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The recovery and valorization of metals and rare earth metals from wastewater are of great importance to prevent environmental pollution and recover valuable resources. Certain bacterial and fungal species are capable of removing metal ions from the environment by facilitating their reduction and precipitation. Even though the phenomenon is well documented, little is known about the mechanism. Therefore, we systematically investigated the influence of nitrogen sources, cultivation time, biomass, and protein concentration on silver reduction capacities of cell‐free cultivation media (spent media) of Aspergillus niger, A. terreus, and A. oryzae. The spent medium of A. niger showed the highest silver reduction capacities with up to 15 μmol per milliliter spent medium when ammonium was used as the sole N‐source. Silver ion reduction in the spent medium was not driven by enzymes and did not correlate with biomass concentration. Nearly full reduction capacity was reached after 2 days of incubation, long before the cessation of growth and onset of the stationary phase. The size of silver nanoparticles formed in the spent medium of A. niger was influenced by the nitrogen source, with silver nanoparticles formed in nitrate or ammonium‐containing medium having an average diameter of 32 and 6 nm, respectively. [ABSTRACT FROM AUTHOR]

Poly‐1‐vinyl‐1,2,4‐triazole (PVT)‐based materials with silver nanoparticles are promising antibacterial products. The metal nanoparticles with controllable sizes were obtained by radiation‐induced reduction of the dispersions of complexes of PVT with silver ions. Formation of the silver nanoparticles in aqueous suspensions irradiated at pH 6.0, 2.5, and 2.0 was studied using methods of UV–VIS spectroscopy and transmission electron microscopy. UV–VIS spectroscopy has detected a change in the efficiency of interaction between protonated or non‐protonated PVT units and the surface of silver nanoparticles. The interaction of macromolecules with the metal surface under different degrees of protonation of PVT functional groups afforded the nanoparticles with a narrow size distribution and an average size from 3 to 10 nm. An increase in the acidity also leads to a decrease in the ratio of the generation/growth of nanoparticles. The radiation approaches both provide the synthesis of the nanoparticles of controlled sizes and permits to obtain the nanocomposites containing no impurities of chemical reducing agents. The nanocomposites obtained exhibit high antibacterial activity against various bacterial strains, which depends on the size of silver nanoparticles. [ABSTRACT FROM AUTHOR]

The integration of silver nanoparticles (Ag NPs) with mesoporous silica nanoparticles (MSNs) protects the former from aggregation and promotes the controlled release of silver ions, resulting in therapeutic significance on cancer and infection. The unique size, shape, pore structure and silver distribution of silver mesoporous silica nanoparticles (Ag‐MSNs) embellish them with the potential to perform combined imaging and therapeutic actions via modulating optical and drug release properties. Here, we comprehensively review the recent progress in the fabrication and application of Ag‐MSNs for combination therapies for cancer and infection. We first elaborate on the fabrication of star‐shaped structure, core‐shell structure, and Janus structure Ag‐MSNs. We then highlight Ag‐MSNs as a multifunctional nanoplatform to surface‐enhanced Raman scattering‐based detection, non‐photo‐based cancer theranostics and photo‐based cancer theranostics. In addition, we detail Ag‐MSNs for combined antibacterial therapy via drug delivery and phototherapy. Overall, we summarize the challenges and future perspectives of Ag‐MSNs that make them promising for diagnosis and therapy of cancer and infection. [ABSTRACT FROM AUTHOR]

In this study silver nanoparticles were dispersed over polyaniline nanofibers (nPANI) by simple chemical reduction of silver nitrate in the presence of nPANI, and the prepared nPANI/Ag nanocomposite was employed for sensitive and cost‐effective non‐enzymatic detection of glucose using a modified carbon paste electrode. Detailed structural, crystallographic and morphological characterization of nPANI/Ag was carried out by means of Fourier‐transform infrared spectroscopy, X‐ray diffractometry and scanning electron microscopy. The enhancement of charge transfer of nPANI upon incorporation of Ag nanoparticles was confirmed by electrochemical impedance spectroscopy, and the electrocatalytic efficacy of the nPANI/Ag nanocomposite towards oxidation of glucose in alkaline medium was proven by cyclic voltammetry. Crucially, chronoamperometry demonstrated a linear response of the nPANI/Ag‐based glucose sensor over a wide range of glucose concentrations from 100 μM to 10 mM with a lowest detection limit of 1,3 μM. The sensor had a good selectivity for glucose in the presence of common interfering biomolecules. The sensor also had a shelf‐life of several days and the response was repeatable for up to nine individual measurements. [ABSTRACT FROM AUTHOR]

Poly(styrene@N‐isopropylmethacrylamide‐methacrylic acid) [P (St‐NM)] microgels were prepared via seed facilitated emulsion polymerization process. In situ reduction of silver ions was carried out to generate Ag nanoparticles in the voids of shell region of polymer microgels. Synthesized P (St‐NM) and Ag‐P (St‐NM) particles were characterized by UV–Vis spectroscopy, transmission electron microscopy (TEM), Fourier‐transformed infrared spectroscopy (FTIR), and X‐ray diffraction (XRD). The stability of Ag nanoparticles within P (St‐NM) system over the wide range of pH and temperature is also a part of this study. Thus, prepared Ag‐P (St‐NM) was tested for its catalytic efficiency against reduction of K2Cr2O7 using formic acid (FA) as reductant. Factors affecting catalytic efficiency of Ag‐P (St‐NM) system towards transformation of Cr+6 to Cr+3 were investigated. Other toxic chemicals can also be reduced using same catalytic system. [ABSTRACT FROM AUTHOR]

This study employed NMR metabolomics to characterize macrophage responses to subtoxic concentrations of silver nanoparticles (AgNPs ca. 30 nm) and ionic silver (Ag+), with a view to further elucidate their immunomodulatory activity at the cell metabolism level. Exposure to AgNPs caused RAW 264.7 macrophages to decrease intracellular glucose utilization, possibly due to interference with glycolytic enzymes, and to reprogram the TCA cycle towards anaplerotic fueling and production of anti‐inflammatory metabolites (e.g. itaconate and creatine). Moreover, AgNPs‐exposed cells were able to control the levels of reactive oxygen/nitrogen species (ROS/RNS), likely through upregulation of glutathione synthesis. On the other hand, macrophages exposed to Ag+ at equivalent subtoxic concentrations showed reduced metabolic activity, lower ability to counterbalance ROS/RNS and alterations in membrane‐related lipids. Overall, the metabolomics approach hereby employed provided novel insights into the differential effects of AgNPs and Ag+, which help explain the lower toxic potential of nanosilver than silver ions. [ABSTRACT FROM AUTHOR]

Non‐spherical Au/Ag nanoparticles can be generated by chemical reduction of silver ions in the presence of preformed gold nanoparticles. The process of particle formation can be controlled by concentrations of ligands and reducing agent. The formation of ellipsoidal, nanorod‐ and peanut‐shaped nanoparticles as well as of more complex fractal nanoassemblies can be explained by changes in particle surface state, electrochemical potential formation and particle‐internal self‐polarization effects. It is possible to create highly fractal nanoassemblies with sizes between the mid‐nanometer and the lower micrometer range. The assemblies are marked by high optical absorption and complex nano‐networks of very high surface‐to‐volume ratios and a granular base structure. [ABSTRACT FROM AUTHOR]

Recently the use of medicinal plants potential in the production of nanoparticles has received serious attention. Here, the main component of Camellia sinensis L. (green tea) extract was detected by spectroscopy and the optimal conditions were determined for their performance in green synthesis of silver nanoparticles at room temperature. Epigallocatechin gallate was identified as the dominant component in the extract as determined by spectroscopy, and it was established that its oxidation was a function of the solution pH. Transmission electron microscopy, dynamic light scattering, and visible absorption spectroscopy (UV‐Vis) confirmed the reduction in silver ions to silver nanoparticles (Ag NPs). Controlling over Ag NPs shape and narrow size distribution was achieved with 10 ml green tea leaf extract solution and in different reaction pH. Spherical colloidal Ag NPs with well‐defined hydrodynamic diameters (with average hydrodynamic size of 27.9–50.2 nm) were produced. Silver nitrate concentrations used in this study were lower than that of reported in similar works, and synthesis efficiency was also higher. Nanoparticles were perfectly spherical and their uniformity, compared to similar studies, was much higher. These NPs showed higher degree of stability and were aqueously stable for >10 months in dark glasses at 4°C. [ABSTRACT FROM AUTHOR]

Green tea extract having many phenolic hydroxyl and carbonyl functional groups in its molecular framework can be used in the modification of Fe3O4 nanoparticles. Moreover, the feasibility of complexation of polyphenols with silver ions in aqueous solution can improve the surface properties and capacity of the Fe3O4@green tea extract nanoparticles (Fe3O4@GTE NPs) for sorption and reduction of silver ions. Therefore, the novel Fe3O4@GTE NPs nano-sorbent has potential ability as both reducing and stabilizing agent for immobilization of silver nanoparticles to make a novel magnetic silver nanocatalyst (Fe3O4@GTE/Ag NPs). Inductively coupled plasma analysis, transmission and scanning electron microscopies, energy-dispersive X-ray and Fourier transform infrared spectroscopies, and vibrating sample magnetometry were used to characterize the catalyst. Fe3O4@GTE/Ag NPs shows high catalytic activity as a recyclable nanocatalyst for the reduction of 4-nitrophenol at room temperature. [ABSTRACT FROM AUTHOR]

Current bioavailability models, such as the free ion activity model and biotic ligand model, explicitly consider that metal exposure will be mainly to the dissolved metal in ionic form. With the rise of nanotechnology products and the increasing release of metal-based nanoparticles (NPs) to the environment, such models may increasingly be applied to support risk assessment. It is not immediately clear, however, whether the assumption of metal ion exposure will be relevant for NPs. Using an established approach of oral gluing, a toxicokinetics study was conducted to investigate the routes of silver nanoparticles (AgNPs) and Ag+ ion uptake in the soil-dwelling earthworm Lumbricus rubellus. The results indicated that a significant part of the Ag uptake in the earthworms is through oral/gut uptake for both Ag+ ions and NPs. Thus, sealing the mouth reduced Ag uptake by between 40% and 75%. An X-ray analysis of the internal distribution of Ag in transverse sections confirmed the presence of increased Ag concentrations in exposed earthworm tissues. For the AgNPs but not the Ag+ ions, high concentrations were associated with the gut wall, liver-like chloragogenous tissue, and nephridia, which suggest a pathway for AgNP uptake, detoxification, and excretion via these organs. Overall, the results indicate that Ag in the ionic and NP forms is assimilated and internally distributed in earthworms and that this uptake occurs predominantly via the gut epithelium and less so via the body wall. The importance of oral exposure questions the application of current metal bioavailability models, which implicitly consider that the dominant route of exposure is via the soil solution, for bioavailability assessment and modeling of metal-based NPs. Environ Toxicol Chem 2015;34:2263-2270. © 2015 SETAC [ABSTRACT FROM AUTHOR]

Sphingomonas is a novel and abundant microbial resource for biodegradation of aromatic compounds. It has great potential in environment protection and industrial production. The use of microorganisms for the synthesis of nanoparticles is in the limelight of modern nanotechnology, since it is cost effective, non‐toxic and friendly to the ever‐overwhelmed environment. In this paper, the biosynthesis of silver nanoparticles (AgNPs) using Sphingomonas paucimobilis sp. BDS1 under ambient conditions was investigated for the first time. Biosynthesised AgNPs were characterised with powder ultraviolet–visible spectroscopy, X‐ray diffraction, Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy and energy dispersive X‐ray spectroscopy. The overall results revealed that well‐dispersed face centred cubic spherical AgNPs in the range of 50–80 nm were produced on the surface of Sphingomonas paucimobilis sp. BDS1, after challenging pure wet biomass with silver nitrate solution. This suggests that the capture of silver ions may be a complex process of physical and chemical adsorption and the proteins on the surface of the bacteria may play the role of reduction and stabilising agent with regard to the result of FTIR. [ABSTRACT FROM AUTHOR]

Extracellular and intracellular biosynthesis of silver nanoparticles (AgNPs) by Euglena gracilis (EG) strain and Euglena intermedia (EI) strain are reported in this study. The obtained nanoparticles showed an absorption peak approximates 420 nm in the UV–visible spectrum, corresponding to the plasmon resonance of AgNPs. According to the result of inductively coupled plasma‐atomic emission spectrometer, the intakes of silver ions by EI and EG are roughly equal. The transmission electron microscope (TEM) analysis of the successful in vivo and in vitro synthesised AgNPs indicated the sizes, ranging from 6 to 24 nm and 15 to 60 nm in diameter, respectively, and a spherical‐shaped polydispersal of the particles. The successful formation of AgNPs has been confirmed by energy dispersive X‐ray analysis connected to the TEM. The Fourier transform infrared spectroscopy measurements reveal the presence of bioactive functional groups such as amines are found to be the capping and stabilising agents of nanoparticles. To our knowledge, this is the first report where two kinds of Euglena microalga were used as the potential source for in vivo and in vitro biosynthesis of AgNPs. [ABSTRACT FROM AUTHOR]

A novel silver metallic β‐cyclodextrin (β‐CD)‐core star methoxypolyethylene glycol (mPEG) (SM‐CD‐SPEG) is presented. For this, a well‐defined water‐soluble β‐CD‐core star mPEG with aldehyde groups (CD‐star(ald)PEG, III) is first designed and synthesized via the copper‐catalyzed azide–alkyne click reaction. Then, silver nanoparticles are formed within III through the oxidation–reduction reaction between the aldehyde groups and silver ions. The oxidation–reduction reaction is characterized by means of 1H NMR spectra. And the preparation conditions of SM‐CD‐SPEG are optimized. The resulting SM‐CD‐SPEG aqueous solutions exhibit good stability and a unimolecular micelle morphology. Significantly, it is able to obtain solid SM‐CD‐SPEG samples with molecular water‐solubility. This is convenient for storage and further application of SM‐CD‐SPEG. The SM‐CD‐SPEG samples also show good catalytic performance toward the reduction reaction of methylene blue (MB) by sodium borohydride (NaBH4). [ABSTRACT FROM AUTHOR]