HpaII-assisted and linear amplification-enhanced isothermal exponential amplification fluorescent strategy for rapid and sensitive detection of DNA methyltransferase activity.

The detection of methyltransferase (MTase) activity is of great significance in methylation-related disease diagnosis and drug screening. Herein, a HpaII-assisted and linear amplification-enhanced exponential amplification strategy is proposed for sensitive and label-free detection of M.SssI MTase activity. The P1 probe contains self-complementary sequence 5'-CTAGCCGGCTAG-3' at 3'-terminal. After denaturation and annealing, P1 probes hybridize with itself to generate P1 duplexes. M.SssI MTase induces methylation of cytosine at 5'-CG-3' in P1 duplexes, and thus, HpaII fails to cleave at 5'-CCGG-3' due to methylation sensitivity, leaving P1 duplex intact. Then, these intact P1 duplexes are extended along 3'-terminal through Vent (exo-) DNA polymerase to generate dsDNA, which is recognized and nicked at the recognition sites by Nt.BstNBI, releasing two copies of primer X. Primer X hybridizes with X' at the amplification template T1 (X'-Y'-X') and then serves as primers to trigger the exponential amplification reaction (EXPAR). The point of inflection (POI) values of real-time fluorescence curves is linearly correlated with the logarithm of M.SssI MTase concentration in the range of 0.125 [Formula: see text] 8 U mL-1 with a low detection limit of 0.034 U mL-1. In the absence of M.SssI, P1 duplexes are cut by HpaII and separated into ssDNA under the executed temperature of EXPAR and thus unable to trigger the amplification. The strategy provides good selectivity against other types of MTases and protein and is able to detect M.SssI activity in human serum. Furthermore, the analytical method has the generality and can be extended to the analysis of other types of DNA MTases.

Protective effect of vitamin C against tetrachlorobenzoquinone-induced 5-hydroxymethylation-dependent apoptosis in HepG2 cells mainly via the mitochondrial apoptosis pathway.

Tetrachlorobenzoquinone (TCBQ) is an active metabolite of pentachlorophenol, and stimulates the accumulation of ROS to trigger apoptosis. The preventive effect of vitamin C (Vc) against TCBQ-induced apoptosis in HepG2 cells is unknown. And there is little known about TCBQ-triggered 5-hydromethylcytosine (5hmC)-dependent apoptosis. Here, we confirmed that Vc alleviated TCBQ-induced apoptosis. Through investigating the underlying mechanism, we found TCBQ downregulated 5hmC levels of genomic DNA in a Tet-dependent manner, with a particularly pronounced decrease in the promoter region, using UHPLC-MS-MS analysis and hydroxymethylated DNA immunoprecipitation sequencing. Notably, TCBQ exposure resulted in alterations of 5hmC abundance to ∼91% of key genes at promoters in the mitochondrial apoptosis pathway, along with changes of mRNA expression in 87% of genes. By contrast, 5hmC abundance of genes only exhibited slight changes in the death receptor/ligand pathway. Interestingly, the pretreatment with Vc, a positive stimulator of 5hmC generation, restored 5hmC in the genomic DNA to near-normal levels. More notably, Vc pretreatment further counter-regulated TCBQ-induced alteration of 5hmC abundance in the promoter with 100% of genes, accompanying the reverse modulation of mRNA expressions in 89% of genes. These data from Vc pretreatment supported the relationship between TCBQ-induced apoptosis and the altered 5hmC abundance. Additionally, Vc also suppressed TCBQ-stimulated generation of ROS, and further increased the stability of mitochondria. Our study illuminates a new mechanism of TCBQ-induced 5hmC-dependent apoptosis, and the dual mechanisms of Vc against TCBQ-stimulated apoptosis via reversely regulating 5hmC levels and scavenging ROS. The work also provided a possible strategy for the detoxification of TCBQ.

Aggregation-induced emissive copper(I) complexes for living cell imaging.

Phosphorescent binuclear copper(I) complexes [Cu2(BrphenBr)2(Ph2P(CH2)nPPh2)2](ClO4)2 with different conformations are obtained by reaction of [Cu(NCCH3)4]ClO4, 3,8-dibromo-1,10-phenanthroline (BrphenBr), and corresponding diphosphine ligands, where n = 1, 4, 5, and 6 in complexes Cu-1, Cu-2, Cu-3, and Cu-4, respectively. Complex Cu-4 exhibits both the eclipsed and the staggered conformations of 18-membered Cu2C12P4 metallacycles in a 1:1 ratio in the crystal structure. All complexes are very stable to air and moisture in the solid state because of the high level of protection of all the Cu(I) centers, N and P atom centers resulting from the close contact of BrphenBr and diphosphine ligands, and what is more important is that there exist very soft P donors and the chelating effect of aromatic N atoms. The ESI-MS result through changing the collision cell energy from 0 to 20 eV suggests that the corresponding [Cu2(Ph2P(CH2)nPPh2)2](2+) cations are the thermodynamically stable species, while [Cu2(BrphenBr)2(Ph2P(CH2)nPPh2)2](ClO4)2 are stable products in crystallization kinetics in solutions. All complexes Cu-1-Cu-4 display good aggregation-induced phosphorescence emission (AIPE) behavior in CH2Cl2/hexane mixed solvents, which are suggested to arise from restriction of intramolecular rotation. Aggregation-induced emission (AIE) of complexes Cu-1-Cu-4 in PBS/DMSO (99:1, v:v) is used for living HeLa cell imaging successfully with green intracellular emission image.

Fabrication of molecularly imprinted carbon nanotubes integrating ionic liquids for efficient detection of perfluoroalkyl carboxylic acid in environmental water.

It is extremely significant while challenging to accurately detect low-levels of perfluoroalkyl carboxylic acid compounds (PFCAs) in environmental water. Herein, adopting perfluorotetradecanoic acid as the dummy template, selective molecularly imprinted composites (CNTs@ILs@MIPs) grafted carbon nanotubes integrating hydrophilic ionic liquids were successfully prepared via surface imprinting and dummy-template imprinting techniques. The obtained CNTs@ILs@MIPs were applied as selective extraction adsorbent for specifically extract PFCAs in environmental water coupled with gas chromatography-mass spectrometry quantification. Detailed studies were conducted on the main preparation parameters and extraction conditions. The CNTs@ILs@MIPs displayed excellent adsorptivity, and the established method exhibited low LODs (0.60-1.64 ng L-1), wide linearity with R2 above 0.9994, and satisfactory adsorption recoveries (80.5-112.5%) for seven PFCAs. This proposed method provides a new applicable approach for the detection of targeted pollutants in environmental water by utilizing the high affinity and recognition ability of molecularly imprinted carbon nanotube functional materials modified with ionic liquids.

Sensitive extraction of seven pesticide residues from environmental water with magnetic graphene oxide-based covalent organic framework.

The use of pesticides has increased with the development of agriculture. However, due to the trace content and the matrix's inherent complexity in environmental water, development of rapid and sensitive detection method present significant challenges in the analysis of pesticide residues. The study synthesized magnetic graphene oxide (MGO) by combining superparamagnetic nanoparticles with the easy modification of graphene oxide (GO). Covalent organic frameworks (COFs) were then modified to have a large specific surface area. Finally, magnetic graphene oxide-based covalent organic frameworks, namely MGO-COFs, were obtained with a spherical structure and used as magnetic solid-phase extraction materials, which was successfully used to determine the seven pesticide residues in environmental samples in conjunction with high performance liquid chromatography. The method has a wide linear range for the tested pesticides, with satisfactory correlation coefficients (R ≥ 0.099) and low detection limits (0.3-1.21 µg L-1). The correlation coefficients for all seven pesticides were high (R2 ≥ 0.9996). The spiked recoveries, exhibiting a range of 91.3 to 109 %, demonstrated that the developed MGO-COF-MSPE-HPLC-UV method is simple, efficient, and suitable for the analysis and detection of seven pesticide residues in environmental water.

Solvent-induced terbium metal-organic frameworks for highly selective detection of manganese(ii) ions.

Highly selective detection of trace metal ions has become one of the most urgent issues in public security and living systems. Developing a highly efficient fluorescent sensor for manganese(ii) (Mn2+) ions is a huge challenge. Herein, by utilizing the solvent regulation approach, a pair of terbium metal-organic frameworks (UPC-36, [Tb2(btdc)3(DMF)(H2O)4]·DMF and UPC-37, [Tb2(btdc)3(H2O)6]) based on a π-electron-rich ligand (H2btdc = 2,2'-bithiophene-5,5'-dicarboxylic acid) has been chosen as highly efficient sensors for the selective detection of Mn2+ ions. Interestingly, the fluorescence of UPC-36 can be quenched by Mn2+, Cu2+, Al3+, Cr3+ and Fe3+ ions, while UPC-37 can only be quenched by Mn2+ ions. For detecting Mn2+ ions, the limit of detection (LOD) values are calculated to be 0.813 mM and 0.715 mM for UPC-36 and UPC-37 respectively. According to the ICP results, UPC-37 has stronger interactions with Mn2+ ions because of the more regular arrangement of ligands existing in UPC-37, so it exhibits a high sensitivity and selectivity (Ksv = 5.25 × 105 M-1).

A non-interpenetrating lead-organic framework with large channels based on 1D tube-shaped SBUs.

This work presents the construction of a porous lead-organic framework (UPC-10) with large channels of ∼24 Å. UPC-10 shows efficient adsorption of I2 and selective adsorption of some dyes containing the SO3- group. After the adsorption of dyes, UPC-10 exhibits a CO2 gas uptake ability. Furthermore, UPC-10 could be transformed into PbS in a H2S atmosphere, and the derived PbS manifests N2 and CO2 uptake abilities.

Cyclodextrin-Based Metal-Organic Nanotube as Fluorescent Probe for Selective Turn-On Detection of Hydrogen Sulfide in Living Cells Based on H2S-Involved Coordination Mechanism.

Hydrogen sulfide (H2S) has been considered as the third biologically gaseous messenger (gasotransmitter) after nitric oxide (NO) and carbon monoxide (CO). Fluorescent detection of H2S in living cells is very important to human health because it has been found that the abnormal levels of H2S in human body can cause Alzheimer's disease, cancers and diabetes. Herein, we develop a cyclodextrin-based metal-organic nanotube, CD-MONT-2, possessing a {Pb14} metallamacrocycle for efficient detection of H2S. CD-MONT-2' (the guest-free form of CD-MONT-2) exhibits turn-on detection of H2S with high selectivity and moderate sensitivity when the material was dissolved in DMSO solution. Significantly, CD-MONT-2' can act as a fluorescent turn-on probe for highly selective detection of H2S in living cells. The sensing mechanism in the present work is based on the coordination of H2S as the auxochromic group to the central Pb(II) ion to enhance the fluorescence intensity, which is studied for the first time.