Chemical mapping of tire and road wear particles for single particle analysis.

Tire and road wear particles (TRWP), which are comprised of polymer-containing tread with pavement encrustations, are generated from friction between the tire and the road. Similar to environmentally dispersed microplastic particles (MP), the fate of TRWP depends on both the mass concentration as well as individual particle characteristics, such as particle diameter and density. The identification of an individual TRWP in environmental samples has been limited by inherent characteristics of black particles, which interfere with the spectroscopic techniques most often used in MP research. The purpose of this research was to apply suitable analytical techniques, including scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDX) mapping and time-of-flight secondary ion mass spectrometry (ToF-SIMS) mapping, to characterize the specific physical and chemical properties of individual TRWP. Detailed elemental and organic surface maps were generated for numerous samples including bulk tread material, cryogenically milled tire tread particles, and TRWP generated from two separate road simulator methods. Key physical and chemical characteristics of TRWP for single particle identification included (1) elongated/round shape with variable amounts of mineral encrustation, (2) elemental surface characteristics including co-localization of (S + Zn/Na) ± (Si, K, Mg, Ca, and Al), and (3) co-localization of organic surface markers, such as C6H5+ and C7H7+. Comparisons of TRWP with other polymeric (polystyrene) and non-polymeric (carbon black) particle types demonstrated that a combination of physical and chemical markers is necessary to identify TRWP. Addition of a density separation step to the single particle analysis techniques allowed for the determination of average primary TRWP particle size (34 µm by number distribution and 49 µm by volume distribution) and aspect ratio (65% of TRWP with an aspect ratio > 1.5). The use of chemical mapping techniques, such as SEM/EDX and/or ToF-SIMS mapping as demonstrated herein, can support future research efforts that aim to identify complex MP.

A light-up "G-quadruplex nanostring" for label-free and selective detection of miRNA via duplex-specific nuclease mediated tandem rolling circle amplification.

MicroRNA (miRNA) has emerged as a promising genetic marker for cancer diagnosis and therapy because its expression level is closely related to the progression of malignant diseases. Herein, a label-free and selective fluorescence platform was proposed for miRNA based on light-up "G-quadruplex nanostring" via duplex-specific nuclease (DSN) mediated tandem rolling circle amplification (RCA). First, a long DNA generated from upstream RCA was designed with the antisense sequences for miR-21 and downstream RCA primer. Upon recognizing miR-21, the resulting DNA-RNA permitted DSN digestion and triggered downstream two-way RCA, and generation of abundant "G-quadruplex nanostring" binding with ZnPPIX for label-free fluorescent responses. In our strategy, the strong preference of DSN for perfectly matched DNA/RNA ensures its excellent selectivity. The developed method generated wide linear response with LOD of 1.019 fM. Additionally, the miR-21 levels in cell extracts have been evaluated, revealing the utility of this tool for biomedical research and clinical diagnosis.

A new chemiluminescence method for the determination of 8-hydroxyguanine based on l-histidine bound nickel nanoparticles.

A new chemiluminescence aptasensor for sensitive and efficient detection of 8-hydroxyguanine based on the synergistic interaction of Ni NPs@l-histidine@aptamer@MBs has been developed, and it has been applied in the real urine samples of cancer patients.

Label-free and enzyme-free one-step rapid colorimetric detection of DNA methylation based on unmodified gold nanoparticles.

DNA methylation has been identified as one of the important causes of tumorigenesis, so it is important to develop some advanced methods for detecting and quantifying DNA methylation. In this study, a label-free and enzyme-free one-step rapid colorimetric detection of DNA methylation based on unmodified Au nanoparticles(Au NPs)has been proposed. This method can quickly, efficiently, economically and easily colorimetric detect methylated DNA only by the color change of unmodified Au NPs solution without the covalent modification of Au NPs in advance or complicated instruments for implementation with practical limitations or expensive biological enzymes or traditional organic dyes during the reaction. The strategy employed the difference in electrostatic attraction of single-stranded DNA and double-stranded DNA against salt-induced aggregation of Au NPs. The method has a DNA methylated detection limit of 8.47 nM and it is distinctly visible to detect methylated DNA with the naked eye as low as 20 nM. Furthermore, the strategy has an ability to detect methylated DNA in the presence of abundant unmethylated DNA with the detection limit of 0.13% and as low as 1% methylated DNA can be distinguished in heterogeneous samples with the naked eye. Also, the stratagem provides a convenient and rapid platform for methylated DNA detection of human serum samples in one step, which displays a huge potential for clinical diagnosis and treatment of oncological diseases.

Effects of Senegenin against hypoxia/reoxygenation-induced injury in PC12 cells.

OBJECTIVE: To investigate the effect and the potential mechanism of Senegenin (Sen) against injury induced by hypoxia/reoxygenation (H/R) in highly differentiated PC12 cells. METHODS: The cultured PC12 cells were treated with H/R in the presence or absence of Sen (60 µmol/L). Four groups were included in the experiment: control group, H/R group, H/R+Sen group and Sen group. Cell viability of each group and the level of lactate dehydrogenase (LDH) in culture medium were detected for the pharmacological effect of Sen. Hoechst 33258 staining and annexin V/propidium iodide double staining were used to analyze the apoptosis rate. Moreover, mitochondrial membrane potential (△Ψm), reactive oxygen species (ROS) and intracellular free calcium ([Ca(2+)]i) were measured by fluorescent staining and flow cytometry. Cleaved caspase-3 and activity of NADPH oxidase (NOX) were determined by colorimetric protease assay and enzyme linked immunosorbent assay, respectively. RESULTS: Sen significantly elevated cell viability (P<0.05), decreased the leakage of LDH (P<0.05) and apoptosis rate (P<0.05) in H/R-injured PC12 cells. Sen maintained the value of △Ψm (P<0.05) and suppressed the activity of caspase-3 (P<0.05). Moreover, Sen reduced ROS accumulation P<0.05) and [Ca(2+)]i increment (P<0.05) by inhibiting the activity of NOX (P<0.05). CONCLUSION: Sen may exert cytoprotection against H/R injury by decreasing the levels of intracellular ROS and [Ca(2+)]i, thereby suppressing the mitochondrial pathway of cellular apoptosis.

Feasibility of biogas production from anaerobic co-digestion of herbal-extraction residues with swine manure.

The objective of this work was to examine the feasibility of biogas production from the anaerobic co-digestion of herbal-extraction residues with swine manure. Batch and semi-continuous experiments were carried out under mesophilic anaerobic conditions. Batch experiments revealed that the highest specific biogas yield was 294 mL CH(4) g(-1) volatile solids added, obtained at 50% of herbal-extraction residues and 3.50 g volatile solids g(-1) mixed liquor suspended solids. Specific methane yield from swine manure alone was 207 mL CH(4) g(-1) volatile solid added d(-1) at 3.50 g volatile solids g(-1) mixed liquor suspended solids. Furthermore, specific methane yields were 162, 180 and 220 mL CH(4) g (-1) volatile solids added d(-1) for the reactors co-digesting mixtures with 10%, 25% and 50% herbal-extraction residues, respectively. These results suggested that biogas production could be enhanced efficiently by the anaerobic co-digestion of herbal-extraction residues with swine manure.

Universal method for the fabrication of detachable ultrathin films of several transition metal oxides.

Ultrathin films are important nanoscale structures that are used extensively in a variety of technological contexts. However, it has traditionally been difficult and costly to fabricate detachable and purely inorganic high aspect ratio films with controlled thickness and good uniformity. Here we report a versatile method to make separable purely inorganic membranes of various metal oxides such as Nb(2)O(5), TiO(2), WO(3), and Ta(2)O(5) with thicknesses ranging from 30 to 150 nm. Fluoride ions are migrated through the oxide film and upon arrival at the oxide-metal interface form a sacrificial soluble oxyfluoride layer. Fluorine also plays a role in controlling the porosity of the films. The study exposes the mechanism behind the detachment process that is largely due to the fast migration of fluoride anions relative to oxygen anions. The resulting films have a wide range of potential applications as catalysts or catalyst supports, filtration membranes, sensors, and more.

Gas phase formation of dense alkanethiol layers on GaAs(110).

We present a study of the growth and thermal stability of hexanethiol (C6) films on GaAs(110) by direct recoil spectroscopy with time-of-flight analysis. We compare our results with the better known case of C6 adsorption on Au(111). In contrast to the two-step adsorption kinetics observed for Au surfaces after lengthy exposures, data for C6 adsorption on the GaAs(110) surface are consistent with the formation of a single dense phase of C6 molecules at lower exposures. On the contrary, in solution preparation, dense phases can only be obtained on GaAs for long alkanethiols and after lengthy immersions. The C6 layer has a first desorption peak at 325 K, where partial desorption of the alkanethiol molecules takes place. Fits to the desorption curves result in a 1 eV adsorption energy, in agreement with a chemisorption process. Increasing the temperature to 500 K results in the S-C bond scission with only S remaining on the GaAs(110) surface. The possibility of forming dense, short-alkanethiol layers on semiconductor surfaces from the vapor phase could have a strong impact for a wide range of self-assembled monolayer applications, with only minimal care not to surpass room temperature once the layer has been formed in order to avoid molecular desorption.

In situ extraction of intracellular L-asparaginase using thermoseparating aqueous two-phase systems.

The feasibility and generic applicability of directly integrating conventional discrete operations of cell disruption by high pressure homogenizer and the product capture by aqueous two-phase extraction (ATPE) system have been demonstrated for the extraction of intracellular L-asparaginase from E. coli. In a side-by-side comparison with the conventional ATPE process, including cell disruption, centrifugal clarification and following ATPE, purification of L-asparaginase via this novel in situ ATPE process yielded a product of L-asparaginase with a higher specific activity of 94.8 U/(mg protein) and a higher yield of 73.3%, both of which in the conventional ATPE process were 78.6 U/(mg protein) and 52.1%, respectively. In the purification of L-asparaginase (pI=4.9), product-debris interactions commonly diminish its recovery. It was demonstrated that immediate extraction of L-asparaginase in ATPE systems when it is released at pH 5.0 during cell disruption effectively increased its recovery in the top phase due to the reduced interaction between L-asparaginase and cell debris and the reduced degradation by contaminated protease. In addition, no clarification step and/or disruptate storage are required in this in situ ATPE, which reduced the number of unit operations and thus shortened the overall process time. This novel process has a good potential for the separation of other intracellular biological products.

Self-assembled monolayers of aromatic thiols stabilized by parallel-displaced pi-pi stacking interactions.

Parallel-displaced pi-pi stacking interactions have been known to be the dominant force in stabilizing the double helical structure of DNA and the tertiary structure of proteins. However, little is known about their roles in self-assembled monolayers of other large pi molecules such as aromatic thiols. Here we report on a systematic study of the self-assembled monolayers of four kinds of anthracene-based thiols, 9-mercaptoanthracene (MA), (4-mercaptophenyl) (9-anthryl) acetylene (MPAA), (4-mercaptophenyl) (10-nitro-9-anthryl) acetylene (MPNAA), and (4-mercaptophenyl) (10-carboxyl-9-anthryl) acetylene (MPCAA) on Au(111), in which a spacer and different functional groups (NO2 and COOH) are intentionally designed to introduce and thus allow the investigation of various intermolecular interactions, in addition to pi-pi interactions in the base molecules. We find that all molecules form long-range-ordered monolayers and, more interestingly, that these assembled monolayers exhibit essentially the same fundamental packing structure. On the basis of high-resolution scanning tunneling microscopy observations, we propose the space-filling models for the observed superstructures and demonstrate that all superstructures can be understood in terms of the parallel-displaced pi-pi stacking interactions, despite the presence of competing dipole-dipole and H-bonding interactions associated with these specially designed functional groups.

Improving alachlor biodegradability by ferrate oxidation.

Alachlor can be recalcitrant when present at high concentrations in wastewater. Ferrate oxidation was used as a pretreatment to improve its biodegradability and was evaluated by monitoring alachlor elimination and removal of COD(Cr) (chemical oxygen demand determined by potassium dichromate) during the oxidation process up to a value compatible with biological treatment. Ferrate oxidation resulted in elimination of alachlor followed by degradation of its intermediates. High pH suppressed alachlor removal and COD(Cr) removal due to the low redox potential of ferrate ions. Although alachlor can be totally eliminated within 10 min under optimized conditions (alachlor, 40 mg l(-1); ferrate:alachlor molar ratio, 2; and pH 7.0), its complete mineralization cannot be achieved by ferrate oxidation alone. Alachlor solution treated by ferrate for 10 min inhibited an up-flow biotreatment with activated sludge. The biodegradability of ferrate-pretreated solution improved when the treatment was increased to 20 min, at the point of which BOD(5)/COD(Cr) ratio of the treated solution was increased to 0.87 from 0.35 after 10 min treatment. Under optimized conditions, ferrate oxidation for 20 min resulted in total elimination of alachlor, partial removal of COD(Cr) and the ferrate-treated solution could be effectively treated by the up-flow activated sludge process.