摘要：
Developing a reliable fluorescence probe is crucial for accurately monitoring sodium dithionite (Na2S2O4, SDT) in biosystems, but the current reported azo-based ones suffers from short excitation/emission wavelengths and relative slow response speed. To address this issue, we herein present a novel near-infrared emissive fluorescence probe for SDT, namely DCM-MQ, consisting of a dicyanomethylene-benzopyran fluorogenic reporter and a 1-methylquinolinium as recognition moiety. On the basis of the specific reduction mechanism, DCM-MQ exhibited a rapid colorimetric and fluorescent recognition for SDT (less than 3 s) with large Stokes shift (112 nm) and high sensitivity (detection limit was 19 nM). The fluorescence imaging results demonstrate that DCM-MQ is competent for monitoring SDT in living systems. (C) 2020 Elsevier B.V. All rights reserved.
通讯机构：
[Lin Yuan] S;State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, P. R. China
摘要：
Herein, a novel two-photon ratiometric fluorescence assay was proposed for monitoring endogenous steroid sulfatase (STS) activity, which could be applied for the ratiometric imaging of STS activity in the endoplasmic reticulum of living cells and tissues and also could be used to distinguish estrogen-dependent tumor cells from other types of cells.
摘要：
For the first time it isdemonstrated that sulfhydryl compounds can suppress longitudinal etching of gold nanorods via consuming oxidizers, which provides a new signaling mechanism for colorimetric sensing. As a proof of concept, a colorimetric assay is developed for detecting organophosphorus pesticides, which are most widely used in modern agriculture to improve food production but with high toxicity to animals and the ecological environment. Triazophos was selected as a model organophosphorus pesticide. In the absence of triazophos, the active acetylcholinesterase can catalyze the conversion of acetylthiocholine iodide to thiocholine whose thiol group can suppress the I(2)-induced etching of gold nanorods. When triazophos is present, the activity of AchE is inhibited, and I(2)-induced etching of gold nanorods results in triazophos concentration-dependent color change from brown to blue, pink, and red. The aspect ratio of gold nanorods reduced with gradually blue-shifted longitudinal absorption. There was a linear detection range from 0 to 117nM (R(2) = 0.9908), the detection limit was 4.69nM, and a good application potential was demonstrated by theassay of real water samples. This method will not only contribute to public monitoring of organophosphorus pesticides but also has verified a new signaling mechanism which will open up a new path to develop colorimetric detection methods. It has been first found that sulfhydryl compounds can suppress longitudinal etching of gold nanorods (AuNRs) via consuming oxidizers, which provides a new signaling mechanism for colorimetric sensing. As a proof of concept, a colorimetric assay is developed for sensitively detecting organophosphorus pesticides (OPs). It will not only contribute to public monitoring of OPs but also has verified a new signaling mechanism which will open up a new path to develop multicolor colorimetric methods.
摘要：
Herein, we describe a novel two-photon excitation/red emission-based ratiometric pH nanosensor consisting of a pH-sensitive two-photon dye and Tm(3+)-doped upconversion nanoparticles (UCNP). The fluorescence emission ratio between the dye (610 nm) and UCNPs (810 nm) (I610/I810) provides a linear indicator of pH values in the range from pH 4.0 to 6.5 with high sensitivity. These nanoprobes selectively accumulate in the lysosomes of cells, making them suitable for lysosomal pH tracking. This pH nanoprobe has been successfully applied in visualizing chemically stimulated changes of intracellular pH in living cells and tissues.
摘要：
As VEGF mRNA is an endothelial cell-specific mitogen and a key regulator of angiogenesis in a variety of physiological and pathological processes, high expression levels of VEGF messenger RNA (mRNA) contribute to VEGF-driven angiogenesis in the hypoxic areas of solid tumors and then disrupt the vascular barrier, which may potentiate tumor cell extravasation. Thus, monitoring the changes in VEGF mRNA is necessary to understand the genetic programme under hypoxic conditions and thus facilitate risk assessment and risk reduction in hypoxic environments. Herein, a new fluorescent nanoprobe based on azoreductase-responsive functional metal-organic frameworks (AMOFs) was developed to realize the imaging of VEGF mRNA under hypoxic conditions. Since the azobenzene units in the AMOFs can be reduced to amines by the highly expressed azoreductase in an oxygen-deficient environment, the VEGF mRNA-targeted molecular beacon (MB), which is adsorbed on the surface of AMOFs via electrostatic interactions, can be released due to the structural damage of AMOFs. Moreover, TAMRA (carboxytetramethyl-rhodamine, donor) and Cy5 (acceptor) were close to each other due to the stem-loop conformation of MB, thus inducing high fluorescence energy resonance transfer (FRET) efficiency. Upon the addition of VEGF mRNA, the hybridization of VEGF mRNA destroyed the stem-loop conformation of MB, and then, the two fluorophores labeled on MB were separated with low FRET efficiency. This constructed fluorescent nanoprobe enables the quantitative analysis and in situ imaging of the VEGF mRNA level in living cells under hypoxic conditions. We expect that it will offer a potentially rich opportunity to understand the physiological processes of genetic programme.
摘要：
Lanthanides are very important for their unique catalytic, optical and magnetic properties. Various ligands have been synthesized to coordinate with lanthanides so that their properties can be better controlled enabling various analytical, materials and biomedical applications. DNA is an anionic polymer made of four types of nucleotides. With high stability, low cost, programmability, and molecular recognition and catalytic functions, DNA has become a very popular material in the past few decades. In recent years, both nucleotides and DNA have been explored as ligands for lanthanides. In this article, fundamental interactions between nucleotides and DNA with lanthanides are reviewed in terms of binding sites and thermodynamics. Further, coordination polymers formed by mixing nucleotides and lanthanides are discussed, which can form nanoparticles, fibers and hydrogels with applications for enzyme encapsulation, imaging and biosensors. DNA sequences have been screened to bind lanthanides and to sensitize luminescence of both Tb3+ and Eu3+. Lanthanides at millimolar concentrations can also serve as nuclease mimics to cleave both RNA and DNA. In addition, in vitro selections have resulted in a suite of new DNAzymes for site-specific RNA and DNA cleavage at much lower lanthanide concentrations. Overall, nucleotides and DNA are unique ligands for lanthanides and future work will likely be focused on understanding of fundamental coordination structures, rational design of advanced coordination materials, and expanding the range of DNA catalytic reactions that can be assisted by lanthanides. (C) 2019 Elsevier B.V. All rights reserved.
关键词：
amitrole;catalase;gold;herbicide;hydrogen peroxide;iodine;nanotube;chemistry;color;colorimetry;food contamination;limit of detection;metabolism;procedures;water pollutant;Amitrole;Catalase;Color;Colorimetry;Food Contamination;Gold;Herbicides;Hydrogen Peroxide;Iodine;Limit of Detection;Nanotubes;Water Pollutants, Chemical
摘要：
Fluorescence molecular imaging has attracted increasing attention due to its various advantages. Lots of fluorophores have been developed to meet various molecular imaging needs. However, it is still inconvenient due to the lack of excellent fluorophores with an optically tunable group for biological molecular imaging. Here a new platform of a versatile long wavelength fluorophore with an optically tunable hydroxyl group was successfully developed by regulating molecular planarity and the twisted intramolecular charge transfer effect with a protected and deprotected hydroxyl group approach via "step by step" modifying strategy. As an excellent representative of this new type of fluorophore, LDOH-4 possesses good chemical and optical properties and shows a potential application prospect. As a proof-of-concept, a nitroreductase-activated TP fluorescent probe LDO-NTR was designed, which not only sensitively recognizes NTR with more than 310-fold response signal enhancement in vitro but also tracks NTR in a hypoxia tumor mouse model in vivo by using two-photon imaging. It is hopeful that the long wavelength fluorophore with the optically tunable hydroxyl group can serve as a useful platform to extend capable detection tools in biological chemistry and biomedical applications.
作者机构：
[Zheng, Jing; Zhu, Cong; Chen, Shiya] Hunan Univ, Coll Chem & Chem Engn, State Key Lab Chemo Biosensing & Chemometr, Changsha 410082, Hunan, Peoples R China.;[Huang, Fujian] China Univ Geosci, Fac Mat Sci & Chem, Minist Educ, Engn Res Ctr Nanogeomat, Wuhan 430074, Hubei, Peoples R China.;[Yang, Ronghua] Changsha Univ Sci & Technol, Sch Chem & Biol Engn, Changsha 410076, Hunan, Peoples R China.;[Yang, Jinfeng] Cent S Univ, Hunan Canc Hosp, Affiliated Canc Hosp, Xiangya Sch Med, Changsha 410083, Hunan, Peoples R China.
通讯机构：
[Zheng, Jing] H;[Huang, Fujian] C;Hunan Univ, Coll Chem & Chem Engn, State Key Lab Chemo Biosensing & Chemometr, Changsha 410082, Hunan, Peoples R China.;China Univ Geosci, Fac Mat Sci & Chem, Minist Educ, Engn Res Ctr Nanogeomat, Wuhan 430074, Hubei, Peoples R China.
摘要：
A new triplex-functionalized DNA tetrahedral nanoprobe is proposed herein for monitoring pH and messenger RNA (mRNA) in living cells. Different from traditional DNA tetrahedron-based nanoprobes, DNA triplex was employed to serve as important conformational conversion elements. Inspired by the low extracellular pH in tumor cells, the mRNA-targeted H1 and H2 were stably assembled on the extended short hairpin probes of DNA tetrahedron via Hoogsteen bonding to form DNA triplex. Due to the high intracellular pH and presence of target mRNA, hybridization chain reaction (HCR) was triggered between H1 and H2 which were released from the dissociation of DNA triplex, and the generated long double-stranded DNA activated a Foster resonance energy transfer (FRET) signal indicating target mRNA expression even at very low contents. By combining the distinguishing feature of DNA triplex structure (pH-responsive) and HCR (signal amplification), sensitive imaging of intracellular pH and tumor-related mRNA can be realized. As a further application, dynamic imaging of intracellular pH and mRNA during "mitochondria-dependent" pathway apoptosis was successfully achieved in human breast cancer cells, which indicated huge potential of our proposed nanoprobe in early diagnosis and treatment of diseases.
摘要：
We report here a two-photon nanoprobe for the detection of RNase H activity in living cells and ex vivo tissues by combining a two-photon dye with a spherical nucleic acid (SNA) featuring a DNA/RNA duplex corona and a gold nanoparticle core.
