain that the improved performance depends on the adsorption-desorption mechanism, and the chemical sensitization and electronic sensitization of gold nanoparticles.

Nanostructured poly(thiophene acetic acid)/Au/poly(methylene blue) interface for electrochemical immunosensing of p53 protein.

A poly(thiophene acetic acid)/Au/poly(methylene blue) nanostructured interface was electrochemically assembled step-by-step on screen-printed carbon electrodes (SPCE) for label-free detection of p53 protein. The initial electrical conductive properties of the polymeric interface were increased with an additional layer of poly(methylene blue) electropolymerized in the presence of gold nanoparticles. The nano-immunosensing architecture was prepared by covalent immobilization of anti-p53 antibodies as bioreceptors through the poly(thiophene acetic acid) moieties. The nano-immunosensor assembly was extensively characterized by ultraviolet-visible spectrophotometry, dynamic and electrophoretic light scattering, scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, atomic force microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. Under optimal conditions, p53 was specifically and selectively detected by square wave voltammetry in a linear range between 1 and 100ngmL-1 with a limit ofdetection of 0.65ngmL-1. In addition, the electrochemical nano-immunosensor detected p53 in spiked human serum samples and colorectal cancer cell lysates, and the results were validated with a standard spectrophotometric method using a paired samples t test, which did not exhibit significant differences between both methods. The resultant p53 nano-immunosensor is simple to assemble, robust, and has the potential for point-of-care biomarker detection applications.

Determining the impact of gold nanoparticles on amyloid aggregation with 2D IR spectroscopy.

As nanomaterials become more prevalent in both industry and medicine, it is crucial to fully understand their health risks. One area of concern is the interaction of nanoparticles with proteins, including their ability to modulate the uncontrolled aggregation of amyloid proteins associated with diseases, such as Alzheimer's disease and type II diabetes, and potentially extend the lifetime of cytotoxic soluble oligomers. This work demonstrates that two-dimensional infrared spectroscopy and 13C18O isotope labeling can be used to follow the aggregation of human islet amyloid polypeptide (hIAPP) in the presence of gold nanoparticles (AuNPs) with single-residue structural resolution. 60nm AuNPs were found to inhibit hIAPP, tripling the aggregation time. Furthermore, calculating the actual transition dipole strength of the backbone amide I' mode reveals that hIAPP forms a more ordered aggregate structure in the presence of AuNPs. Ultimately, such studies can provide insight into how mechanisms of amyloid aggregation are altered in the presence of nanoparticles, furthering our understanding of protein-nanoparticle interactions.

Tunable Magneto-Plasmonic Nanosensor for Sensitive Detection of Foodborne Pathogens

Frequent outbreaks of food-borne pathogens, particularly E. coli O157:H7, continue to impact human health and the agricultural economy tremendously. The required cell count for this pathogenic strain of E. coli O157:H7 is relatively low and hence it is vital to detect at low colony forming unit (CFU) counts. Available detection methods, though sensitive, fall short in terms of timeliness and often require extensive sample processing. To overcome these limitations, we propose a novel magneto-plasmonic nanosensor (MPnS) by integrating surface plasmon resonance (SPR) properties with spin-spin magnetic relaxation (T2 MR) technology. We engineered MPnS by encapsulating several gold nanoparticles (GNPs) within the polymer-coating of iron oxide nanoparticles (IONPs). First, the polyacrylic acid (PAA)-coated IONPs were synthesized using a solvent precipitation method, then gold chloride solution was used to synthesize GNPs and encapsulate them within the PAA-coatings of IONPs in one step. A magnetic separation technique was used to purify the MPnS and the presence of GNPs within IONPs was characterized using transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS), and other spectroscopic methods. The synthesized MPnS exhibits MR relaxation properties while possessing amplified optical properties than conventional GNPs. This allows for rapid and ultrasensitive detection of E. coli O157:H7 by SPR, T2 MR, and colorimetric readout. Experiments conducted in simple buffer and in milk as a complex media demonstrated that our MPnS-based assay could detect as low as 10 CFUs of this pathogenic strain of E. coli O157:H7 in minutes with no cross-reactivity. Overall, the formulated MPnS is robust and holds great potential for the ultrasensitive detection of E. coli O157:H7 in a simple and timely fashion. Moreover, this platform is highly customizable and can be used for the detection of other foodborne pathogens.

Физико-химические свойства наночастиц золота в рудах и катализаторах

Introduction. At present, in the instrumental study of the mineral forms of finding gold in geogenic and technogenic ores, more and more attention has been paid to free gold, with a size of several nanometers. Such gold has been found in almost all types of its geogenic ores: starting with deposits of primary sulfide ores and ending with various gold-bearing placers. A similar situation is observed with technogenic gold-bearing ores accumulated in numerous dumps and tailings. At the same time, with the increase in research on nanogold, not only its fundamental, but also practical importance grows, because. in theoretical and applied research, more and more of its actual physical and chemical properties and previously unknown phenomena and effects accompanying them are discovered and clarified. Research methods and materials. An important aspect is the instrumental study of the geometry of various forms of nanogold occurrence in natural (geogenic) and technogenic ores and minerals. The instrumental and analytical part of our research was based on the visualization of nanoparticles obtained from the Nanjing Research Institute of the Chemical Industry under Sinopec (PRC), carried out on a JEOL 2010F microscope. Research results. The studied gold nanoparticles were presented in the form: • spherical fullerene-like monoparticles; • fullerene-like gold cells, consisting of a different number (from 13 to 20 clusters) of gold nanoparticles; • self-organized «fractal» dendrites; • rather complex composites with the participation of nanogold; • various aggregates of nanoparticles, etc. The concentrations of gold nanoparticles vary significantly from one deposit to another and between individual ore facies (even within the same deposit). Discussion of the obtained results. It was found that nanogold can be contained in arsenopyrites in 2 main forms: a) as a structurally bound solid solution (Au + 1) located in the lattice of this mineral; b) in separate mineral inclusions of submicron size or nanoparticles. Gold nanoparticles (5-10 nm in size) detected in arsenopyrite in concentrations up to 4% mass fraction are sufficiently representative to account for their amount in gold-bearing ores. A gold nanoparticle with a size of 3 nm usually has an average coordination number CN = 9.5, similar nanoparticles with a size of 1 nm have an average CN = 6, and nanoparticles with a size of 0.5–1 nm have an average CN = 3.6. Conclusion. To date, a nanoparticle catalyst has been developed in which gold clusters are attached to metal oxides that are semiconductors. At the same time, their number is very limited and includes only Fe2O3, TiO2, CeO2, and MgO compounds, which can be used not only in the form of nanoparticles, but also nanofilms. Such an innovative nanocatalyst ensures the efficient flow of a number of oxidative and other processes with hydrocarbons at normal temperatures, which is difficult to achieve by other methods. Findings. The article presents the results of studies of the physicochemical properties of gold nanoparticles installed in ores and catalysts. The morphology of gold nanoparticles has been established. The character of gold speciation in various sulfides is determined. The presence of gold nanoparticles in ores and rocks in the state of colloids has been confirmed. The catalytic activity of nanoparticles of various shapes and chemical states was revealed, depending on the values of the ambient temperature. The results of the research can be useful in the enrichment of gold-bearing ores of upland deposits.

Engineering Geobacter pili to produce metal:organic filaments

The organized self-assembly of conductive biological structures holds promise for creating new bioelectronic devices. In particular, Geobacter sulfurreducens type IVa pili have proven to be a versatile material for fabricating protein nanowire-based devices. To scale the production of conductive pili, we designed a strain of Shewanella oneidensis that heterologously expressed abundant, conductive Geobacter pili when grown aerobically in liquid culture. S. oneidensis expressing a cysteine-modified pilin, designed to enhance the capability to bind to gold, generated conductive pili that self-assembled into biohybrid filaments in the presence of gold nanoparticles. Elemental composition analysis confirmed the filament-metal interactions within the structures, which were several orders of magnitude larger than previously described metal:organic filaments. The results demonstrate that the S. oneidensis chassis significantly advances the possibilities for facile conductive protein nanowire design and fabrication.

Printed Electrochemical Strip for the Detection of miRNA-29a: A Possible Biomarker Related to Alzheimer's Disease.

The development of electrochemical strips, as extremely powerful diagnostic tools, has received much attention in the field of sensor analysis and, in particular, the detection of nucleic acids in complex matrixes is a hot topic in the electroanalytical area, especially when directed toward the development of emerging technologies, for the purpose of facilitating personal healthcare. One of the major diseases for which early diagnosis is crucial is represented by Alzheimer's disease (AD). AD is a progressive neurodegenerative disease, and it is the most common cause of dementia worldwide. In this context microRNAs (miRNAs), which are small noncoding RNAs, have recently been highlighted for their promising role as biomarkers for early diagnosis. In particular, miRNA-29 represents a class of miRNAs known to regulate pathogenesis of AD. In this work we developed an electrochemical printed strip for the detection of miRNA-29a at low levels. The architecture was characterized by the presence of gold nanoparticles (AuNPs) and an anti-miRNA-29a probe labeled with a redox mediator. The novel analytical tool has been characterized with microscale thermophoresis and electrochemical methods, and it has been optimized by selection of the most appropriate probe density to detect low target concentration. The present tool was capable to detect miRNA-29a both in standard solution and in serum, respectively, down to 0.15 and 0.2 nM. The platform highlighted good repeatability (calculated as the relative standard deviation) of ca. 10% and satisfactory selectivity in the presence of interfering species. This work has the objective to open a way for the study and possible early diagnosis of a physically and socially devastating disease such as Alzheimer's. The results demonstrate the suitability of this approach in terms of ease of use, time of production, sensitivity, and applicability.