High magnetisation, monodisperse and water-dispersible CoFe@Pt core/shell nanoparticles

High magnetisation and monodisperse CoFe alloy nanoparticles are desired for a wide range of biomedical applications. However, these CoFe nanoparticles are prone to oxidation, resulting in the deterioration of their magnetic properties. In the current work, CoFe alloy nanoparticles were prepared by thermal decomposition of cobalt and iron carbonyls in organic solvents at high temperatures. Using a seeded growth method, we successfully synthesised chemically stable CoFe@Pt core/shell nanostructures. The obtained core/shell nanoparticles have high saturation magnetisation up to 135 emu g−1. The magnetisation value of the core/shell nanoparticles remains 93 emu g−1 after being exposed to air for 12 weeks. Hydrophobic CoFe@Pt nanoparticles were rendered water-dispersible by encapsulating with poly(maleic anhydride-alt-1-octadecene) (PMAO). These nanoparticles were stable in water for at least 3 months and in a wide range of pH from 2 to 11

DMSA-coated cubic iron oxide nanoparticles as potential therapeutic agents

AIM: Superparamagnetic cubic iron oxide nanoparticles (IONPs) were synthesized and functionalized with meso-2,3-dimercaptosuccinic acid (DMSA) as a potential agent for cancer treatment. METHODS: Monodisperse cubic IONPs with a high value of saturation magnetization were synthesized by thermal decomposition method and functionalized with DMSA via ligand exchange reaction, and their cytotoxic effects on HeLa cells were investigated. RESULTS: DMSA functionalized cubic IONPs with an edge length of 24.5 ± 1.9 nm had a specific absorption rate value of 197.4 W/gFe (15.95 kA/m and 488 kHz) and showed slight cytotoxicity on HeLa cells when incubated with 3.3 × 10^{10}, 6.6 × 10^{10} and 9.9 × 10^{10} NP/mL for 24, 48 and 72 h. CONCLUSION: To the best of our knowledge, this is the first study to investigate both the cytotoxic effects of DMSA-coated cubic IONPs on HeLa cells and hyperthermia performance of these nanoparticles

Dimpled SiO₂@γ-Fe₂O₃ nanocomposites – fabrication and use for arsenic adsorption in aqueous medium

We report the synthesis of nanocomposites made of silica nanoparticles whose six surface dimples are decorated with magnetic maghemite nanoparticles and their use for detection and recovery of arsenic in aqueous media. Precursor silica nanoparticles have aminated polystyrene chains at the bottom of their dimples and the maghemite nanoparticles are surface functionalized with carboxylic acid groups in two steps: amination with 3-aminopropyltrimethoxysilane, then derivatization with succinic anhydride in the presence of triethylamine. In the end, the colloidal assembly consists of the regioselective grafting of the carboxylic acid-modified iron oxide nanoparticles onto the 6-dimple silica nanoparticles. Several characterization techniques such as transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) are employed to assess the grafting process and study the influence of the maghemite functional groups on the quality of the composites formed. The resulting magnetic nanocomposites are used for the environmentally benign detection and removal of arsenic from aqueous medium, being readily extracted through means of magnetic separation

A titanium dioxide/nitrogen-doped graphene quantum dot nanocomposite to mitigate cytotoxicity: synthesis, characterisation, and cell viability evaluation

Titanium dioxide nanoparticles (TiO2 NPs) have attracted tremendous interest owing to their unique physicochemical properties. However, the cytotoxic effect of TiO2 NPs remains an obstacle for their wide-scale applications, particularly in drug delivery systems and cancer therapies. In this study, the more biocompatible nitrogen-doped graphene quantum dots (N-GQDs) were successfully incorporated onto the surface of the TiO2 NPs resulting in a N-GQDs/TiO2 nanocomposites (NCs). The effects of the nanocomposite on the viability of the breast cancer cell line (MDA-MB-231) was evaluated. The N-GQDs and N-GQDs/TiO2 NCs were synthesised using a one- and two-pot hydrothermal method, respectively while the TiO2 NPs were fabricated using microwave-assisted synthesis in the aqueous phase. The synthesised compounds were characterised using Fourier transform infrared (FTIR) spectroscopy, high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM) and UV-visible spectrophotometry. The cell viability of the MDA-MB-231 cell line was determined using a CellTiter 96® AQueous One Solution Cell Proliferation (MTS) assay. The obtained results indicated that a monodispersed solution of N-GQDs with particle size 4.40 ± 1.5 nm emitted intense blue luminescence in aqueous media. The HRTEM images clearly showed that the TiO2 particles (11.46 ± 2.8 nm) are square shaped. Meanwhile, TiO2 particles were located on the 2D graphene nanosheet surface in N-GQDs/TiO2 NCs (9.16 ± 2.4 nm). N-GQDs and N-GQDs/TiO2 NCs were not toxic to the breast cancer cells at 0.1 mg mL−1 and below. At higher concentrations (0.5 and 1 mg mL−1), the nanocomposite was significantly less cytotoxic compared to the pristine TiO2. In conclusion, this nanocomposite with reduced cytotoxicity warrants further exploration as a new TiO2-based nanomaterial for biomedical applications, especially as an anti-cancer strategy

Search for Exotic Strange Quark Matter in High Energy Nuclear Reactions

We report on a search for metastable positively and negatively charged states of strange quark matter in Au+Pb reactions at 11.6 A GeV/c in experiment E864. We have sampled approximately six billion 10% most central Au+Pb interactions and have observed no strangelet states (baryon number A < 100 droplets of strange quark matter). We thus set upper limits on the production of these exotic states at the level of 1-6 x 10^{-8} per central collision. These limits are the best and most model independent for this colliding system. We discuss the implications of our results on strangelet production mechanisms, and also on the stability question of strange quark matter.Comment: 21 pages, 9 figures, to be published in Nuclear Physics A (Carl Dover memorial edition

Modeling recursive RNA interference.

An important application of the RNA interference (RNAi) pathway is its use as a small RNA-based regulatory system commonly exploited to suppress expression of target genes to test their function in vivo. In several published experiments, RNAi has been used to inactivate components of the RNAi pathway itself, a procedure termed recursive RNAi in this report. The theoretical basis of recursive RNAi is unclear since the procedure could potentially be self-defeating, and in practice the effectiveness of recursive RNAi in published experiments is highly variable. A mathematical model for recursive RNAi was developed and used to investigate the range of conditions under which the procedure should be effective. The model predicts that the effectiveness of recursive RNAi is strongly dependent on the efficacy of RNAi at knocking down target gene expression. This efficacy is known to vary highly between different cell types, and comparison of the model predictions to published experimental data suggests that variation in RNAi efficacy may be the main cause of discrepancies between published recursive RNAi experiments in different organisms. The model suggests potential ways to optimize the effectiveness of recursive RNAi both for screening of RNAi components as well as for improved temporal control of gene expression in switch off-switch on experiments

A new anode material for oxygen evolution in molten oxide electrolysis

Molten oxide electrolysis (MOE) is an electrometallurgical technique that enables the direct production of metal in the liquid state from oxide feedstock and compared with traditional methods of extractive metallurgy offers both a substantial simplification of the process and a significant reduction in energy consumption. MOE is also considered a promising route for mitigation of CO[subscript 2] emissions in steelmaking, production of metals free of carbon, and generation of oxygen for extra-terrestrial exploration. Until now, MOE has been demonstrated using anode materials that are consumable (graphite for use with ferro-alloys and titanium) or unaffordable for terrestrial applications (iridium for use with iron). To enable metal production without process carbon, MOE requires an anode material that resists depletion while sustaining oxygen evolution. The challenges for iron production are threefold. First, the process temperature is in excess of 1,538 degrees Celsius. Second, under anodic polarization most metals inevitably corrode in such conditions. Third, iron oxide undergoes spontaneous reduction on contact with most refractory metals and even carbon. Here we show that anodes comprising chromium-based alloys exhibit limited consumption during iron extraction and oxygen evolution by MOE. The anode stability is due to the formation of an electronically conductive solid solution of chromium(iii) and aluminium oxides in the corundum structure. These findings make practicable larger-scale evaluation of MOE for the production of steel, and potentially provide a key material component enabling mitigation of greenhouse-gas emissions while producing metal of superior metallurgical quality.American Iron and Steel Institut

Animated molecular dynamics simulations of hydrated caesium-smectite interlayers

Computer animation of center of mass coordinates obtained from 800 ps molecular dynamics simulations of Cs-smectite hydrates (1/3 and 2/3 water monolayers) provided information concerning the structure and dynamics of the interlayer region that could not be obtained through traditional simulation analysis methods. Cs(+ )formed inner sphere complexes with the mineral surface, and could be seen to jump from one attracting location near a layer charge site to the next, while water molecules were observed to migrate from the hydration shell of one ion to that of another. Neighboring ions maintained a partial hydration shell by sharing water molecules, such that a single water molecule hydrated two ions simultaneously for hundreds of picoseconds. Cs-montmorillonite hydrates featured the largest extent of this sharing interaction, because interlayer ions were able to inhabit positions near surface cavities as well as at their edges, close to oxygen triads. The greater positional freedom of Cs(+ )within the montmorillonite interlayer, a result of structural hydroxyl orientation and low tetrahedral charge, promoted the optimization of distances between cations and water molecules required for water sharing. Preference of Cs(+ )for locations near oxygen triads was observed within interlayer beidellite and hectorite. Water molecules also could be seen to interact directly with the mineral surface, entering its surface cavities to approach attracting charge sites and structural hydroxyls. With increasing water content, water molecules exhibited increased frequency and duration of both cavity habitation and water sharing interactions. Competition between Cs(+ )and water molecules for surface sites was evident. These important cooperative and competitive features of interlayer molecular behavior were uniquely revealed by animation of an otherwise highly complex simulation output

The pharmacological regulation of cellular mitophagy

Small molecules are pharmacological tools of considerable value for dissecting complex biological processes and identifying potential therapeutic interventions. Recently, the cellular quality-control process of mitophagy has attracted considerable research interest; however, the limited availability of suitable chemical probes has restricted our understanding of the molecular mechanisms involved. Current approaches to initiate mitophagy include acute dissipation of the mitochondrial membrane potential (ΔΨm) by mitochondrial uncouplers (for example, FCCP/CCCP) and the use of antimycin A and oligomycin to impair respiration. Both approaches impair mitochondrial homeostasis and therefore limit the scope for dissection of subtle, bioenergy-related regulatory phenomena. Recently, novel mitophagy activators acting independently of the respiration collapse have been reported, offering new opportunities to understand the process and potential for therapeutic exploitation. We have summarized the current status of mitophagy modulators and analyzed the available chemical tools, commenting on their advantages, limitations and current applications