Development of a NiFe2O4 covalent organic framework based magnetic solid-phase extraction approach for specific capture of quinolones in animal innards prior to UHPLC-Q-Orbitrap HRMS detection.

This study aimed to present a selective and effective method for analyzing quinolones (QNs) in food matrix. Herein, a NiFe2O4-based magnetic sodium disulfonate covalent organic framework (NiFe2O4/COF) was prepared using a simple solvent-free grinding method, and was adopted as a selective adsorbent for magnetic solid phase extraction of QNs. Coupled with UHPLC-Q-Orbitrap HRMS, an efficient method for simultaneous detection of 18 kinds of QNs was established. The method exhibited good linearity (0.01-100 ng g-1), high sensitivity (LODs ranging from 0.0011 to 0.0652 ng g-1) and precision (RSDs below 9.5%). Successful extraction of QNs from liver and kidney samples was achieved with satisfactory recoveries ranging from 82.2% to 108.4%. The abundant sulfonate functional groups on NiFe2O4/COF facilitated strong affinity to QNs through electrostatic and hydrogen bonding interactions. The proposed method provides a new idea for the extraction of contaminants with target selectivity.

Enhancing the water-resistance of MOF-199 film through incorporation of microporous organic networks for solid-phase microextraction of BTEX in aqueous environments with improved efficiency.

BACKGROUND: The practical application of moisture sensitive metal organic frameworks (MOFs) in extraction technology faces challenges related to competitive adsorption and water stability. The target analytes cannot be effectively extracted under humid conditions due to the competitive moisture adsorption and/or framework structure collapse of MOFs. In this study, the microporous organic networks (MONs) were synthesized through Sonogashira coupling reaction to use for hydrophobic modification on the surface of MOF-199. RESULTS: The MOF-199@MON as coating was deposited on stainless steel wires for solid-phase microextraction (SPME) of benzene series (BTEX) in aqueous environments. Under the optimal extraction conditions, the MOF-199@MON coated fiber for SPME coupled with GC-MS for the determination of BTEX gave the linear range of 0.5-500 µg L-1, the limit of detections (LODs, S/N = 3) of 0.01-0.04 µg L-1, the limit of quantifications (LOQs, S/N = 10) of 0.04-0.12 µg L-1, the enhancement factors of 3567-4878, and the intra-day, inter-day and fiber-to-fiber precisions (relative standard deviations, RSDs) of 1.0-9.8, 1.9-7.9 and 4.5-9.5 %, respectively. The developed method was successfully applied to the analysis of BTEX in water samples with the recoveries of 71.0 %-113 %. SIGNIFICANCE: This work reveals the home-made SPME fibers have a long service life (the extraction efficiency of fiber decreased by only 7.26 %-13.14 % after 100 cycles). The potential of MON functionalized MOFs as effective adsorbents for the SPME of pollutants in the water environment.

RASFF1A inhibits the epithelial-mesenchymal transition of lens epithelial cells induced by TGFß through regulating HDAC6.

To explore the role of Ras-association domain family 1 A (RASSF1A) in TGFß2-induced changes of lens epithelial cells (LECs) behavior. The human LEC line SRA01/04 cells were treated with TGFß2 in the presence or absence of RASSF1A and histone deacetylase 6 (HDAC6). qRT-PCR and western blot were performed to analysis mRNA and proteins expression. Cell proliferation was evaluated using MTT assay and colony formation assay. Transwell and scratch-wound healing assays were conducted to detected cell migration ability. RASSF1A was downregulated in TGFß2-induced SRA01/04 cells. RASSF1A overexpression inhibited the cell viability, colony formation and migration abilities of SRA01/04 cells induced by TGFß2. Overexpression of RASSF1A suppressed TGFß2-induced EMT of SRA01/04 cells, which was manifested as inhibition of EMT-related proteins α-SMA, Vimentin, Snail and Fn expression. Moreover, RASSF1A down-regulated the expression of HDAC6. Importantly, HDAC6 reversed the effects of RASSF1A on SRA01/04 cells. These findings indicate that RASSF1A prevented TGFß2-induced proliferation, migration, and EMT of LECs by regulating HDAC6 expression, suggesting that RASSF1A holds promise as a potential target for cataracts treatment.

Two-Dimensional Nitrogen-Doped Carbon Nanosheets Derived from g-C3N4 /ZIF-8 for Solid-Phase Microextraction in Exhalation of Esophageal Cancer Patients.

Here, two-dimensional (2D) nitrogen-doped carbon nanosheets (CNSs) were prepared through carbonizing MOFs (ZIF-8) in-situ grown using graphitic carbon nitride (g-C3N4) as a template. The developed ZIF-8 CNS was then used as solid-phase microextraction (SPME) fiber coating for beneficiation of five biomarkers in exhalation of patients with esophageal cancer and in gas chromatography-mass spectrometry (GC-MS) for determination. The ZIF-8 CNS fiber exhibits satisfactory enrichment factors (3490-5631), wide linearity (5-1000 µg L-1), and low detection limits (0.26-0.96 µg L-1). The relative standard deviations (RSDs) for six replicate extractions of the same ZIF-8 CNS fiber were between 2.0-3.9% (intra-day) and 2.8-5.2% (inter-day). The reproducibility of three fibers prepared by the same approach was in the range 6.8-12.3% (RSD). The developed ZIF-8 CNS fiber can persist in 120 SPME cycles with no prominent loss of extraction efficiency and precision. The high enrichment factors of the 2D ZIF-8 CNS coatings are attributed to the high specific surface area, ultrathin thickness, and nano-pore or interlayer channels; moreover, nitrogen doping also endows the π system with a strong electron absorption ability, which will enhance the π-π interaction between the ZIF-8 CNS and the aromatic ring. Ultimately, the self-made ZIF-8 CNS-coated SPME fiber was applied to the analysis of exhaled breath samples. The recoveries of spiked analytes are between 84 and 105%.

In situ encapsulation of SQDs by zinc ion-induced ZIF-8 growth strategy for fluorescent and colorimetric dual-signal detection of alkaline phosphatase.

Controllable encapsulation of sulfur quantum dots (SQDs) into metal-organic frameworks (ZIF-8) by a surface-bound zinc ion-induced growth strategy, and SQDs@ZIF-8 was successfully prepared for alkaline phosphatase (ALP) detection. The new synthesis procedure involves first binding Zn2+ to the surface of SQDs to form SQDs/Zn, and then via zinc ion-induced in situ ZIF-8 growth to obtain SQDs@ZIF-8, which greatly improved the luminous efficiency of SQDs. The specific process of detecting ALP using pH-triggered fluorescence quenching of SQDs@ZIF-8: firstly ALP hydrolyzes 2-phosphate-l-ascorbic acid trisodium salt (AAP) to ascorbic acid (AA), and then the leakage of SQDs in the SQDs@ZIF-8 leads to a decrease in fluorescence intensity based on the destruction of ZIF-8 skeleton by H+ released by AA. A linear relationship was obtained between the fluorescence intensity and the ALP concentration in the range of 0.15-50 U/L, and the detection limit was 0.044 U/L. Moreover, it was found that free SQDs can be complexed with Fe2+ to produce wine red complexes, and the obtained UV absorbance and ALP concentration have a linear relationship in the range of 10-200 U/L. The detection range of ALP is significantly broadened based on the combination of the above two detection methods. Furthermore, SQDs@ZIF-8 exhibited excellent stability in water and was successfully applied to the fluorescence and colorimetric detection of ALP in human serum.

Distributed Localization for Multi-Agent Systems With Random Noise Based on Iterative Learning.

This article is concerned with the real-time localization problem for the dynamic multi-agent systems with measurement and communication noises under directed graphs. The barycentric coordinates are introduced to describe the relative position between agents. A novel robust distributed localization estimation algorithm based on iterative learning is proposed. The relative-distance unbiased estimator constructed from the historical iterative information is used to suppress the measurement noise. The designed stochastic approximation method with two iterative-varying gains is used to inhibit the communication noise. Under the zero-mean and independent distributed conditions on the measurement and communication noises, the asymptotic convergence of the proposed methods is derived. The numerical simulation and the QBot-2e robot experiment are conducted to test and verify the effectiveness and the practicability of the proposed methods.

Highly Selective Detection of Paraoxon in Food Based on the Platform of Cu Nanocluster/MnO2 Nanosheets.

Selective and sensitive identification of paraoxon residue in agricultural products is greatly significant for food safety but remains a challenging task. Herein, a detection platform was developed by integrating Cu nanoclusters (Cu NCs) with MnO2 nanosheets, where the fluorescence of Cu NCs was effectively quenched. Upon introducing butyrylcholinesterase and butyrylcholine into the system, their hydrolysate, thiocholine, leads to the decomposition of the platform through a reaction between the MnO2 nanosheets and thiol groups on thiocholine. The electron-rich groups on thiocholine can further promote the fluorescence intensity of Cu NCs through host-guest interactions. Adding paraoxon results in the failure of fluorescence recovery and further promotion, which could be utilized for the quantitative detection of paraoxon, and a limit of detection as low as 0.22 ng/mL can be achieved. The detection platform shows strong tolerance to common interference species, which endows its applications for the detection of paraoxon in vegetables and fruit. These presented results not only open a new door for the functionalization of metal nanoclusters but also offer an inspiring strategy for analytic techniques in nanomedicine and environmental science.

Recent Advances in the Application and Mechanism of Carbon Dots/Metal-Organic Frameworks Hybrids in Photocatalysis and the Detection of Environmental Pollutants.

Metal-organic frameworks (MOFs) are a class of crystalline porous materials with simple synthesis conditions, large specific surface area, structural diversity, and a wide range of interesting properties. The integration of MOFs with other materials can provide new multifunctional composites that exhibit both component properties and new characteristics. In recent years, the integration of carbon dots (CDs) into MOFs to form composites has shown improved optical properties and fascinating new characteristics. This review focuses on the design and synthesis strategies of CDs@MOFs composites (including pore-confined synthesis, in situ encapsulation, post-synthesis modification and impregnation method) and their recent research progress in photocatalysis and detection of environmental pollutants. Both the achievements and problems are evaluated and proposed, and the opportunities and challenges of CDs@MOF composite are discussed.

A novel thiolysis-high-performance liquid chromatography method for the determination of proanthocyanidins in grape seeds.

A novel thiolysis-high-performance liquid chromatography method for the quantitative determination of total proanthocyanidins and the mean degree of polymerization in grape seeds has been developed. Following thiolysis with formic acid and benzyl mercaptan, reaction products were separated and purified. Three proanthocyanidin monomers and three derivatives were obtained and their structures were identified by liquid chromatography-mass spectrometry, FTIR spectroscopy, and NMR spectroscopy. A decomposition model of the thiolysis products and a correction formula for proanthocyanidins concentration were established. This thiolysis-high-performance liquid chromatography method displayed good calibration linearity (R2  > 0.999 over the concentration range 0.01 to 10 mg/mL), excellent accuracy (recoveries of 97.9-99.6%), and precision (repeatability relative standard deviations of 0.45-0.75%). This method is suitable for the quantitative analysis of proanthocyanidins in grape seed products.

Design and construction strategies to improve covalent organic frameworks photocatalyst's performance for degradation of organic pollutants.

Covalent organic frameworks (COFs) are a class of crystalline porous organic polymers. In recent years, COFs have received extensive attention in the field of photocatalytic degradation due to their large specific surface area, good thermal and solvent stability, and diverse structures. This review studies the progress of COF in the field of photocatalytic degradation, and summarizes the strategies to improve the photocatalytic activity of covalent organic frameworks, including the designs of ligands and structures. In particular, the design and construction of the COF composites (COF/MOF, COF/g-C3N4, COF/metal semiconductor) are discussed. The photocatalytic mechanism is described in detail, and the prospect of COFs in photocatalytic degradation is prospected.

Glutathione modulated fluorescence quenching of sulfur quantum dots by Cu2O nanoparticles for sensitive assay.

Sulfur quantum dots (S-dots) show great potential for applications in various field, due to their favorable biocompatibility, high stability, and antibacterial properties. However, the use of S-dots in chemical sensing is limited by the lack of functional groups on the surface. In this work, a fluorescence glutathione (GSH) assay is developed based on the GSH modulated quenching effect of Cu2O nanoparticles (NP) on S-dots. The fluorescence of S-dots is effectively quenched after forming complex with Cu2O NP through a static quenching effect (SQE). Introducing of GSH can trigger the decomposition of Cu2O NP into GSH-Cu(I) complex, which leads to the weaken of SQE and the partial recover of the fluorescence. The intensity of recovered fluorescence shows a positive correlation with the concentration of GSH in the concentration range of 20 to 500 µM. The fluorescence GSH assay shows excellent selectivity and robustness towards various interferences and high concentration salt, which endow the successful detection of GSH in human blood sample. The presented results provide a new door for the design of fluorescence assays, which also provides a platform for the applications in nanomedicine and environmental science.

Recent advances in porous organic frameworks for sample pretreatment of pesticide and veterinary drug residues: a review.

Rapid and accurate detection of pesticide and veterinary drug residues is a continuing challenge because of the complex matrix effects. Thus, appropriate sample pretreatment is a crucial step for the effective extraction of the analytes and removal of the interferences. Recently, the development of nanomaterial adsorbents has greatly promoted the innovation of food sample pretreatment approaches. Porous organic frameworks (POFs), including polymers of intrinsic microporosity, covalent organic frameworks, hyper crosslinked polymers, conjugated microporous polymers, and porous aromatic frameworks, have been widely utilized due to their tailorable skeletons and pores as well as fascinating features. This review summarizes the recent advances for POFs to be utilized in adsorption and sample preparation of pesticide and veterinary drug residues. In addition, future prospects and challenges are discussed, hoping to offer a reference for further study on POFs in sample pretreatment.

Hollow zeolitic imidazolate framework-7 coated stainless steel fiber for solid phase microextraction of volatile biomarkers in headspace gas of breast cancer cell lines.

In this work, we reported the preparation of the hollow zeolitic imidazolate framework-7 (ZIF-7) via etching ZIF-7 with tannic acid, and further fabricated the hollow ZIF-7 coated fiber for the solid phase microextraction (SPME) of the five volatile biomarkers (acetone, isopropanol, hexanal, hexanol and decanal) generated from breast cancer cell lines. The hollow structure not only endowed higher extraction performance for the SPME of analytes, but also improved the diffusion rate of the analytes inside the hollow ZIF-7. Under the optimal conditions, the hollow ZIF-7 coated fiber offered high extraction capacity (25-153 mg g-1) and enhancement factors (EFs, 2023-11250) for the five biomarkers, good linearity (R2 > 0.9918) of acetone and isopropanol (2.5-500 µg L-1) and hexanol, hexanal, and decanal (1.0-100 µg L-1), low limits of detection (S/N = 3) of 0.07-0.53 µg L-1 and the limit of quantifications (LOQs, S/N = 10) of 0.23-1.76 µg L-1. The precisions (RSDs, %) for intra-day (n = 6), inter-day (n = 5) and fiber-to-fiber (n = 6) were 2.8-7.5%, 4.3-8.5%, and 4.2-14.6%, respectively. The high EFs of the hollow ZIF-7 coated fiber for the five biomarkers resulted from the integrated effects of the large surface area, the unique porous structure, hydrophobic interaction, gate-opening effect, and enhanced properties after etching including faster mass transport, multiple active components, and more exposed active sites. The fabricated hollow ZIF-7 coated fiber lasted at least 140 cycles of extraction/desorption/aging without obvious decrease of extraction ability and no change of crystal structure. Finally, the hollow ZIF-7 coated fiber combined with GC-FID had been successfully used to detect the five biomarkers in the headspace gas of human breast cancer cell lines (MDA-MB-231) and normal mammary cell lines (CCD-1095Sk) with the recoveries of 84-105%. These results revealed the prospect of hollow MOFs as efficient adsorbents for sample pretreatment.

Hybrid ZIF-8-90 for Selective Solid-Phase Microextraction of Exhaled Breath from Gastric Cancer Patients.

Metal-organic frameworks (MOFs) are a new kind of microporous materials whose unique properties make them promising as coatings for solid phase microextraction (SPME). However, previous MOF coatings for SPME exclusively focus on single-linker MOFs, and the selective enrichment of polar or nonpolar targets depends on the polarity of linker on the surface of MOFs, which greatly limits the application of MOF coating for SPME in real samples. Here, we report a hybrid MOF-coated stainless steel fiber for SPME of biomarkers in exhaled breath from gastric cancer patients. Zeolitic imidazolate framework-8-90 (ZIF-8-90) possesses the aldehyde groups and methyl groups in the framework as a model MOF, and eight biomarkers (ethanol, acetone, hexanal, hexanol, nonane, isoprene, heptane, and decane) were used as the target analytes. The ZIF-8-90-coated fiber shows high enrichment efficiency for hydrophilic targets and hydrophobic targets, wide linearity (three orders of magnitude), and low detection limits (0.82-2.64 µg L-1). The ZIF-8-90-coated fiber exhibited higher enrichment performance for all the investigated analytes as a result of the synergy of methyl and aldehyde groups, the porous structure, and the suitable pore size of ZIF-8-90 (4-5 Å). The relative standard deviation (RSD) of six repetitions for extractions using the same ZIF-8-90-coated fiber ranged from 2.5 to 7.3%. The reproducibility between the three fibers prepared in parallel varied in the range of 4.8-12% (RSD). The fabricated ZIF-8-90-coated fiber lasted for at least 120 cycles of extraction/desorption/conditioning without an obvious reduction in extraction efficiency and precision. Finally, the developed ZIF-8-90-coated SPME fiber has been successfully used for the analysis of exhaled breath samples from gastric patients with satisfied recoveries (88-106%).

Electrochemical biosensors based on antibody, nucleic acid and enzyme functionalized graphene for the detection of disease-related biomolecules.

The unique physical structure and chemical and electrical properties of graphene make it an ideal choice for sensor materials. The sensing platform of biomolecule functionalized graphene has received extensive attention due to its high sensitivity and selectivity, especially the biosensors constructed by combining antibodies, nucleic acids and enzymes that efficiently recognize specific targets with graphene having a large specific surface area and a fast electron transfer rate, which has become a significant research direction. In this paper, electrochemical biosensors based on graphene materials developed in recent years are summarized. The methods of functional modification of graphene, graphene oxide and reduced graphene oxide with antibodies, nucleic acids and enzymes are briefly described. In addition, the advantages and disadvantages of the constructed electrochemical biosensors in detecting pathogens and disease markers are also reviewed. Finally, we are optimistic about this prospect for the development direction and application prospects of such electrochemical biosensors.

Selective extraction and detection of ß-agonists in swine urine for monitoring illegal use in livestock breeding.

The illegal use of ß-agonists often endangers animal-derived food safety. In this study, a selective detection method for ß-agonists in swine urine was established via the combination of polymeric ionic liquid-molecularly imprinted graphene oxide-miniaturized pipette tip solid-phase extraction and high-performance liquid chromatography. It is worth noting that this method relied mainly on the designed adsorbent, which presented a rich adsorption mechanism, fast mass transfer rate, and high selectivity, and was successfully utilized in the selective extraction of ß-agonists from swine urine samples. The proposed method has low LOD (0.20-0.56 ng/mL), high recovery (94.9-107.9%), and high reusability (4 times, 91.9-108.8%), which indicates its high potential as a selective, sensitive, accurate, and nonfatal method for monitoring the illegal use of ß-agonists in the livestock breeding stage.

Functionalized metal-organic frameworks for photocatalytic degradation of organic pollutants in environment.

Currently, many kinds of organic pollutants in air and water have a negative impact on humans and the environment. Notably, as a type of new functional materials, metal-organic frameworks (MOFs) with well-ordered porous structures and numerous active sites have been proven to be ideal photocatalysts for the degradation of organic pollutants. In the past few years, many encouraging achievements have been made in the research field of MOFs for photocatalysis. And a large number of functionalized MOFs have been constructed to improve photocatalytic activity. In this review, recent progress in the photocatalytic degradation of organic pollutants in both air and water using functionalized MOFs are summarized in detail. The focus is on photocatalytic mechanisms and some strategies employed to achieve higher degradation efficiency. Furthermore, the challenges and outlooks in this promising filed are also discussed. We hope this review would be useful for designing more functionalized MOFs with greater photocatalytic performance for the degradation of organic pollutants in the environment.

Metal-organic frameworks for the sorption of acetone and isopropanol in exhaled breath of diabetics prior to quantitation by gas chromatography.

A method is described for non-invasive glucose monitoring of diabetics by means of breath analysis. The metal-organic frameworks (MOFs) ZIF-7, UiO-66 and MOF-5 were chosen as sorbents in packed tubes for sampling and preconcentration of acetone and isopropanol which are established diabetes biomarkers. The MOF UiO-66 was found to be the most appropriate sorbent. Following thermal desorption, acetone and isopropanol where quantified by GC. The method has low limits of detection (0.79-0.84 µg·L-1) and wide linear ranges (5-2000 µg·L-1). It is assumed that the good performance of UiO-66 as a sorbent results from its large surface area and unique porous structure, and from van der Waals interactions. The relative standard deviation for six replicate cycles of sampling and preconcentration using one 50 mg UiO-66 packed tube ranged between 2.3 and 6.7% for intra-day assays, and from 2.7 to 4.3% for inter-day assays. A tube packed with 50 mg of UiO-66 packed tube can be used in over 120 cycles of adsorption/desorption without significant loss of collection efficiency. The GC method has been applied for the analysis of diabetic breath samples, and the recoveries from spiked samples ranged from 89.1 to 107.6%. Graphical abstract Schematic presentation of metal-organic frameworks as sorbents combined with thermal desorption-gas chromatography for the determination of acetone and isopropanol in exhaled breath of diabetics.

Preparation of restricted-access material precolumns by grafting δ-gluconolactone onto a hybrid silica monolithic column for on-line solid-phase extraction of tetracycline residues from milk.

A restricted-access material-hybrid monolithic column was prepared based on single-component organosiloxane and dynamic grafting of δ-gluconolactone for on-line solid phase extraction of tetracycline antibiotic residues from milk. The hybrid monolithic column was prepared in a stainless-steel chromatographic column using methyltrimethoxysilane as the single precursor. δ-Gluconolactone was covalently coupled to aminopropyl derivatized hybrid monolithic column, which formed hydrophilic structures on the surface of the pore of the restricted-access material-hybrid monolithic column. The columns were characterized by scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, nitrogen adsorption, contact angle analysis, dynamic adsorption, and chromatographic performance evaluation. The restricted-access material-hybrid monolithic column was applied to the on-line extraction of tetracycline residues from milk. An enrichment factor of 15.8 and a good sample clean-up effect were obtained under the optimized conditions. The recoveries of the three spiked milk samples were between 81.7 and 102.5% with relative standard deviations (n = 3) in the range of 2-5%. The limits of detection (S/N = 3) for target compounds were in the range of 3.80-9.03 µg/kg. The results show that the on-line extraction using the restricted-access material-hybrid monolithic column was powerful for food sample pretreatment with high selectivity and good clean-up effect.

Luminescent switch sensors for the detection of biomolecules based on metal-organic frameworks.

Metal-organic frameworks (MOFs) as sensing materials have experienced explosive growth in recent years due to their intrinsic merits, such as structural diversity, high porosity, large surface area, extraordinary adsorption affinities, etc. Biomolecules such as DNA, protein, and vitamins play vital roles in metabolism. Moreover, the sensitive detection of biomolecules is of importance in the disease prevention and treatment. This review intends to provide an update on the recent progress in the detection of various biomolecules via MOF-based luminescent sensors. MOFs are successful in the detection of DNA, RNA, protein, and other biomolecules. MOF-based luminescent sensors function by utilizing different mechanisms, including luminescent responses of enhancement and quenching, which are defined as "turn-on" and "turn-off" responses, respectively. Then, a short comparison of the "turn-on" and "turn-off" types of sensors is also made.