Tuning the planarity of molecularly imprinted covalent organic frameworks for selective extraction of ochratoxin A in alcohol samples

Here, we report a monomer planarity modulation strategy for room-temperature constructing molecularly imprinted-covalent organic frameworks (MI-COFs) for selective extraction of ochratoxin A (OTA). 2,4,6-triformylphloroglucinol (Tp) was used as basic building block, while three amino monomers with different planarity were employed as modulators to explore the effect of planarity on the selectivity of MI-COFs. The MI-TpTapa constructed from Tp and the lowest planarity of monomer Tapa gave the highest selectivity for OTA, and was further used as the adsorbent for dispersed-solid phase extraction (DSPE) of OTA in alcohol samples. Coupling MI-TpTapa based DSPE with high-performance liquid chromatography allowed the matrix-effect free determination of OTA in alcohol samples with the limit of detection of 0.023 μg kg-1 and the recoveries of 91.4-97.6%. The relative standard deviation (RSD, n = 6) of intra and inter day was <3.2%. This work provides a new way to construct MI-COFs for selective extraction of hazardous targets.

Engineering of molecularly imprinted cavity within 3D covalent organic frameworks: An innovation for enhanced extraction and removal of microcystins

The scarcity of selective adsorbents for efficient extraction and removal of microcystins (MCs) from complex samples greatly limits the precise detection and effective control of MCs. Three-dimensional covalent organic frameworks (3D COFs), characterized by their large specific surface areas and highly ordered rigid structure, are promising candidates, but suffer from lack of specific recognition. Herein, we design to engineer molecularly imprinted cavities within 3D COFs via molecularly imprinted technology, creating a novel adsorbent with exceptional selectivity, kinetics and capacity for the efficient extraction and removal of MCs. As proof-of-concept, a new CC bond-containing 3D COF, designated JNU-7, is designed and prepared for copolymerization with methacrylic acid, the pseudo template L-arginine and ethylene dimethacrylate to yield the JNU-7 based molecularly imprinted polymer (JNU-7-MIP). The JNU-7-MIP exhibits a great adsorption capacity (156 mg g-1) for L-arginine. Subsequently, the JNU-7-MIP based solid-phase extraction coupled with high performance liquid chromatography-mass spectrometry achieves low detection limit of 0.008 ng mL-1, wide linear range of 0.025-100 ng mL-1, high enrichment factor of 186, rapid extraction of 10 min, and good recoveries of 92.4%-106.5% for MC-LR. Moreover, the JNU-7-MIP can rapidly remove the MC-LR from 1 mg L-1 to levels (0.26-0.35 μg L-1) lower than the WHO recommended limit for drinking water (1 μg L-1). This work reveals the considerable potential of 3D COF based MIPs as promising adsorbents for the extraction and removal of contaminants in complex real samples.

Size-Dependent Deformation and Competition H-Bond Site-Induced Individual Fluorescence Response of a Single-Crystal Three-Dimensional Covalent Organic Framework

Understanding the individual fluorescence response mechanism of covalent organic frameworks (COFs) at a single-crystal level is of great significance for the rational design of COF-based microsensors but unreachable because all previous COF-based sensors are performed with average fluorescence response behavior of various sized polycrystalline COFs. Herein, we design to explore the fluorescence response of a monodisperse single-crystal COF and further reveal the individual heterogeneity of the response mechanism. Three-dimensional single-crystal COF-301 (SCOF-301) with an intramolecular H-bond-induced excited-state intramolecular proton-transfer effect is selected as a proof-of-concept SCOF. With ethanol, benzene, and ammonia as model analytes, three different deformation and competition H-bond site-induced fluorescence response mechanisms related to crystal size are revealed. Small single particles of SCOF-301 (SSCOF-301) exhibit a more flexible structure, leading to the dominant role of deformation in the fluorescence response of small-sized SSCOF-301. The decreasing flexibility of SSCOF-301 with the increase of crystal size results in involvement of competition of the H-bond site to the fluorescence response besides deformation. Further increase of the crystal size makes the large-sized SSCOF-301 difficult to deform; thus, the competition of the H-bond site dominates the fluorescence response. This work provides a deep understanding of the individual fluorescence response mechanism of COFs to guide the design of a functional COF sensor with suitable size and mechanism for different structural analytes.

Integrating molecular imprinting into flexible covalent organic frameworks for selective recognition and efficient extraction of aflatoxins

Covalent organic frameworks (COFs) are promising adsorbents for extraction, but their selectivity for molecular recognition remains a challenging issue due to the very limited structural design with rigid structure. Herein, we report an elegant strategy for the design and synthesis of molecularly imprinted flexible COFs (MI-FCOFs) via one-pot reaction between the flexible building block of 2,4,6-tris(4-formylphenoxy)- 1,3,5-triazine and linear 4-phenylenediamine for selective extraction of aflatoxins. The flexible chain structure enabled the developed MI-FCOF to adjust the shape and conformation of frameworks to suit the template molecule, giving high selectivity for aflatoxins recognition. Moreover, MI-FCOF with abundant imprinted sites and function groups exhibited an exceptional adsorption capacity of 258.4 mg g-1 for dummy template which is 3 times that of no-imprinted FCOF (NI-FCOF). Coupling MI-FCOF based solid-phase extraction with high-performance liquid chromatography gave low detection limits of 0.003-0.09 ng mL-1 and good precision with relative standard deviations ≤ 6.7% for the determination of aflatoxins. Recoveries for the spiked rice, corn, wheat and peanut samples were in the range of 85.4%- 105.4%. The high selectivity of the developed MI-FCOF allows matrix-free determination of AFTs in food samples. This work offers a new way to the design of MI-FCOF for selective molecular recognition.

Pore Size Adjustment Strategy for the Fabrication of Molecularly Imprinted Covalent Organic Framework Nanospheres at Room Temperature for Selective Extraction of Zearalenone in Cereal Samples

Covalent organic frameworks (COFs) are attractive adsorbents for sample pretreatment due to their unique structure and properties. However, the selectivity of COFs for the extraction of hazardous compounds is still limited due to the lack of specific interactions between COFs and targets. Herein, we report a pore size adjustment strategy for room-temperature synthesis of molecularly imprinted COF (MICOF) for selective extraction of zearalenone (ZEN) in complex food samples. The three-dimensional building block tetra(4-aminophenyl) methane was used as a functional monomer, while dialdehyde monomers with different numbers of benzene ring were used to adjust the pore size of MICOF to match with the size of ZEN molecules. The prepared MICOF gave the largest adsorption capacity of 177.2 mg g-1 and the highest imprinting factor of 10.1 for ZEN so far. MICOF was used as the adsorbent for dispersed solid-phase extraction in combination with high-performance liquid chromatography for the determination of trace ZEN in cereals. The high selectivity of the developed method allows simple aqueous standard calibration for the matrix effect-free determination of ZEN in food samples. The limit of detection and the recoveries of the developed method were 0.21 μg kg-1 and 93.7-101.4%, respectively. The precision for the determination of ZEN was less than 3.8% (RSD, n = 6). The developed method is promising for the selective determination of ZEN in complex matrices.

Pure Covalent-Organic Framework Membrane as a Label-Free Biomimetic Nanochannel for Sensitive and Selective Sensing of Chiral Flavor Substances

Chiral flavor substances play an important role in the human perception of different tastes. Here, we report a pure covalent-organic framework (COF) membrane nanochannel in combination with a chiral gold nanoparticles (AuNPs) selector for sensing chiral flavor substances. The pure COF membrane with a proper pore size is selected as the nanochannel, while l-cysteine-modified AuNPs (l-Cys-AuNPs) are used as the chiral selector. l-Cys-AuNPs show stronger binding to the S-enantiomer than the R-enantiomer, causing current reduction to different degrees for the R- and S-enantiomer to achieve chiral sensing due to the synergistic effect of the size exclusion of the COF nanochannel and the chiral selectivity of l-Cys-AuNPs. The developed COF membrane nanochannel sensing platform not only allows an easy balance of the permeability and selectivity, which is difficult to achieve in traditional polymer membrane nanochannel sensors, but also exhibits better chiral performance than commercial artificial anodic aluminum oxide (AAO) nanochannel sensors. The developed nanochannel sensor is successfully applied for sensing flavor enantiomers such as limonene, propanediol, methylbutyric acid, and butanol with the enantiomer excess values of 55.2% (propanediol) and 72.4% (limonene) and the low detection limits of 36 (limonene) and 71 (propanediol) ng L-1. This study provides a new idea for the construction of nanochannel platforms based on the COF for sensitive and selective chiral sensing.

General Two-Step Method for the Fabrication of Covalent-Organic Framework-Bound Open-Tubular Capillary Columns for High-Resolution Gas Chromatography Separation of Isomers

Covalent organic frameworks (COFs) are promising as stationary phases for gas chromatography (GC). The successful anchoring of COFs to the inner walls of the capillary with good uniformity is an important prerequisite to ensure the excellent separation performance of columns. However, current methods for the fabrication of COF-based capillary columns cannot always meet this requirement when faced with different COFs, which hampers the further development of COF-based GC stationary phases. Here, we show a general two-step method for the fabrication of COF-bound capillary column. The first step enables the formation of uniform amorphous polymer layer on the inner walls of capillary, while the second step allows the facile transformation of the amorphous polymer layer into a highly crystalline COF layer. COF-bound capillary columns with different framework structures were fabricated successfully by the developed two-step method. Impressively, the COF layers bound on the inner walls of these capillary columns showed good uniformity and high crystallinity. More importantly, as an example, the fabricated Tab-DHTA-bound capillary column showed good resolution (R > 1.5) and high column efficiency (700-39,663 plates m-1) for the tested isomers of ethylbenzene, xylene, dichlorobenzene, chlorotoluene, pinene, 1,3-dichloropropene, and propylbenzene with good precision (RSD, run-to-run, n = 5) (retention time, 0.2-0.6%; peak area, 0.5-1.1%; and peak height, 0.5-1.4%). In general, the fabricated Tab-DHTA-bound capillary column exhibited better performance for the separation isomers than commercial columns DB-5 and HP-FFAP. These results indicate that the two-step method is an efficient way to fabricate the COF-bound capillary column with excellent separation performance.

Biomass-derived carbon dots with light conversion and nutrient provisioning capabilities facilitate plant photosynthesis

Carbon dots (CDs)-enabled agriculture has been developing rapidly, but small-scale synthesis and high costs hinder the agricultural application of CDs. Herein, biomass-derived carbon dots (B-CDs) were prepared on a gram-level with low cost, and these B-CDs significantly improved crop photosynthesis. The B-CDs, exhibiting small size and blue fluorescence, were absorbed by crops and enhanced photosynthesis via light-harvesting. Foliar application of B-CDs (10 mg·kg-1) could promote chlorophyll synthesis (30-100 %), Ferredoxin (Fd, 40-80 %), Rubisco enzyme (20-110 %) and upregulated gene expression (20-70 %), resulting in higher net photosynthetic rates (130-300 %), dry biomass (160-300 %) and fresh biomass (80-150 %). Further, the B-CDs could increase crop photosynthesis under nutrient deficient conditions, which was attributed to the release of nutrients from B-CDs. Therefore, the B-CDs enhanced the photosynthesis via enhancing light conversion and nutrient supply. This study provides a promising material capable of enhancing photosynthesis for sustainable agriculture production.

Surface imprinted-covalent organic frameworks for efficient solid-phase extraction of fluoroquinolones in food samples

Molecularly imprinting on covalent organic frameworks (MI-COF) is a promising way to prepare selective adsorbents for effective extraction of fluoroquinolones (FQs). However, the unstable framework structure and complex imprinting process are challenging for the construction of MI-COF. Here, we report a facile surface imprinting approach with dopamine to generate imprinted cavities on the surface of irreversible COF for highly efficient extraction of FQs in food samples. The irreversible-linked COF was fabricated from hexahydroxytriphenylene and tetrafluorophthalonitrile to ensure COF stability. Moreover, the introduction of dopamine surface imprinted polymer into COF provides abundant imprinted sites and endows excellent selectivity for FQs recognition against other antibiotics. Taking enrofloxacin as a template molecule, the prepared MI-COF gave an exceptional adsorption capacity of 581 mg g-1, a 2.2-fold enhancement of adsorption capacity compared with nonimprinted COF. The MI-COF was further explored as adsorbent to develop a novel solid-phase extraction method coupled with high-performance liquid chromatography for the simultaneous determination of enrofloxacin, norfloxacin and ciprofloxacin. The developed method gave the low limits of detection at 0.003-0.05 ng mL-1, high precision with relative standard deviations less than 3.5%. The recoveries of spiked FQs in food samples ranged from 80.4% to 110.7%.

Trifluoromethyl-Functionalized 2D Covalent Organic Framework for High-Resolution Separation of Isomers

Development of novel functional materials for effective isomer separation is of great significance in environmental science, chemical industry, and life science due to the different functions of isomers. However, the similar physicochemical properties of isomers make their separation greatly challenging. Here, we report the fabrication of trifluoromethyl-functionalized 2D covalent organic framework (COF) TpTFMB with 2,2'-bis(trifluoromethyl)benzidine (TFMB) and 1,3,5-triformylphloroglucinol (Tp) for the separation of isomers. TpTFMB was in situ-grown on the inner surface of a capillary for the high-resolution separation of isomers. The introduction of hydroxyl and trifluoromethyl functional groups with uniform distribution in 2D COFs is a powerful tactic to endow TpTFMB with various functions such as hydrogen bonding, dipole interaction, and steric effect. The prepared TpTFMB capillary column enabled the baseline separation of positional isomers such as ethylbenzene and xylene, chlorotoluene, carbon chain isomers such as butylbenzene and ethyl butanoate, and cis-trans isomers 1,3-dichloropropene. The hydrogen-bonding, dipole, and π-π interactions as well as the structure of COF significantly contribute to the isomer separation. This work provides a new strategy for designing functional 2D COFs for the efficient separation of isomers.

Particle Size Regulation of Single-Crystalline Covalent Organic Frameworks for High Performance of Gas Chromatography

Although polycrystalline covalent organic frameworks (PCOFs) have already shown great potential as stationary phases for chromatography, irregular shape and size distribution of PCOFs make regulation of particle size of PCOFs for high separation performance impossible, which is accessible by the application of single-crystalline COFs (SCOFs). Herein, we showed preparation of three-dimensional SCOF (SCOF-303) bonded capillaries (SCOF-303-capillary) with different particle sizes (about 0.4-1.6 μm) and further investigated gas chromatographic separation ability of these SCOF-303-capillaries for isomers of xylene, dichlorobenzene, and pinene. It was found resolution and column efficiency of SCOF-303-capillaries for isomers decreased with the increase in particle size, mainly resulting from the weaker size-exclusion effect and higher mass transfer resistance of the larger particle size of flexible SCOF-303. The obtained SCOF-303-capillary (particle size of ∼0.4 μm) offered baseline separation of xylene isomers with the high resolution of 2.26-3.52, great efficiency of 7879 plates m^-1 for p-xylene, better than PCOF-303-capillary, and commercial DB-5 and HP-FFAP capillary columns as well as many reported capillaries. This work not only shows the great potential of SCOFs for gas chromatography but also provides the theoretical direction for the design of the efficient COF based stationary phase by adjusting the particle sizes.

Irreversible fluorine covalent organic framework based probe nanoelectrospray ionization mass spectrometry for direct and rapid determination of perfluoroalkyl carboxylic acids

Probe nanoelectrospray ionization mass spectrometry (PESI-MS) is practically desirable for rapid and ultra-sensitive analysis of trace contaminants in environment, but limited with the stable and selective probe coating. Herein, we show the design and preparation of irreversible fluorine-based covalent organic framework (TFPPA-F₄) covalently bonded probe to couple with ESI-MS (TFPPA-F₄-PESI-MS) for direct and rapid determination of perfluoroalkyl carboxylic acids (PFCAs) in environmental water. Chemical bonding coating of irreversible crystalline TFPPA-F₄ not only improved stability of the probe, but also offered accessible multiple interactions including hydrophobic, hydrogen bonding and F-F interactions to promote the kinetics and selectivity for PFCAs. The proposed TFPPA-F₄-PESI-MS realized rapid determination of PFCAs (about 4 min) with low limits of detection of 0.06-0.88 ng L^-1 and wide linear range of 1-5000 ng L^-1 (R² of 0.9982-0.9998). Recoveries for the spiked lake and pond water were 85.9-111.1 %. TFPPA-F₄ based probe can maintain the extraction performance after 100 times of extraction. This work shows the great potential of the irreversible covalent organic framework based PESI-MS in rapid and ultra-sensitive determination of contaminants in environmental samples.

Cicada-Wing-Inspired Highly Sensitive Tactile Sensors Based on Elastic Carbon Foam with Nanotextured Surfaces

Electronic devices with tactile and pressure-sensing capabilities are becoming increasingly popular in the automatic industry, human motion/health monitoring, and artificial intelligence applications. Inspired by the natural nanotopography of the cicada wing, we propose here a straightforward strategy to fabricate a highly sensitive tactile sensor through nanotexturing of erected polyaniline (PANI) nanoneedles on a conductive and elastic three-dimensional (3D) carbon skeleton. The robust and compressible carbon networks offer a resilient and conducting matrix to catering complex scenarios; the biomimetic PANI nanoneedles firmly and densely anchored on a 3D carbon skeleton provide intimate electrical contact under subtle deformation. As a result, a piezoresistive tactile sensor with ultrahigh sensitivity (33.52 kPa^-1), fast response/recovery abilities (97/111 ms), and reproducible sensing performance (2500 cycles) is developed, which is capable of distinguishing motions in a wide pressure range from 4.66 Pa to 60 kPa, detecting spatial pressure distribution, and monitoring various gestures in a wireless manner. These excellent performances demonstrate the great potential of nature-inspired tactile sensors for practical human motion monitoring and artificial intelligence applications.

Silicon Nanodots Increase Plant Resistance against Herbivores by Simultaneously Activating Physical and Chemical Defenses

Nanosilicon applications have been shown to increase plant defenses against both abiotic and biotic stresses. Silicon quantum nanodots (Si NDs), a form of nanosilicon, possess excellent biological and physiochemical properties (e.g., minimal size, high water solubility, stability, and biocompatibility), potentially making them more efficient in regulating plant responses to stress than other forms of silicon. However, to date, we still lack mechanistic evidence for how soil-applied Si NDs alter the regulation of plant physical and chemical defenses against insect herbivores. To address this gap, we compared the effect of fluorescent amine-functionalized Si NDs (5 nm) and the conventional fertilizer sodium silicate on maize (Zea mays L.) physical and chemical defenses against the oriental armyworm (Mythimna separata, Walker) caterpillars. We found that 50 mg/kg Si NDs and sodium silicate additions inhibited the growth of caterpillars the most (35.7% and 22.8%, respectively) as compared to other application doses (0, 10, and 150 mg/kg). Both Si NDs and silicate addition activated biosynthesis genes responsible for chemical (benzoxazinoids) and physical (lignin) defense production. Moreover, Si NDs upregulated the gene expression of antioxidant enzymes (SOD, CAT, and POD) and promoted the antioxidant metabolism (flavonoids) in maize leaves under M. separata attack. Finally, we show that, under field conditions, Si ND addition increased maize cob weight (28.7%), cob grain weight (40.8%), and 100-grain weight (26.5%) as compared to the control, and more so than the conventional silicon fertilizer. Altogether, our findings highlight the potential for Si NDs to be used as an effective and ecofriendly crop protection strategy in agroecosystems.

[The role and mechanism of tumor metastasis-associated gene 1 in radiosensitivity of HeLa cells]

Objective: To determine the effect of tumor metastasis-associated gene 1 (MTA1) on the sensitivity of HeLa cells to radiotherapy, and to clarify its molecular mechanism. Methods: The transcriptome differences between MTA1 knocked down Hela cells and control cells were analyzed, and the differentially expressed genes (DEGs) was used to perform Gene-Set Enrichment Analysis (GSEA) and Gene Ontology (GO) cluster analysis. Flow cytometry was used to detect apoptosis in MTA1-overexpressed HeLa cells and control cells before and after 10 Gy X-ray irradiation. Cloning formation assay and real-time cellular analysis (RTCA) were used to monitor the cell proliferation before and after 2 Gy X-ray irradiation. To dissect the underlying molecular mechanisms of MTA1 affecting the sensitivity of radiotherapy, the proteins encoded by the DEGs were selected to construct a protein-protein interaction network, the expression of γ-H2AX was detected by immunofluorescence assay, and the expression levels of γ-H2AX, β-CHK2, PARP and cleaved caspase 3 were measured by western blot. Results: By transcriptome sequencing analysis, we obtained 649 DEGs, of which 402 genes were up-regulated in MTA1 knockdown HeLa cells and 247 genes were down-regulated. GSEA results showed that DEGs associated with MTA1 were significantly enriched in cellular responses to DNA damage repair processes. The results of flow cytometry showed that the apoptosis rate of MTA1 over-expression group (15.67±0.81)% after 10 Gy X-ray irradiation was significantly lower than that of the control group [(40.27±2.73)%, P<0.001]. After 2 Gy X-ray irradiation, the proliferation capacity of HeLa cells overexpressing MTA1 was higher than that of control cells (P=0.024). The numbers of colon in MTA1 over-expression group before and after 2 Gy X-ray irradiation were (176±7) and (137±7) respectively, higher than (134±4) and (75±4) in control HeLa cells (P<0.05). The results of immunofluorescence assay showed that there was no significant expression of γ-H2AX in MTA1 overexpressed and control HeLa cells without X-ray irradiation. Western blot results showed that the expression level of β-CHK2 in MTA1-overexpressing HeLa cells (1.04±0.06) was higher than that in control HeLa cells (0.58±0.25, P=0.036) after 10 Gy X-ray irradiation. The expression levels of γ-H2AX, PARP, and cleaved caspase 3 were 0.52±0.13, 0.52±0.22, and 0.63±0.18, respectively, in HeLa cells overexpressing MTA1, which were lower than 0.87±0.06, 0.78±0.12 and 0.90±0.12 in control cells (P>0.05). Conclusions: This study showed that MTA1 is significantly associated with radiosensitivity in cervical cancer HeLa cells. MTA1 over-expression obviously reduces the sensitivity of cervical cancer cells to X-ray irradiation. Mechanism studies initially indicate that MTA1 reduces the radiosensitivity of cervical cancer cells by inhibiting cleaved caspase 3 to suppress apoptosis and increasing β-CHK2 to promote DNA repair.

Urea-linked covalent organic framework functionalized polytetrafluoroethylene film for selective and rapid thin film microextraction of rhodamine B

Incorporation of highly selective and stable adsorbent with facile extraction technology is desired in practical analysis. Here we show the rational preparation of a urea-linked covalent organic framework functionalized polytetrafluoroethylene film (COF-117-PTFE) with ordered porous structure, rich functional groups, and large surface area-to-volume ratio as the effective adsorbent for convenient, selective and rapid thin film microextraction (TFME) of rhodamine B (RB). The COF-117-PTFE based TFME coupled with high performance liquid chromatography-fluorescence detector (HPLC-FLD) successfully realized the determination of RB with the limit of detection of 0.007 μg L^-1, the linear range of 0.1 - 100 μg L^-1. The relative standard deviation (RSD) of intraday (n = 5) and interday (n = 5) for the determination of 10 μg L^-1 RB were 2.3% and 6.8%, respectively. The absolute recoveries were 80.3%, 71.2% and 67.9% in river water, chili powder and Sichuan pepper powder, respectively. The recoveries for RB spiking in complicated real samples (dry chili, chili powder, dry Sichuan pepper, Sichuan pepper powder and river water) ranged from 90.4% to 107.5%. The developed COF-117-PTFE based TFME-HPLC-FLD method is promising in practical application. This work reveals the high potential of functionalized COF film as the adsorbent for effective extraction of trace contaminants in complicated samples.

Integrating Ordered Two-Dimensional Covalent Organic Frameworks to Solid-State Nanofluidic Channels for Ultrafast and Sensitive Detection of Mercury

Grafting specific recognition moieties onto solid-state nanofluidic channels is a promising way for selective and sensitive sensing of analytes. However, the time-consuming interaction between recognition moieties and analytes is the main hindrance to the application of nanofluidic channel-based sensors in rapid detection. Here, we show the integration of ordered two-dimensional covalent organic frameworks (2D COFs) to solid-state nanofluidic channels to achieve rapid, selective, and sensitive detection of contaminants. As a proof of concept, a thiourea-linked 2D COF (JNU-3) as the recognition unit is covalently bonded on the stable artificial anodic aluminum oxide nanochannels (AAO) to fabricate a JNU-3@AAO-based nanofluidic sensor. The rapid and selective interaction of Hg(II) with the highly ordered channels of JNU-3 allows the JNU-3@AAO-based nanofluidic sensor to realize ultrafast and precise determination of Hg(II) (90 s) with a low limit of detection (3.28 fg mL^-1), wide linear range (0.01-100 pg mL^-1), and good precision (relative standard deviation of 3.8% for 11 replicate determination of 10 pg mL^-1). The developed method was successfully applied to the determination of mercury in a certified reference material A072301c (rice powder), real water, and rice samples with recoveries of 90.4-99.8%. This work reveals the great potential of 2D COFs-modified solid-state nanofluidic channels as a sensor for the rapid and precise detection of contaminants in complicated samples.

Engineering linkage as functional moiety into irreversible thiourea-linked covalent organic framework for ultrafast adsorption of Hg(II)

Development of novel functionalized covalent organic frameworks (COFs) as adsorbent for removal of mercury from environment is of great significance, but the conventional strategies for functionalizing COFs always sacrifice porous properties and suppress the exposure of functional sites, which goes against the rapid adsorption of Hg(II). Here, we show the rational design and preparation of the first thiourea-linked COFs via engineering the COFs linkage as functional moiety for ultrafast and selective adsorption of Hg(II). Two thiourea-linked COFs JNU-3 and JNU-4 were prepared via tautomerism reaction of 1,3,5-triformylphloroglucinol with 1,4-phenylenebis(thiourea) and 1,4-biphenylenebis(thiourea), respectively. The thiourea serves as not only linkage to connect the building block into irreversible crystalline structure, but also functional moiety to give no occupation of the COF pore and full exposure to Hg(II) with strong affinity, offering the JNU-3 and JNU-4 large adsorption capacity (960 and 561 mg g^-1, respectively) and ultrafast kinetics (equilibrium time of 10 s) for Hg(II). The proposed strategy for the design of functional COFs with inherent linkage as functional moiety largely promotes the performance of COFs for diverse applications.

Building-block exchange synthesis of amino-based three-dimensional covalent organic framework for gas chromatographic separation of isomers

The thermally stable three-dimensional covalent organic framework (3D COFs) with rich pore of channels and cages are promising as stationary phase for gas chromatography (GC), which has not been explored....

Aptamer Self-Assembly-Functionalized Nanochannels for Sensitive and Precise Detection of Chloramphenicol

Sensitive and precise determination of chloramphenicol (CAP) is of great significance for human health due to its high risk in trace amounts. Solid-state artificial nanochannels are expected to be highly promising sensing devices owing to single-molecule sensitivity, target-specific selectivity, and portability. Herein, we report an aptamer self-assembly-functionalized artificial nanochannel-based sensor for highly sensitive and precise determination of CAP. Aptamer self-assembly (AAs) served as the specific recognition component and were in situ grown on the surface of stable anodic aluminum oxide (AAO) nanochannels to develop an AAs@AAO nanochannel-based sensor. Selective interaction with CAP led to the disassembly of AAs and sensitive current change of AAs@AAO nanochannels, allowing sensitive and precise sensing of CAP in complex food samples. The developed AAs@AAO nanochannel-based sensor showed a wide linear range from 0.32 to 1600 pg. mL^-1, low limit of detection (LOD) of 0.1 pg. mL^-1, high precision with relative standard deviation of 2.9%, and quantitative recoveries of 93.4-102.2% for CAP in milk, milk powder, and honey samples. This work proposes a versatile nanochannel-based platform for facile, sensitive, and precise sensing of hazardous residues in food samples.

Facile room temperature synthesis of ultra-small sized porous organic cages for fluorescent sensing of copper ion in aqueous solution

Facile synthesis of nano porous organic cages with small size and good fluorescence property is highly desirable, but still challenging and scarce for their sensing applications. Here we report a rapid room-temperature recrystallization method for the preparation of nano porous organic cages with ultra-small size as a fluorescent probe for copper ion. The prepared nano porous organic cages gave the diameter of 2.49 ± 0.04 nm, and exhibited stable emission at 535 nm with absolute quantum yield of 0.68%. On the basis of the coordination interaction and charge transfer between the nano porous organic cages and copper ion, a simple fluorescent probe for copper ion in aqueous solution was developed. The developed method gave a calibration function of QE = 0.4815lg[Cu²⁺] + 0.5847 (where QE is the quenching efficiency; [Cu²⁺] in μM) (R² = 0.9987) in a concentration range of 0.1-2 μM, the limit of detection (3s) of 8 nM, and the relative standard deviation of 0.36% for 10 replicate determinations of 0.5 μM copper ion. The recoveries of spiked copper ion in tap water samples ranged from 96.8% to 103.0%. The proposed method possesses good sensitivity, selectivity and accuracy.

Chiral covalent organic framework-monolith as stationary phase for high-performance liquid chromatographic enantioseparation of selected amino acids

The separation of amino acid (AA) enantiomers shows significance for chemistry, food, and biology, but remains challenging due to their similar properties. A promising nanoporous chiral covalent organic framework (COF) as a stationary phase for high-performance liquid chromatography (HPLC) suffers from the irregularity and widely distributed particle size of the chiral COF. Herein, we show the facile preparation of a chiral COF-monolith as a stationary phase for HPLC enantiomeric separation of AAs via orthogonal experiments. The CTzDa-monolith is prepared by the incorporation of the model chiral COF named CTzDa into the porous poly(ethylene dimethacrylate-co-methacrylate) monolith and reveals great permeability and mechanical stability. The corresponding CTzDa-monolithic column gives better chiral HPLC separation of AAs than the commercial Poroshell 120 chiral-T column. Thermal dynamic analysis and molecular docking calculations imply the involvement of stereoscopic hydrogen, π-π, and van der Waals interactions between the CTzDa and AAs during HPLC enantioseparation. The facile incorporation of the chiral COF into the porous monolith will promote the potential of a chiral COF as a stationary phase for HPLC.

Fabrication of G-quadruplex/porphyrin conjugated gold/persistent luminescence theranostic nanoprobe for imaging-guided photodynamic therapy

Photodynamic therapy (PDT) received great attention in cancer therapy due to the advantages of negligible drug resistance, low side effects, and minimal invasiveness. Development of theranostic nanoprobes with specific imaging-guided PDT is of great significance in the field. Herein we report the fabrication of a novel theranostic nanoprobe porphyrin/G-quadruplex conjugated gold/persistent luminescence nanocomposites for imaging-guided PDT. The developed nanoprobe contains NIR-emitting persistent luminescent nanoparticles (PLNP) as the core for autofluorescence-free bioimaging and Au coating on PLNP for facile subsequent DNA conjugation. The DNA sequence is designed to contain G-rich AS1411 aptamer for recognizing the over-expressed cellular nucleolin of cancer cell and forming a G-quadruplex structure to combine with tetrakis (4-carboxyphenyl) porphyrin (TCPP) to realize PDT. The AS1411 aptamer-contained DNA conjugated Au-coated PLNP is rapidly prepared via a freezing method with high content of DNA and good aqueous stability. Meanwhile, TCPP is easily loaded into the G-quadruplex structure formed from G-rich AS1411 aptamer on the surface of Au/PLNP in presence of K⁺. The theranostic nanoprobe gives integrated merits of PLNP for autofluorescence-free bioimging, TCPP for PDT and AS1411 aptamer-contained DNA for specific binding to cancer cells. This work provides a new specially designed imaging-guided PDT nanoplatform for theranostics.

Conjugation-regulating synthesis of high photosensitizing activity porphyrin-based covalent organic frameworks for photodynamic inactivation of bacteria

Preparation of porphyrin-based covalent organic frameworks (Por-COFs) with high photosensitizing activity for photodynamic inactivation of bacteria is of great challenge, but significant for economy and human health. Herein, we show a conjugation-regulating strategy to design and synthesize Por-COFs with high photosensitizing activity for the photodynamic inactivation of bacteria. Terephthalaldehyde (Da), 2,5-Dihydroxyterephthalaldehyde (Dha), and 2,5-Diethoxyterephthalaldehyde (Deta) with different conjugation degrees are selected to condense with 5,10,15,20-Tetrakis(4-aminophenyl)porphyrin (Tph) to synthesize COF-366, DhaTph, and JNU-2, respectively. The higher conjugation of Dha and Deta than Da leads to the higher conjugation of DhaTph and JNU-2, respectively. Moreover, the hydroxyl group in Dha and the ethoxy group in Deta further expand the conjugation of DhaTph and JNU-2 via the formation of intralayer extended π-cloud delocalization and p-π conjunction, respectively. The extension of conjugation for DhaTph and JNU-2 results in the increase of intersystem crossing process and significantly improves their photosensitizing activity. Furthermore, JNU-2 with the highest photosensitizing activity exhibits superior antibacterial effects toward Staphylococcus aureus (99.1%) and Escherichia coli (96.8%). This study offers a new conjugation-regulating strategy for designing high photosensitizing activity of Por-COFs for the inactivation of bacteria.

The experiences of foreign-educated nurses in Japan: a systematic review

AIM

To conduct a systematic review to understand the experiences of foreign-educated nurses in Japan.

BACKGROUND

The experiences of foreign nurses in host countries, and the challenges they face, have been widely investigated around the world. However, no systematic review has focused on the experience of foreign-educated nurses in Japan.

METHODS

A systematic literature review was conducted by following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Guidelines. Japan Medical Abstract Society, Citation Information by National Institute of Informatics, Cumulative Index to Nursing and Allied Health Literature, and PubMed databases were used for the literature search. Inclusion criteria were research articles published between 2013 and 2020 written in Japanese or English. A quality assessment was performed using Version 2018 of the Mixed Methods Appraisal Tool. Selected articles were read repeatedly, and relevant contents were extracted and summarized thematically.

RESULTS

Twenty-five studies were selected for the review. The themes generated included (1) reasons for nurses to come to Japan, (2) experiences and current situations among the Economic Partnership Agreement nurses/nurse candidates living in Japan, and (3) experiences and current situation of nurses who had returned to their home countries. The second theme was classified into four categories: language and communication barriers, low pass rates for the national qualification exam, adaptation to workplaces and social environments, and psychological distress.

CONCLUSION

Foreign nurses in Japan face various challenges and difficulties, even after they return to their home countries. Solving these problems may improve the wellbeing of foreign-educated nurses in Japan.

IMPLICATIONS FOR NURSING POLICY

The results from the current review highlight the necessity for immediate intervention by policymakers to improve the current support system for Economic Partnership Agreement nurses/nurse candidates. A thorough pre-arrival orientation should be provided for the nurse candidates to able them to make a well-informed choice.

Room-temperature preparation of a chiral covalent organic framework for the selective adsorption of amino acid enantiomers

Herein, we have reported the facile room-temperature synthesis of a chiral covalent organic framework (CCOF) for the enantioselective adsorption of amino acids. The prepared CCOF provides various stereoscopic interactions with amino acids for highly selective adsorption of their enantiomers.

Thiol-Ene Click Synthesis of Phenylboronic Acid-Functionalized Covalent Organic Framework for Selective Catechol Removal from Aqueous Medium

We report a thiol-ene click strategy for the preparation of a novel phenylboronic acid-functionalized covalent organic framework (COF) for selective removal of catechol in aqueous solution. Vinyl-functionalized 2,5-diallyloxyterephthalaldehyde (Da-V) was prepared as a building ligand. Da-V was then condensed with 1,3,5-tris(4-aminophenyl)benzene (Tab) to give a vinyl-functionalized COF DhaTab-V. Subsequently, 4-mercaptophenylboronic acid (4-MPBA) was covalently linked on DhaTab-V via thiol-ene click reaction to give phenylboronic acid-functionalized COF DhaTab-PBA. The adsorption isotherms, energetics and kinetics, and reusability of DhaTab-PBA for the adsorption and removal of catechol from aqueous solution were investigated in detail. This phenylboronic acid-functionalized COF is promising as sorbent for selective removal of catechol from aqueous medium with large adsorption capacity and good reusability.

DNA damage-induced activation of ATM promotes β-TRCP-mediated ARID1A ubiquitination and destruction in gastric cancer cells

Background

AT-rich interactive domain-containing protein 1A (ARID1A) is a subunit of the mammary SWI/SNF chromatin remodeling complex and a tumor suppressor protein. The loss of ARID1A been observed in several types of human cancers and associated with poor patient prognosis. Previously, we have reported that ARID1A protein was rapidly ubiquitinated and destructed in gastric cancer cells during DNA damage response. However, the ubiquitin e3 ligase that mediated this process remains unclear.

Materials and methods

The interaction between ARID1A and β-TRCP was verified by co-immunoprecipitation (Co-IP) assay. The degron site of ARID1A protein was analyzed by bioinformatics assay. Short hairpin RNAs (shRNAs) were used to knockdown (KD) gene expression.

Results

Here we show that DNA damage promotes ARID1A ubiquitination and subsequent destruction via the ubiquitin E3 ligase complex SCFβ-TRCP. β-TRCP recognizes ARID1A through a canonical degron site (DSGXXS) after its phosphorylation in response to DNA damage. Notably, genetic inactivation of the Ataxia Telangiectasia Mutated (ATM) kinase impaired DNA damage-induced ARID1A destruction.

Conclusions

Our studies provide a novel molecular mechanism for the negative regulation of ARID1A by β-TRCP and ATM in DNA damaged gastric cancer cells.

Covalent immobilization of covalent organic framework on stainless steel wire for solid-phase microextraction GC-MS/MS determination of sixteen polycyclic aromatic hydrocarbons in grilled meat samples

Covalent organic framework TpBD was grafted on stainless steel wire with polydopamine as a linker. The fabricated TpBD bonded stainless steel wire was used as the solid-phase microextraction fiber to extract sixteen polycyclic aromatic hydrocarbons (PAHs) for subsequent GC-MS/MS determination in grilled meat samples. The developed method gave the limits of detection (S/N = 3) from 0.02 (pyrene)-1.66 (naphthalene) ng L^-1 and enhancement factors from 1069 (naphthalene)-10879 (benz(a)anthracene). The relative standard deviations (RSDs) for intra-day and inter-day study are in the range of 2.6%-8.5% and 4.5%-9.4%, respectively. The fiber-to-fiber RSDs for three parallel prepared fibers were 5.3%-10.0%. One TpBD bonded fiber can stand at least 200 cycles without significant loss of extraction efficiency. The developed method was successfully applied for the determination of trace PAHs in grilled meat samples with recoveries from 85.1% to 102.8%.

Author Correction: Bottom-up synthesis of chiral covalent organic frameworks and their bound capillaries for chiral separation

This Article contains an error in Fig. 1, in which the structures of '(+)-Ac-L-Ta' and 'CTp' are drawn incorrectly. The correct version of Fig. 1 is shown below. The error has not been fixed in the original PDF and HTML versions of the Article.

[Analysis on influencing factors of deaths from severe heat stroke in Shanghai, 2013-2017]

Objective: To explore the related factors of death from severe heat stroke in Shanghai from 2013 to 2017. Methods: The data of 1 152 patients with severe heat stroke who were divided into survival (n=1 037) and death (n=115) groups including gender, age and heat stroke type (heat cramp, heat exhaustion, heat apoplexy and the mixed type) were collected from meteorological bureau and case report system for high temperature heat stroke in Shanghai from 2013 to 2017. Meanwhile, the meteorological data of the onset date of severe heat stroke cases were collected, including maximum temperature, minimum temperature, daily temperature, relative humidity, air pressure, precipitation and wind speed. The differences of individual and meteorological factors between the two groups were compared, and multivariate logistic regression model was used to analyze the related factors of death from severe heat stroke. Results: Among 1 152 cases, the mean±SD of age was (56.29±18.95) years old, 843 (73.18%)were male, 962 (83.51%) were in the heat wave period; 322 cases (27.95%) were heat cramp, 170 cases (14.76%) were heat exhaustion, 533 cases (46.27%) were heat apoplexy and 114 cases (9.90%) were the mixed type. Daily average temperature ((32.81±1.99) ℃), daily maximum and minimum temperatures ((38.20±2.24) ℃ and (29.22±1.94) ℃) in survival group were lower than those in death group (all P values<0.001), which were (33.76±1.17) ℃, (39.19±1.31) ℃ and (29.72±1.66) ℃. Daily average relative humidity ((60.36±9.75)%) and daily minimum relative humidity ((41.26±9.71)%) in survival group were higher than those in death group(allP values <0.05), which were (54.59±6.89)% and (35.60±7.24)%. The results of logistic regression analysis suggested that compared with the cases with daily average humidity <60% and a mixed type heat stroke, the death OR (95%CI) values of cases with daily average humidity >60%, heat cramp, heat exhaustion and heat apoplexy were 0.31 (0.18,0.54), 0.13 (0.05,0.34), 0.68 (0.58,2.30) and 0.87 (0.48,1.58). Conclusion: The temperature, relative humidity and the type of heat stroke were the main related factors affecting the prognosis of severe heat stroke.

[Effects of MTA1 on biological behaviors of gastric cancer cells]

Objective: To study the effects of metastasis associated 1 (MTA1) on biological characteristics such as migration, invasion and proliferation of gastric cancer (GC) cells. Methods: pSilencer3.1-MTA1-siRNA vector was used to establish human gastric cancer BGC-823 cell lines with constitutive MTA1-knockdown. Boyden, wound healing, clony forming assay and 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2H tetrazolium bromide (MTT) assay were performed to identify the effects of MTA1-deficiency on the biological behaviors of BGC-823 cells in vitro. Simultaneously, MTA1 overexpressed BGC-823 cell line was established by pcDNA3-MTA1 plasmid transfection for reverse verification. In addition, the role of MTA1 in the tumorigenicity of gastric cancer BGC823 cells in vivo was examined by subcutaneous injection of BGC-823 cells expressing different MTA1 levels into nude mice. Reverse transcription-polymerase chain reaction (RT-PCR) and western blot were used to detect the expression levels of integrin β1, cyclin D1 and uPAR in pSilencer3.1-MTA1-siRNA, pcDNA3-MTA1 transfected cells and control cells. Results: MTA1 knocked down or upregulated BGC-823 cell lines were successfully generated by transfecting pSilencer3.1-MTA1-siRNA or pcDNA3-MTA1 vector with lipofectamine 2000, respectively. The Boyden and wound healing experiments showed metastasis and invasion ability in MTA1 knocked down cells (25±2, 12±1) were significantly decreased when compared with those of control (78±2, 50±2) and MTA1-overexpressed groups (218±2, 269±3; P<0.05). The results of MTT assay and colony forming assay were significantly decreased when compared with those of showed that MTA1 overexpressed cells grew more rapidly and formed more colonies in vitro and induced worse malignant tumors in vivo, while MTA1 knocked down cells presented the reversed phenotype[control group (1 482.41±511.90) mm(3,) (1.39±0.29)g; MTA1 overexpressed group [(3 158.73±1 823.22) mm(3,) (2.23±0.51)g; MTA1-downregulated group (711.32±284.30)mm(3,) (0.87±0.21) g ; P<0.05)]. In addition, RT-PCR result showed that the expression level of MTA1 was positively correlated with the known metastasis-related genes (integrinβ1, cyclinD1, uPAR). Conclusions: MTA1 promotes the invasion, migration and proliferation of human gastric cancer BGC-823 cells. On the contrary, down-regulation of MTA1 significantly inhibits tumorigenicity of BGC-823 cells and induces favorable phenotypes. MTA1 may promote the malignant phenotype of BGC-23 cells via regulating the expressions of integrinβ1, cyclinD1 and uPAR.

Transarterial embolization and low-dose continuous hepatic arterial infusion chemotherapy with oxaliplatin and raltitrexed for hepatocellular carcinoma with major portal vein tumor thrombus

AIM

To determine the efficacy and safety of transarterial embolization and low-dose continuous hepatic arterial infusion chemotherapy with oxaliplatin and raltitrexed in hepatocellular carcinoma (HCC) with major portal vein tumor thrombus (MPVTT).

METHODS

Eighty-six patients with MPVTT accepted routine embolization. The catheter was kept in the hepatic artery and oxaliplatin (50 mg in 250 mL of glucose) was infused by pump for 4 h, followed by raltitrexed (2 mg in 100 mL of 0.9% saline) infusion by pump for the next 1 h. The efficacy and safety were evaluated after the transarterial chemoembolization (TACE).

RESULTS

Full or partial embolization was achieved in 86 cases, where all the cases received low dose continuous hepatic arterial infusion chemotherapy. Complete responses (CRs), partial responses (PRs), stable disease (SD), and disease progression (PD) for intrahepatic disease were observed in 0, 45, 20, and 21 patients, respectively. The 1-, 2-and 3-year overall survival rates of the 86 patients were 40.7%, 22.1%, and 8.1% respectively, and the median survival time was 8.7 mo. Complication was limited.

CONCLUSION

TACE with low dose continuous hepatic arterial infusion of oxaliplatin and raltitrexed could be an option in MPVTT patient; it was shown to be effective in patients with advanced HCC with MPVTT with less toxicity.

Advances in covalent organic frameworks in separation science

Covalent organic frameworks (COFs) are a new class of multifunctional crystalline organic polymer constructed with organic monomers via robust covalent bonds. The unique properties such as convenient modification, low densities, large specific surface areas, good stability and permanent porosity make COFs great potential in separation science. This review shows the state-of-the art for the application of COFs and their composites in analytical separation science. COFs and their composites have been explored as promising sorbents for solid phase extraction, potential coatings for solid phase microextraction, and novel stationary phases for gas chromatography, high-performance liquid chromatography and capillary electrochromatography. The prospects of COFs for separation science are also presented, which can offer an outlook and reference for further study on the applications of COFs.

Layer-by-layer preparation of 3D covalent organic framework/silica composites for chromatographic separation of position isomers

A layer-by-layer approach was developed to fabricate COF-300@SiO₂ for HPLC separation of position isomers.

High-Crystallinity Covalent Organic Framework with Dual Fluorescence Emissions and Its Ratiometric Sensing Application

High crystallinity of covalent organic frameworks (COFs) with dual fluorescence emissions has not been reported so far. Here, we show the rational design and preparation of high-crystallinity COF TzDa via the synergetic interaction of docking sites and hydrogen bonds: 4,4',4″-(1,3,5-Triazine-2,4,6-triyl)trianiline (Tz) with the docking site and 2,5-dihydroxyterephthalaldehyde (Da) with the OH group are employed to synthesize the imine-linked two-dimensional high-crystallinity layered structure TzDa. The prepared mesoporous TzDa (ca. 36 Å) exhibits high thermal and chemical stability. The intramolecular charge transfer (ICT) and excited-state intramolecular proton transfer (ESIPT) effects bring TzDa two main fluorescence emissions around 500 and 590 nm. Water molecules can interfere with the ICT and ESIPT effects, allowing the development of a ratiometric fluorescent sensor for water in organic solvents. The proposed sensor shows high sensitivity to trace water in conventional organic solvents. The high stability of TzDa allows its recyclable uses for trace water detection. This work not only offers a platform for the construction of high-crystallinity COFs, but also provides a rational design of COFs with dual fluorescence emissions for ratiometric sensing applications.

[Acute effect of ambient air pollution on small airway lung functions among school children in Shanghai]

Objective: To study the acute effects of compound ambient air pollution on small airway lung functions among school children in Shanghai. Method: A longitudinal survey on lung functions was conducted among 233 school-children from three schools (A, B and C, located in innerring, mid-ring and outer-ring areas). Lung function test was performed once a week for 3 times respectively, among children in school A and B in Dec. 2013 and in school C in Dec. 2014. The fourth lung function test was tested in Jun. 2014 and May 2015 in the respective schools. Results: from the lung function would include items as: forced mid-expiratory flow at 25% of forced vital capacity (MEF(25%)), mid-expiratory flow at 50% of forced vital capacity (MEF(50%)), mid-expiratory flow at 75% of forced vital capacity (MEF(75%)) and mid-expiratory flow between 25% and 75% of the forced vital capacity (FEF(25%-75%)). Data regarding the daily air quality real-time of PM(2.5), PM(10), SO(2) and NO(2) in Dec. 2013, Dec. 2014, Jun. 2014 and May. 2015 from the three environmental monitoring spots and meteorological data from the Shanghai Meteorological Service system which were physically close to the three schools, were collected simultaneously. Linear mixed effect model was used to examine the levels of correlation between lung function indicators and ambient air pollutants. Results When confounding factors on meteorology and individuals were controlled, the lag effects and accumulated lag effects were found to have existed between the internal quarter rang (IQR) concentration of PM(2.5) and PM(10) in lag2 day and lag02 days, IQR concentration of SO(2) in lag02 day and IQR concentration of NO(2) lag0 day, when small airway lung functions like MEF(25%), MEF(50%), MEF(75%) and FEF(25%-75%)(P<0.05) were inspected. Results from the two air pollutants model analysis showed that SO(2) and NO(2) presenting interactive effects with PM(2.5), PM(10) and lag effects more significant than the individual SO(2) and NO(2), respectively (P<0.05). Conclusion: Contents on the ambient air pollutants as PM(2.5), PM(10), SO(2) and NO(2) were negatively associated with the lung functions in the small airways of children, in Shanghai.

Bottom-up synthesis of chiral covalent organic frameworks and their bound capillaries for chiral separation

Covalent organic frameworks (COFs) are a novel class of porous materials, and offer great potential for various applications. However, the applications of COFs in chiral separation and chiral catalysis are largely underexplored due to the very limited chiral COFs available and their challenging synthesis. Here we show a bottom-up strategy to construct chiral COFs and an in situ growth approach to fabricate chiral COF-bound capillary columns for chiral gas chromatography. We incorporate the chiral centres into one of the organic ligands for the synthesis of the chiral COFs. We subsequently in situ prepare the COF-bound capillary columns. The prepared chiral COFs and their bound capillary columns give high resolution for the separation of enantiomers with excellent repeatability and reproducibility. The proposed strategy provides a promising platform for the synthesis of chiral COFs and their chiral separation application.

Porous materials can be used in columns for gas separation applications. Here, Yan and co-workers from a bottom-up method have produced chiral covalent organic frameworks and from an in situ strategy formed capillary columns for chiral gas chromatography.

The expression of angiopoietin-1 and -2 in the endometrium of women with abnormal bleeding induced by an intra-uterine device

This study identified differences in expression of angiopoietin-1 (Ang-1) and angiopoietin-2 (Ang-2) in the endometrium of 33 women with abnormal bleeding induced by an intra-uterine device (IUD; 23 proliferative phase, 10 secretory phase) compared with 28 control samples from normal endometria in women without an IUD fitted (12 proliferative phase, 16 secretory phase). Expression of Ang-1, Ang-2 and endothelial cell-specific tyrosine kinase receptor-2 (Tie-2) mRNA was detected by reverse transcription-polymerase chain reaction (RT-PCR), and Ang-1 and Ang-2 protein levels were detected by immunohistochemistry. The RT-PCR results showed significantly decreased Ang-1 expression in the endometrium from IUD patients during both phases compared with the control women. Expression of Tie-2 mRNA and the Ang-1:Ang-2 mRNA ratio were also significantly decreased in endometria from IUD patients in the secretory phase compared with the control women. Immunohistochemical analysis showed elevated Ang-2 protein levels in secretory phase endometrium from IUD patients compared with the control women. These results suggest that the angiopoietin/Tie-2 system promotes vascular remodelling in the endometrium and that changes in the expression of Ang-1, Ang-2 and Tie-2 may contribute to abnormal uterine bleeding in some IUD users.

[The role of Anopheles anthropophagus in malaria transmission in in Xinyang City of Henan Province]

OBJECTIVE

To study the role of Anopheles anthropophagus in malaria transmission and transmission threshold so as to provide basis for vector surveillance and malaria control strategy.

METHODS

Parasitological and entomological methods were used in the investigation at 5 villages of Xinyang City, Henan Province.

RESULTS

From July to August, 1999, 74 febrile cases (10.9% of the total population) were examined. Among them 50 were infected, the incidence in the population of surveyed spots was 7.4%. Active detection was made in another randomly selected two villages and found that the parasite rate in the inhabitants was 2.0%, and the positive rate of IFA was 8.4%. Only vivax malaria was detected. An. anthropophagus and An. sinensis were collected, with An. anthropophagus as the predominant one in human dwellings. The estimated man-biting rate and the human blood index were 4.9388 and 0.7858 respectively. The vectorial capacity of An. anthropophagus was 5.5296. The critical man-biting rate of An. anthropophagus was 0.2407 as calculated by the formula (ma = -rlnP/abPh) according to Macdonald's model. The local man-biting rate was 20 times higher than that of the critical man-biting rate.

CONCLUSION

The results demonstrated that An. anthropophagus is the principal vector in malaria transmission in the area. The findings imply that the critical man-biting rate is of practicable importance in vector surveillance.

Study of simplified measures for malaria surveillance in the late consolidation phase in China

This paper presents the results of a study on simplified surveillance methods conducted in 23 pilot counties in 11 provinces and municipalities in China where reside 15 million people and malaria control has been in the late consolidation phase. Two simplified surveillance Schemes (A and B) taking treatment of clinical cases as the main measure were implemented in 1992-1994. The rate of annual blood examination for case detection was 1.0% in pilot Scheme A, while in areas of scheme B it was 0.3%. The implementation of both Scheme A and Scheme B, simplified or without treatment of infection foci and management of mobile populations, acquired satisfactory effects against malaria. Consequently, malaria incidence was declining steadily, only a few indigenous and introduced cases were detected. The parasite rate in residents and the IFA positive rate in children were very low. The results of pilot studies and cost-effectiveness analysis indicated that Scheme B is effective, rational and economic, and can be implemented to replace the routine surveillance measures in areas where malaria has been at the late consolidation phase in China.

Malaria and its control in the People's Republic of China

Malaria is one of the major parasitic diseases in China. During the past 40 years, large scale malaria control activities were conducted in the country relying on primary health care nets and community participation. The control of malaria was implemented according to the principles of adopting integrated measures and repeated practices which are characterized by time- and locality-oriented approaches. As a result, remarkable success has been achieved. By the end of 1990, there were 117,000 malaria cases in China, with a morbidity of 0.0106%, which dropped by 95% in comparison with that in the 1950s. Most of the original hyper-endemic areas became meso- or hypo-endemic and for most of the previously meso- or hypo-endemic areas, the disease became sporadic. Malaria distribution and epidemic patterns also demonstrated great changes. The major experience comprises the integration of the malaria control program into the overall national health program, the mobilization of various sectors, including the community, the investigators and technical personnel in research institutions and control services to participate and cooperate in solving problems and difficulties encountered.