Biofabrication of gold nanoparticles and its biocompatibility in human breast adenocarcinoma cells (MCF-7)

In this paper, a simple and environmentally friendly method for synthesis of gold nanoparticles (AuNPs) using culture supernatant of Bacillus flexus as reductants and stabilizers is reported. The prepared AuNPs were characterized by various analytical techniques. UV–visible spectroscopy, X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) results confirmed that Au³⁺ ions reduced into Au⁰. Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) measurements confirmed that the chemical surface structure of AuNPs. TEM images showed the size and morphology of AuNPs. Moreover, the toxicity studies suggested that AuNPs were neither toxic nor inhibitory to human breast cancer cells (MCF-7).     

In situ wet-cell TEM observation of gold nanoparticle motion in an aqueous solution

In situ wet-cell transmission electron microscopy (TEM) technology enables direct observation of nanomaterials in a fully hydrated environment with high spatial and temporal resolution, which can be used to address a wide range of scientific problems. In this paper, the motions of approximately 5-nm sized gold nanoparticles in an aqueous solution are studied using the wet-cell TEM technology. It is observed that gold nanoparticles can be either in a single particle or cluster forms, and dynamic displacement and rotation motions are observed for both forms in the solution. Under electron beam irradiation, nanoparticles in some clusters gradually fused together; sometimes they also showed dramatic growth behavior. Mechanisms for the motion and growth of the particles/clusters are discussed.     

The Effect of the acetone extract of Arctotis arctotoides (Asteraceae) on the growth and ultrastructure of some opportunistic fungi associated with HIV/AIDS

In this study, the effect of the acetone extract of Arctotis arctotoides (L.f.) O. Hoffm. (Asteraceae) on the growth and ultrastructure of some opportunistic fungi associated with HIV/AIDS was analyzed by means of scanning electron microscope (SEM). Remarkable morphological alterations in the fungal mycelia which were attributed to the loss of cell wall strength ranged from loss of turgidity and uniformity, collapse of entire hyphae to evident destruction of the hyphae. The elements responsible for giving the fungi their characteristic virulence were detected and quantified by energy dispersive X-ray microanalysis techniques. X-ray microanalysis showed the specific spectra of sodium, potassium and sulfur as the principal intersection of the four pathogenic fungi studied. Since these ions have the potential of fostering fungal invasion by altering the permeability of hosts' membranes, their presence was considered inherent to the pathogenicity of the opportunistic fungi. Hence, these findings indicate the potential of the crude extract of A. arctotoides in preventing fungal invasion and subsequent infection of host's membranes.     

High temperature in-situ observations of multi-segmented metal nanowires encapsulated within carbon nanotubes by in-situ filling technique

Multi-segmented one-dimensional metal nanowires were encapsulated within carbon nanotubes (CNTs) through in-situ filling technique during plasma-enhanced chemical vapor deposition process. Transmission electron microscopy (TEM) and environmental TEM were employed to characterize the as-prepared sample at room temperature and high temperature. The selected area electron diffractions revealed that the Pd₄Si nanowire and face-centered-cubic Co nanowire on top of the Pd nanowire were encapsulated within the bottom and tip parts of the multiwall CNT, respectively. Although the strain-induced deformation of graphite walls was observed, the solid-state phases of Pd₄Si and Co-Pd remain even at above their expected melting temperatures and up to 1,550 ± 50°C. Finally, the encapsulated metals were melted and flowed out from the tip of the CNT after 2 h at the same temperature due to the increase of internal pressure of the CNT.     

In situ transmission FTIR spectroelectrochemistry: A new technique for studying lithium batteries

In situ transmission FTIR spectra are measured during the electrochemical insertion of lithium into phospho-olivine FePO₄. The spectroelectrochemical cell consists of a composite FePO₄ cathode, a lithium metal anode, and an electrolyte of 1 M LiPF₆ in a 1:1 mixture of ethylene carbonate and diethyl carbonate (EC-DEC). Bands belonging to the electrolyte and cathode are identified in the infrared spectra of the in situ cells. The antisymmetric PO₄³⁻ bending vibrations (ν₄) are used to monitor Li⁺ insertion into FePO₄. Discharging produces spectral changes that are consistent with the formation of phospho-olivine LiFePO₄, yet the electrolyte bands are not affected by the discharging process. The in situ infrared experiments confirm the two-phase mechanism for lithium insertion into FePO₄. Moreover, the experiments demonstrate the ability to collect in situ transmission FTIR spectra of functioning electrode materials in lithium batteries. Unfortunately, lithium plating occurs on the optical window when the Li//FePO₄ half-cells are charged. The use of an intercalation anode such as graphite could alleviate this problem; however, this avenue of research is not explored in this study.     

Risk-association of CYP11A1 polymorphisms and breast cancer among han chinese women in southern china

Exposure to endogenous sex hormones has been reported as a risk factor for breast cancer. The CYP11A1 gene encodes the key enzyme that catalyzes the initial and rate-limiting step in steroid hormone synthesis. In this study, the associations between single nucleotide polymorphisms (SNPs) in CYP11A1 and breast cancer susceptibility were examined. Six SNPs in CYP11A1 were genotyped using the MassARRAY IPLEX platform in 530 breast cancer patients and 546 healthy controls. Association analyses based on a χ(2) test and binary logistic regression were performed to determine the odds ratio (OR) and 95% confidence interval (95% CI) for each SNP. Two loci (rs2959008 and rs2279357) showed evidence of associations with breast cancer risk. The variant genotype C/T-C/C of rs2959008 was significantly associated with a decreased risk (age-adjusted OR, 0.75; 95% CI, 0.58-0.96; P = 0.023) compared with the wild-type TT. However, the homozygous TT variant of rs2279357 exhibited increased susceptibility to breast cancer (age-adjusted OR, 1.44; 95% CI, 1.05-1.98; P = 0.022). The locus rs2959003 also showed an appreciable effect, but no associations were observed for three other SNPs. Our results suggest that polymorphisms of CYP11A1 are related to breast cancer susceptibility in Han Chinese women of South China.     

A comparative study of two different approaches for the incorporation of silver nanoparticles into layer-by-layer films

In this work, a comparative study about the incorporation of silver nanoparticles (AgNPs) into thin films is presented using two alternative methods, the in situ synthesis process and the layer-by-layer embedding deposition technique. The influence of several parameters such as color of the films, thickness evolution, thermal post-treatment, or distribution of the AgNPs along the coatings has been studied. Thermal post-treatment was used to induce the formation of hydrogel-like AgNPs-loaded thin films. Cross-sectional transmission electron microscopy micrographs, atomic force microscopy images, and UV-vis spectra reveal significant differences in the size and distribution of the AgNPs into the films as well as the maximal absorbance and wavelength position of the localized surface plasmon resonance absorption bands before and after thermal post-treatment. This work contributes for a better understanding of these two approaches for the incorporation of AgNPs into thin films using wet chemistry.     

Aluminum nanopowders produced by electrical explosion of wires and passivated by non-inert coatings: Characterisation and reactivity with air and water

Results of the comprehensive characterisation of electro-exploded aluminum nanopowders, passivated with the non-inert reagents: oleic acid (C₁₇H₃₃COOH) and stearic acid (C₁₇H₃₅COOH), which were suspended in kerosene and ethanol, amorphous boron, nickel, fluoropolymer and Al₂O₃ (for a comparison), are discussed. Aluminum nanopowders with a protecting surface show increased stability towards oxidation in air and in water during the storage period. On the basis of the experimental results, a diagram of the formation and stabilization of the coatings is proposed.     

Review of kinetic models for supercritical fluid extraction

The supercritical fluid extraction (SFE) of liquids and solid materials is gaining increasing interest and commercial application in last decades, most particularly under the recent concept of green chemistry and biorefinery. Hence, it is fundamental to provide adequate modeling of the SFE, in order to optimize operating conditions and simulate the global process. This work intends to review the most significant and physically sound models published in the literature for countercurrent liquid-supercritical fluid extraction and SFE of solid matrices, such as the linear driving force, shrinking core, broken and intact cells, and the combination of BIC and shrinking core models. The main assumptions and mass transfer expressions are presented and discussed.     

Polyacrylonitrile-based nanofibers—A state-of-the-art review

Polyacrylonitrile (PAN), a well-known polymer with good stability and mechanical properties, has been widely used in producing carbon nanofibers (CNFs) as these have attracted much recent attention due to their excellent characteristics, such as spinnability, environmentally benign nature and commercial viability. Among the various precursors to produce CNFs, PAN has been extensively studied due to its high carbon yield and flexibility for tailoring the structure of the final CNFs as well as the ease of obtaining stabilized products due to the formation of a ladder structure via nitrile polymerization. In view of this, they have applications in areas such as electronics, tissue engineering, membrane filtration and high performance composites. This review presents various combinations of PAN and PAN-based precursors in producing CNFs from the PAN homopolymer or its modified precursors, copolymers, blends and various composites. Various modifications of PAN and their future prospects in different scientific and technological disciplines are addressed.     

A review of the features and analyses of the solid electrolyte interphase in Li-ion batteries

The solid electrolyte interphase (SEI) is a protecting layer formed on the negative electrode of Li-ion batteries as a result of electrolyte decomposition, mainly during the first cycle. Battery performance, irreversible charge “loss”, rate capability, cyclability, exfoliation of graphite and safety are highly dependent on the quality of the SEI. Therefore, understanding the actual nature and composition of SEI is of prime interest. If the chemistry of the SEI formation and the manner in which each component affects battery performance are understood, SEI could be tuned to improve battery performance. In this paper key points related to the nature, formation, and features of the SEI formed on carbon negative electrodes are discussed. SEI has been analyzed by various analytical techniques amongst which FTIR and XPS are most widely used. FTIR and XPS data of SEI and its components as published by many research groups are compiled in tables for getting a global picture of what is known about the SEI. This article shall serve as a handy reference as well as a starting point for research related to SEI.     

Complex macromolecular architecture design via cyclodextrin host/guest complexes

The design of complex macromolecular architectures has driven macromolecular engineering over the past decades. The introduction of supramolecular chemistry into polymer chemistry provides novel opportunities for the generation of macromolecular architecture with specific functions. Cyclodextrins are attractive design elements as they form supramolecular inclusion complexes with hydrophobic guest molecules in aqueous solution affording the possibility to combine a large variety of building blocks to form novel macromolecular architectures. In the present critical review, the design of a broad range of macromolecular architectures driven by cyclodextrin host/guest chemistry is discussed, including supramolecular block copolymers, polymer brushes, star and branched polymers.     

Effect of process water chemistry and particulate mineralogy on model oilsands separation using a warm slurry extraction process simulation

Variability in ore composition and process parameters is known to affect bitumen recovery from natural oilsands. In this work, we extend our earlier investigations with model oilsands systems (MOS) to determine the effects of calcium, magnesium and bicarbonate ion concentrations in the process water and their interactions with ‘active’ solids such as: kaolinite, montmorillonite and ultra-fine silica. Our results demonstrate that solids mineralogy and decreasing particle size produce negative outcomes on bitumen recovery related to concomitant effects on bitumen droplet size during flotation. In some cases, certain process water chemistries were found to restore recovery, but clay concentration was the key factor.Naturally acidic oilsands are known to give poor bitumen recoveries. An MOS prepared with connate water at pH 2 responded in the same way. Comparison with a typical oilsands showed no significant differences in middlings pH and the large, negative effect on bitumen recovery was not reversed by higher caustic loading during separation. This result may be caused by irreversible co-flocculation of bitumen and mineral particles during preparation of the MOS and may reflect similar behavior in comparable natural samples.     

Atom transfer radical polymerization (ATRP): A versatile and forceful tool for functional membranes

The progress in atom transfer radical polymerization (ATRP) provides an effective means for the design and preparation of functional membranes. Polymeric membranes with different macromolecular architectures applied in fuel cells, including block and graft copolymers are conveniently prepared via ATRP. Moreover, ATRP has also been widely used to introduce functionality onto the membrane surface to enhance its use in specific applications, such as antifouling, stimuli-responsive, adsorption function and pervaporation. In this review, the recent design and synthesis of advanced functional membranes via the ATRP technique are discussed in detail and their especial advantages are highlighted by selected examples extract the principles for preparation or modification of membranes using the ATRP methodology.     

Ultrasonic and fermented pretreatment technology for diosgenin production from Diosorea zingiberensis C.H. Wright

The present study evaluated the efficiency of ultrasonic and fermented pretreatment technology for diosgenin production from Diosorea zingiberensis C.H. Wright (DZW). The optimum extraction conditions were as follows: ultrasonic pretreatment condition, 20 min, 50 kHz, 100 W; fermented pretreatment condition, 30 °C, 3 d and 0.8 g yeast dosages per 100 g raw materials; acidic hydrolysis condition, 1.5 mol/L sulfuric acid, 4 h; petrol extraction condition, 5 h. Under these conditions, diosgenin yield could reach 2.30%. Scanning electron micrographs indicated morphology changes of materials during diosgenin extraction process. UV-vis and GC-MS analysis revealed wastewater from the new approach contained 20 kinds of organic compounds which were mainly acids, esters, ketones and hydrocarbons. The research indicated the new approach could not only increase 42.5% diosgenin yield, recover 81.6% starch and 50.8% cellulose, but also efficiently reduce 69.7% COD, comparing with the conventional approach.     

Polymer vectors via controlled/living radical polymerization for gene delivery

The design of efficient gene delivery vectors is a challenging task in gene therapy. Recent progress in living/controlled radical polymerizations (LRPs), in particular atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization providing a means for the design and synthesis of new polymeric gene vectors with well-defined compositions, architectures and functionalities is reviewed here. Polymeric gene vectors with different architectures, including homopolymers, block copolymers, graft copolymers, and star-shaped polymers, are conveniently prepared via ATRP and RAFT polymerization. The corresponding synthesis strategies are described in detail. The recent research activities indicate that ATRP and RAFT polymerization have become essential tools for the design and synthesis of advanced, noble and novel gene carriers.     

Conjugated-polymer grafting on inorganic and organic substrates: A new trend in organic electronic materials

This review highlights recent developments in the grafting of conjugated polymers onto various substrates for organic electronic devices. The rapid development of multi-layer architectures demands the preparation of well-defined interfaces between both compatible and incompatible materials. It is promising therefore that interface-engineering is now known to help passivate charge trap states, control energy level alignments, enhance charge extraction, guide active-layer morphologies, and improve material compatibility, adhesion and device stability. In organic electronic devices, conjugated polymers are in contact with a wide range of constituents, such as metals, metal oxides, organic materials, and inorganic particles. Covalent bonds between these materials and macromolecules are desired to yield intimate contacts and well-defined interfaces. Following an overview of the various synthetic methodologies of conjugated polymers, the chemistry of tethering macromolecular chains onto nanoparticles and flat surfaces is described. The creation of functional hybrid materials offers the potential to deliver efficient and low-cost devices.     

When emulsification meets self-assembly: The role of emulsification in directing block copolymer assembly

Emulsification is used to generate spherical particles or droplets of immiscible liquids, while block copolymer self-assembly yields a wide variety of nanostructures. The combination of these two methodologies can yield a variety of structures that would not be otherwise observed. The emulsification/solvent evaporation process provides a powerful means to direct block copolymer assembly. Various factors arising from the emulsification can direct the block copolymer assembly, such as confinement effects, interfacial tension, as well as other conditions. In this review, various emulsification techniques are discussed, such as oil-in-water emulsions, double emulsions, as well as the use of microfluidic devices. While emulsification-induced self-assembly may be used to control internal morphologies as well as overall shapes of particles, it also lends a convenient method for controlling surface structures. Examples of exotic structures that may be obtained through the use of these techniques will be described. Also, ways in which morphologies may be controlled using these methods will be discussed.