A Eu-MOF-Based Fluorescent Sensing Probe for the Detection of Tryptophan and Cu2+ in Aqueous Solutions.

Abnormal tryptophan (Trp) metabolism can be used as an important indicator of chronic hepatitis, paranoia, Parkinson's disease and other diseases. Deficiency or excessive accumulation of Cu2+ can cause diseases such as Wilson's disease and Alzheimer's disease. Eu-based metal-organic framework (Eu-MOF) was successfully prepared for fluorescence sensing of Trp and Cu2+ in an aqueous solution (pH = 7.4). Eu-MOF showed high selectivity and sensitivity for Trp and Cu2+ with detection limits of 0.22 µM and 0.09 µM and Ksv of 6.17 × 103 M- 1 and 2.37 × 104 M- 1 respectively. Trp and Cu2+ had overlapped UV absorption spectra with that of Eu-MOF and competed for the excitation light source. Trp also attenuated the antennae effect of organic ligands on Eu-MOF, thus quenching the red fluorescence of Eu-MOF. This study provides insights into the application of MOFs in bioanalysis and diagnostics.

Velvet-like carbon nitride as a solid-phase microextraction fiber coating for determination of polycyclic aromatic hydrocarbons by gas chromatography.

In this study, velvet-like carbon nitride (V-g-C3N4) was prepared from urea aqueous solutions by one-step thermal polycondensation. The V-g-C3N4 material was then characterized using a scanning electron microscope (SEM), X-ray diffractometer (XRD), Fourier transform infrared spectrophotometer (FT-IR), and nitrogen adsorption-desorption isotherms. The specific surface area of V-g-C3N4 (60.66 m2/g) was 1.8 times that of the carbon nitride (g-C3N4) prepared by the traditional method. V-g-C3N4 was modified on the surface of stainless-steel wire by a sol-gel technique to obtain a solid-phase microextraction (SPME) coating for the extraction of five polycyclic aromatic hydrocarbons (PAHs) from water samples. The chromatography signal of the PAHs extracted using the V-g-C3N4 coating was 1.5 times that when using a g-C3N4 coating, and 5-10 times that when using commercial PDMS. Under the optimized extraction conditions, the linear range of the method developed for the determination of five PAHs was 0.05-100 µg/L, the limits of detection were 0.005-0.012 µg/L, and the recoveries from actual water samples were 85.94-103.47%. Furthermore, the developed SPME device is remarkably durable and can be reused up to 160 times.

Transformation of Thioacids into Carboxylic Acids via a Visible-Light-Promoted Atomic Substitution Process.

A visible-light-promoted atomic substitution reaction for transforming thiocacids into carboxylic acids with dimethyl sulfoxide (DMSO) as the oxygen source has been developed, affording various alkyl and aryl carboxylic acids in over 90% yields. The atomic substitution process proceeds smoothly through the photochemical reactivity of the formed hydrogen-bonding adduct between thioacids and DMSO. A DMSO-involved proton-coupled electron transfer (PCET) and the simultaneous generation of thiyl and hydroxyl radicals are proposed to be key steps for realizing the transformation.

A molecular beacon-like Ag nanocluster fluorescence probe for nucleic acid detection.

We have developed a type of low-cost, label-free silver nanocluster molecular beacon-like fluorescence sensor with a DNA template. To detect target DNA with this probe, we use a hairpin DNA sequence based on a "turn-on" strategy. The transformation of hairpin DNA would visibly influence the formation of Ag nanoclusters, such that the stronger fluorescence will be measured with the solution containing target nucleic acids than that without targets nucleic acids. There is a good liner relationship between the fluorescence and the target DNA concentrations, ranging from 1 to 750 nmol L-1. Importantly, the detection sensing platform allows down to 1 nmol L-1, which is much lower than other studies.

Coating layered double hydroxides with carbon dots for highly efficient removal of multiple dyes.

Layered double hydroxides (LDHs) and layered double oxides (LDOs) are desirable adsorption materials for printing and wastewater treatment owing to their outstanding anion exchange abilities, abundant active sites, and eco-friendly nature. In this study, a versatile LDO hybrid coated with carbon dots (CDs@MgAl-LDO) was constructed by modifying sodium dodecylbenzene sulfonate on the surface of MgAl-LDH as a carbon precursor, followed by ligand carbonization and hydrotalcite dehydration at 450 °C under N2 flow. CDs@MgAl-LDO displayed a hexagonal lamellar architecture with a plate lateral size of approximately 500 nm. It had a higher BET specific surface area (28.61 m2/g) than MgAl-LDO (11.48 m2/g). X-ray diffraction analysis revealed that CDs@MgAl-LDO maintained the "memory effect" of LDOs and could retrieve the original structure when dispersed in water. Moreover, the modified carbon dots change the intrinsically hydrophilic nature of LDOs and help to improve the affinity for organic contaminants, including both cationic and anionic dyes. The adsorption of dyes on CDs@MgAl-LDO followed a pseudo-second-order kinetic model with correlation coefficients (R2) ranging from 0.9901 to 0.9911 and exhibited Freundlich-type heterogeneous adsorption. It showed superior adsorption performance for three dyes, with the maximum adsorption capacity of 3628.9-5174.1 mg/g, thereby outperforming previously reported LDH-based adsorbents. This work developed a facile approach for preparing new carbon dots-LDH hybrids for the highly efficient removal of multiple dyes.

Synthesis of 3D magnetic porous carbon derived from a metal-organic framework for the extraction of clenbuterol and ractopamine from mutton samples.

3D magnetic porous carbon (MPCK) was prepared using the metal-organic framework (MOF) MIL-100(Fe) as the carbon precursor by carbonisation and KOH activation strategies. Carbonisation and activation ensured that MPCK possessed excellent structural and thermal stability, strong magnetic responsiveness and high surface area. MPCK was used as an adsorbent for the magnetic solid-phase extraction of clenbuterol and ractopamine from mutton samples. The concentration levels of analytes were determined by ultra-high performance liquid chromatography-mass spectrometry. Under optimised extraction conditions, the peak area responded linearly to analytes over the concentration range from 0.05 µg L-1 to 40 µg L-1 (r ≥ 0.9972). The detection limits of clenbuterol and ractopamine were found to be 0.130 µg kg-1 and 0.150 µg kg-1, respectively. The satisfactory recoveries in mutton samples ranging from 95.64% to 114.65% indicated that 3D porous carbon is a promising adsorption material for the extraction of clenbuterol and ractopamine from complex biological matrixes.

[Analysis of fatty acids in rice by pseudotargeted metabolomics method based on gas chromatography-mass spectrometry].

A pseudotargeted metabolomics method based on gas chromatography-mass spectrometry (GC-MS) was developed for the analysis of fatty acids in rice. A total of 16 fatty acids were detected in rice. The method was used to identify the difference between fatty acid profiles in rice. The total intensity of the saturated and unsaturated fatty acids was used as the evaluation index. The effects of six extraction methods and four extraction solvents on the extraction efficiencies of the fatty acids were compared. The developed method was used to investigate the fatty acid profiles in five types of rice (Daohuaxiang, Jixing, Jinlangzi, Nongda, and Zhuangyuan). The fatty acid profile in Daohuaxiang rice was different from that in the other four species. The fatty acids in Jinlangzi and Nongda rice were markedly different, while those in Jixing and Jinlangzi rice were similar. The method is simple, stable and accurate, and it can provide basic data for the improvement of rice quality and nutritional value.

Histone H2A-peptide-hybrided upconversion mesoporous silica nanoparticles for bortezomib/p53 delivery and apoptosis induction.

The design and development of advanced gene/drug codelivery nanocarrier with good biocompatibility for cancer gene therapy is desirable. Herein, we reported a gene delivery nanoplatform to synergized bortezomib (BTZ) for cancer treatment with histone H2A-hybrided, upconversion luminescence (UCL)-guided mesoporous silica nanoparticles [UCNPs(BTZ)@mSiO2-H2A]. The functionalization of H2A on the surface of UCNPs(BTZ)@mSiO2 nanoparticles realized the improvement of biocompatibility and enhancement of gene encapsulation and transfection efficiency. More importantly, then UCNPs(BTZ)@mSiO2-H2A/p53 induced specific and efficient apoptotic cell death in p53-null cancer cells and restored the functional activity of tumor suppressor p53 by the success of co-delivery of BTZ/p53. Moreover, the transfection with UCNPs(BTZ)@mSiO2-H2A/p53 in p53-deficient non-small cell lung cancer cells changed the status of p53 and substantially enhanced the p53-mediated sensitivity of encapsulated BTZ inside the UCNPs(BTZ)@mSiO2/p53. Meanwhile, core-shell structured mesoporous silica nanoparticles UCNPs@mSiO2 as an UCL agent can detect the real-time interaction of nanoparticles with cells and uptake/penetration processes. The results here suggested that the as-developed UCNPs(BTZ)@mSiO2-H2A/p53 nanoplatform with coordinating biocompatibility, UCL image, and sustained release manner might be desirable gene/drug codelivery nanocarrier for clinical cancer therapy.

Dispersive solid-phase extraction of bisphenols migrated from plastic food packaging materials with cetyltrimethylammonium bromide-intercalated zinc oxide.

The migration of bisphenols (BPs) can take place from plastic packaging materials into freshly cooked takeaway food, especially at high temperatures. In this study, cetyltrimethylammonium bromide-intercalated zinc oxide (ZnO@CTAB) was developed and used to extract the migration of BPs (bisphenol A and bisphenol AF) from disposable plastic materials to contained food simulates. Several experimental parameters that influence extraction efficiency were investigated. Under optimal conditions, a sensitive dispersive solid-phase extraction method based on ZnO@CTAB was proposed for the analysis of BPs coupled with ultra-high performance liquid chromatography and time-of-flight mass spectrometry. The method exhibited good linearity of calibration, high recovery (97.63-109.33%), low limits of detection 0.027-0.030 µg L-1, and acceptable precisions. The developed method was used to carry out a migration test from two disposable plastic bags and a disposable plastic container, using distilled water at 100 °C as a hot liquid food simulant. The migration concentrations of bisphenol AF was found to be 0.42 µg L-1 and 0.86 µg L-1 for the two types of disposable plastic bags, and the concentration of bisphenol A was 0.49 µg L-1 for disposable plastic container. The proposed method was also applied to investigate the migration of BPAF from the disposable plastic bags to different food simulants, revealing that the release of BPAF levels depended on the polarity of the liquid food components.

Design and Synthesis of Ag Nanocluster Molecular Beacon for Adenosine Triphosphate Detection.

This study presents a fluorescence method for detecting adenosine triphosphate (ATP) based on a label-free Ag nanocluster molecular beacon (MB) with high sensitivity. The sensor contains a hairpin-shaped MB, two short single-stranded DNA strands, and T4 DNA ligase. The MB consists of three parts, which are the template DNA sequence for synthesizing Ag nanoclusters at the 5' end, the middle DNA with a hairpin-shaped structure, and the guanine base-rich DNA sequence at the 3' end. The sensor exhibits high fluorescence intensity in the absence of ATP. However, when the probe is used for ATP detection, the two short DNA sequences in the sensor would form a long sequence by enzymatic ligation reaction; this long sequence opens the hairpin-shaped structure of the MB and decreases the fluorescence of the system. Under optimal analytical conditions, a clear linear relationship is observed between ATP concentration and fluorescence intensity in the range of 0.1-10 µM. The interference presented by other small molecules during ATP detection is evaluated, and results confirm the good selectivity of the proposed sensor. Compared with traditional methods, the sensor is label free, easy to operate, inexpensive, and highly sensitive.

Fabrication of glucose-derived carbon-decorated magnetic microspheres for extraction of bisphenols from water and tea drinks.

Glucose-derived carbon-decorated magnetic microspheres were synthesized by an easy hydrothermal carbonization method and used as a high-efficiency adsorbent to extract bisphenols in water and tea drinks. The as-prepared carbon-decorated magnetic microspheres had a well-defined core-shell structure with a shell thickness of about 5 nm. The microspheres possessed high saturation magnetization at 60.8 emu/g and excellent chemical stability in aqueous solution. The experimental parameters affecting the extraction efficiency, including extraction time, pH, adsorbent dosage, desorption solvents, desorption time, and solution volume were evaluated. Electrostatic and π-π interactions were the major driving forces during extraction. Overall, a new magnetic solid-phase extraction method of determining bisphenols was developed on the basis of as-prepared magnetic microspheres. The method had a wide linear range, low limits of detection (0.03-0.10 µg/L), and high recoveries (85.4-104.6%).

Metabolic responses of Saccharomyces cerevisiae to ethanol stress using gas chromatography-mass spectrometry.

Ethanol, as one of the most important biological fuels, is mainly produced by Saccharomyces cerevisiae. But with the accumulation of ethanol, the viability and growth of Saccharomyces cerevisiae is often stressed during fermentation. At present, the reaction mechanism of Saccharomyces cerevisiae to ethanol stress has not been fully elucidated. In this paper, a metabolomics approach with gas chromatography-mass spectrometry was performed to investigate the metabolic changes of Saccharomyces cerevisiae cultured with 0%, 2% and 5% ethanol. The results of partial least-squares discriminant analysis (PLS-DA) clearly reflected the metabolic variations induced by ethanol stress. It was found that in total 36 metabolites changed significantly with univariate analysis, including amino acids, organic acids, and fatty acids. The citrate cycle and alanine, aspartate and glutamate metabolism were found as the markedly perturbed metabolic pathways. Significant alterations of metabolites in these pathways (succinic acid, citric acid, pyruvate, fumarate, glutamate, aspartate, alanine) indicated that ethanol stress impeded the citrate cycle at the node of citrate. This might cause insufficient energy supply of the cell and the synthesis reduction of some amino acids and other substrates. Furthermore, the growth of the cell was slowed down. These results demonstrated that metabolomics has potential to reveal the regulation mechanisms for ethanol stress in Saccharomyces cerevisiae.

Recyclable magnetic NiFe2O4/C yolk-shell nanospheres with excellent visible-light-Fenton degradation performance of tetracycline hydrochloride.

A photo-Fenton-like reaction was considered as an effective method for wastewater treatment because it could produce more oxidative species such as hydroxyl radicals (˙OH) to accelerate the reaction. In this paper, a NiFe2O4/C (abbr. as NFO/C) yolk-shell nanostructure was synthesized via one-step calcination using polyacrylic acid sodium salt (PAAS) NPs as a template. The nanocomposite was characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption-desorption, among others. The magnetically separable nanocomposite exhibited a high activity and recyclability towards the photodegradation of tetracycline hydrochloride (TC). In addition, the factors affecting the photodegradation process were systematically investigated, including the dosage of the NiFe2O4/C catalyst, the pH of the solution, and the volume of H2O2. Notably, the degradation rate of tetracycline hydrochloride (TC) reached 97.25% in 60 min in the presence of H2O2 under visible light irradiation (λ > 400 nm) with NiFe2O4/C. This work provides a simple and novel method to construct NiFe2O4/C yolk-shell nanostructures, which may be applied to the photodegradation of tetracycline hydrochloride from wastewater. Finally, a photocatalytic and stability mechanism is proposed, which may help us more comprehensively understand the photo-Fenton mechanism.

Fe-doped H3PMo12O40 immobilized on covalent organic frameworks (Fe/PMA@COFs): a heterogeneous catalyst for the epoxidation of cyclooctene with H2O2.

Covalent organic frameworks (COFs) have arisen as one kind of devisable porous organic polymer that has attracted immense attention in catalytic applications. In this work, we prepared cost-effective imine-based COFs (COF-300, COF-LZU1 and CIN-1) via a reaction kettle operated in place of a traditional sealed Pyrex tube. Then, phosphomolybdic acid (PMA) and iron ions were immobilized on the COF supports by impregnation; the resulting frameworks were denoted as Fe/PMA@COFs (Fe/PMA@COF-LZU1, Fe/PMA@CIN-1 and Fe/PMA@COF-300). A series of characterization results demonstrated that the PMA and iron ions were uniformly dispersed on the surface/cavities of the COFs. The catalytic properties of the obtained Fe/PMA@COFs were investigated in the epoxidation of cyclooctene with H2O2 as the oxidant. The experimental results show that the Fe/PMA@CIN-1 composite can act as an efficient heterogeneous catalyst for the epoxidation of cyclooctene. The intramolecular charge transfer between the COFs and the dual sites (PMA and Fe ions), the spatial structure and the nitrogen content of the COFs played critical roles in dispersing and stabilizing the active species, which are closely connected with the activity and stability of the catalysts. A novel efficient heterogeneous catalyst for the epoxidation of olefins via a simple and cost-effective process is provided, and this experiment demonstrates the notable application prospects of the covalent organic skeleton as a catalyst support.

Ultrasensitive Biosensor for Detection of Mercury(II) Ions Based on DNA-Cu Nanoclusters and Exonuclease III-assisted Signal Amplification.

This paper describes a novel method for label-free mercury(II) ion detection based on exonuclease III-induced target signal recycling amplification using double-stranded DNA templated copper nanoclusters. The synthesized DNA-Cu nanoclusters were used with exonuclease III loop amplification technology for ultra-high sensitivity detection of mercury(II) ions, which were detected by significantly decreased fluorescence intensity. Under the optimal experimental conditions, there was a clear linear relationship between Hg2+ concentration in the range of 0.04 to 8 nM and fluorescence intensity. The detection limit for Hg2+ was 4 pM. In addition, the interference of other metal ions on the mercury(II) ion detection was also studied. To confirm the application of the fluorescent sensor, it was applied to determine the concentrations of mercury(II) ions in tap water, and the results showed that the method can be used to detect mercury(II) ions in water samples successfully.

Magnetic solid-phase extraction of fluoroquinolones from water samples using titanium-based metal-organic framework functionalized magnetic microspheres.

In this study, a unique core-shell titanium-based metal-organic framework (MOF) functionalized magnetic microsphere was constructed and utilized as magnetic adsorbent for enrichment of five fluoroquinolones from water samples. The received magnetic MOF nanocomposite, denoted as Fe3O4@Cys@MIL125-NH2, showed strong magnetic responsiveness, and good hydrophilicity, as well as excellent affinity to the target analytes. Under optimal conditions, the developed magnetic solid-phase extraction (MSPE) method, combined with ultra-high performance liquid chromatography (UPLC), showed good linearity within the studied concentration range, and low limits of detection (0.05-0.2 µg L-1). The accuracy of the developed method was evaluated by measuring the extraction recovery of the spiked tap water and river water samples. The satisfactory recoveries of five fluoroquinolones were in the range of 83.8-109.4% with the RSDs lower than 8.9%. These results indicated that the as-prepared Fe3O4-Cys@MIL125-NH2 is a promising magnetic adsorbent for efficient enrichment of fluoroquinolones from tap water and environmental water samples.

Synergistic apoptotic effects of silibinin in enhancing paclitaxel toxicity in human gastric cancer cell lines.

Gastric cancer (GC) is the 3rd leading cause of tumor­associated mortality worldwide. The efficacy of paclitaxel, a frequently used GC chemotherapeutic agent, is hindered due to drug resistance, dose­induced toxicity and adverse side effects. Silibinin, an active compound of a widely consumed dietary supplement, milk thistle extract, has recently been demonstrated to have strong antitumor efficacy in a human GC cell model. Thus, to enhance the efficacy of GC treatment, the present study evaluated whether silibinin exerted a synergistic therapeutic effect with paclitaxel. It was observed that the combination of silibinin­paclitaxel was able to trigger cell cycle arrest and apoptosis. The cell cycle arrest assay indicated that silibinin and paclitaxel alone induced a G2/M phase arrest, and the silibinin­paclitaxel combination strongly inhibited G2/M cells from entering the S phase. The apoptosis assay and western blot analysis of poly­ADP­ribose polymerase, pro­caspase 3 and pro­caspase 8 demonstrated that silibinin synergized with paclitaxel in promoting SGC­7901 GC cell apoptosis. Furthermore, upregulation of the ratio of apoptosis regulator Bcl­2/apoptosis regulator BAX and tumor necrosis factor receptor superfamily member 6 (Fas)/Fas ligand indicated that the silibinin­paclitaxel combination activated the death receptor­mediated pathway in SGC­7901 cells. The results of the present study suggested that silibinin enhanced the therapeutic potential of paclitaxel against human GC SGC­7901 cells.

Magnetic solid-phase extraction of tetracyclines using ferrous oxide coated magnetic silica microspheres from water samples.

A novel magnetic solid-phase extraction approach was proposed for extraction of potential residues of tetracyclines (TCs) in tap and river water samples, based on Fe3O4@SiO2@FeO magnetic nanocomposite. Characterized results showed that the received Fe3O4@SiO2@FeO had distinguished magnetism and core-shell structure. Modified FeO nanoparticles with an ∼5 nm size distribution were homogeneously dispersed on the surface of the silica shell. Owing to the strong surface affinity of Fe (II) toward TCs, the magnetic nanocomposite could be applied to efficiently extract three TCs antibiotics, namely, oxytetracycline, tetracycline and chlortetracycline from water samples. Several factors, such as sorbent amount, pH condition, adsorption and desorption time, desorption solvent, selectivity and sample volume, influencing the extraction performance of TCs were investigated and optimized. The developed method showed excellent linearity (R > 0.9992) in the range of 0.133-333 µg L-1, under optimized conditions. The limits of detection were between 0.027 and 0.107 µg L-1 for oxytetracycline, tetracycline and chlortetracycline, respectively. The feasibility of this method was evaluated by analysis of tap and river water samples. The recoveries at the spiked concentration levels ranged from 91.0% to 104.6% with favorable reproducibility (RSD < 4%).

Analysis of microcystins using high-performance liquid chromatography and magnetic solid-phase extraction with silica-coated magnetite with cetylpyridinium chloride.

Microcystins (MCs), produced by freshwater cyanobacteria, can be serious water pollutants, so it is important to monitor their concentration in drinking water. We have developed a method for rapid and accurate determination of microcystin levels in environmental water, using magnetic solid-phase extraction and high-performance liquid chromatography with UV detection. The magnetic composite material, which was combined with cetylpyridinium chloride, was prepared by hydrothermal synthesis. The optimal extraction of microcystins in water sample was achieved by optimizing the amount of adsorbent, time of adsorption, ratio of eluting solvent, and volume of eluent. Under the optimal conditions, the limit of detection of MC-LR was 0.001 µg/L, and the limit of quantification was 0.0028 µg/L. The limit of detection of MC-RR was 0.001 µg/L, and the limit of quantification was 0.003 µg/L. These values are far lower than those established by the International Health Organization for the maximum concentration of microcystins in drinking water. The magnetic solid-phase extraction adsorbent used in this method has the advantages of simple preparation, low price, and easy solid-liquid separation, and it can be used for the rapid and sensitive monitoring of trace microcystins in environmental water samples.

A fluorescence-quenching method for quantitative analysis of Ponceau 4R in beverage.

CdTe quantum dots was synthesized and used to quantitative analysis of Ponceau 4R in solution. With the excitation wavelength of 380nm the emission of CdTe quantum dots was quenched obviously by Ponceau 4R. In order to detect Ponceau 4R in mild condition the influences of fluorescence emission wavelength of CdTe quantum dots, pH value, temperature and reaction time were examined to establish the experimental condition. The linear response of the fluorescence intensity of CdTe quantum dots to Ponceau 4R allowed the quantitative analysis of Ponceau 4R in a range of 2.5-25µg/mL, and the limit of detection for Ponceau 4R was 0.025µg/mL. In addition, the responsive mechanism of this reaction system was investigated in detail by using the modified Stern-Volmer equation and thermodynamic calculation. Particularly, this method was used to quantitatively analyze the real sample, which indicated that this method could be more widely applied in similar samples.