Sensitive detection of choline and nicotine in real samples by switching upconversion luminescence.

Nicotine (3-(1-methyl-2-pyrrolidinyl)pyridine) is one of the most common addictive substances, causing the trace detection of nicotine to be very necessary. Herein, we designed and prepared a functionalized nanocomposite CS-PAA (NaYF4:19.5%Yb,0.5%Tm@NaYF4-PAA) using a simple method. The nicotine concentration was quantitatively detected through the inhibition of choline oxidase activity by nicotine and the luminescence intensity of CS-PAA being quenched by Fe3+. The mechanism of Fe3+ quenching CS-PAA emission was inferred by luminescence lifetime and UV-vis absorption spectra characterization. During the nicotine detection, both excitation (980 nm) and emission (802 nm) wavelengths of CS-PAA enable the avoidance of the interference of background fluorescence in complicated food objects, thus providing high selectivity and sensitivity with a linear range of 5-750 ng/mL and a limit of detection of 9.3 nM. The method exhibits an excellent recovery and relative standard deviation, indicating high accuracy and repeatability of the detection of nicotine.

Palladium-catalyzed Suzuki-Miyaura cross-coupling of carboxylic-phosphoric anhydrides via C-O bond cleavage.

A robust palladium-catalyzed Suzuki-Miyaura reaction of carboxylic-phosphoric anhydrides via highly selective C(O)-O bond cleavage under inorganic base-free conditions has been reported. Carboxylic-phosphoric anhydrides, generated through activating carboxylic acids using phosphates by esterification or direct dehydrogenative reaction with phosphites, have been employed as highly reactive electrophiles for Suzuki-Miyaura cross-coupling reactions. Broad substrate scope and excellent functional group tolerance have been demonstrated to be a general and practical approach for the synthesis of highly valuable ketones.

Optical Upconversion in Mononuclear Lanthanide Co-Crystal Assemblies.

In this work, we developed two kinds of co-crystal assemblies systems, consisting of discrete mononuclear Yb3+ and Er3+ and mononuclear Yb3+ and Pr3+, which can achieve Er3+ and Pr3+ upconversion luminescence, respectively, by Yb3+ sensitization under 980 nm excitation. The structure and composition of two co-crystal assemblies were determined by single crystal X-ray diffraction. By investigation of the series of two assemblies, respectively, it is found that the strongest upconversion luminescence is both obtained when the molar ratio of Yb3+ and Ln3+ (Ln=Er or Pr) is 1 : 1. The energy transfer mechanism of Er3+ assemblies is determined as energy transfer upconversion, while that of Pr3+ assemblies is determined as energy transfer upconversion and cooperative sensitization upconversion. This is the first example of Pr3+ upconversion luminescence at the molecular dimension at room temperature, which enriches the research in the field of upconversion luminescence with lanthanide complexes.

Anthraquinone-1,8-Derived (Pseudo-) Crown and Lariat Ethers:Design and Applications as Fluorescent and Chromogenic Ion (Pair) Sensors.

Cyclic polyamine/ethers embedded with anthraquinone moieties and functional pendants, are structural analogues of crown ethers and (oxo-) cyclams, and could be utilized as sensitive and selective chemosensors towards metal cations. Those pseudo- (similar but geometrically distinct) crown and lariat ethers show various cation-binding patterns and stoichiometry, being modulated by donor type, cavity size and pendants' chelating ability. The luminescent and chromogenic properties also differ a lot along with the derivation of the parental macrocycle. Methodological designing including synthesis and post-functionalization through nucleophilic substitution, Mannich condensation etc., as well as the sensing performance of those pseudo-crown and lariat ethers are summarized in this review, basing on the spectroscopic, voltammetric and X-ray crystallographic determinations. Anion effect in sensing cations is evaluated according to the ion-pair recognition theory. Those results shed some light on exemplifying the anions' role in bioinorganic systems including metalloenzymes.

Chemical constituents of Viscum coloratum (Kom.) Nakai and their cytotoxic activities.

A new diarylheptanoid, (1 R,2S,3S,5S)-2,3-dihydroxy-3',3''-dimethoxy-4'-de-O-methylcentrolobine (1) and a new bisabolane-type sesquiterpenoid, (1 R,7S)-1,12,13-trihydroxybisabola-3,10-diene (2), together with nineteen known compounds (3-21) were isolated from the EtOH extract of the stems and branches of Viscum coloratum (Kom.) Nakai. Their structures were elucidated by extensive analysis of 1 D and 2 D NMR spectra and from the HRESIMS. All the compounds were evaluated for their cytotoxic activity against eight human tumor cell lines.

Achieving stable Na metal cycling via polydopamine/multilayer graphene coating of a polypropylene separator.

Sodium metal batteries are considered one of the most promising low-cost high-energy-density electrochemical energy storage systems. However, the growth of unfavourable Na metal deposition and the limited cell cycle life hamper the application of this battery system at a large scale. Here, we propose the use of polypropylene separator coated with a composite material comprising polydopamine and multilayer graphene to tackle these issues. The oxygen- and nitrogen- containing moieties as well as the nano- and meso- porous network of the coating allow cycling of Na metal electrodes in symmetric cell configuration for over 2000 h with a stable 4 mV overpotential at 1 mA cm-2. When tested in full Na || Na3V2(PO4)3 coin cell, the coated separator enables the delivery of a stable capacity of about 100 mAh g-1 for 500 cycles (90% capacity retention) at a specific current of 235 mA g-1 and satisfactory rate capability performances (i.e., 75 mAh g-1 at 3.5 A g-1).

A carbon-coated spinel zinc cobaltate doped with manganese and nickel as a cathode material for aqueous zinc-ion batteries.

Here, a new amorphous material composed of carbon-coated zinc cobaltate doped with manganese and nickel ZNMC@C (ZnNi0.5Mn0.5CoO4@C) with a spinel structure is proposed as a cathode material for use in aqueous zinc-ion batteries. This cathode material exhibits a high charge/discharge capacity with an initial capacity of about 160 mA h g-1 and its capacity retention rate remains at 60% after 500 cycles at 0.2 A g-1, which is higher than that of some reported spinel cathode materials. This superior electrochemical performance can be ascribed to the synergistic effect of the co-doping of manganese and nickel, which produces reversible multivalence redox transition activity (Co4+/Co3+, Ni4+/Ni3+/Ni2+, and Mn4+/Mn3+) that facilitates the insertion and migration of zinc ions and the existence of an outer amorphous carbon coating that effectively inhibits the dissolution of the cathode structure and stabilizes the cathode structure. In addition, the cycling mechanism of ZNMC@C was analyzed in detail through electrochemical measurements of the different cycling stages, including the kinetic behavior based on cyclic voltammetry and electrochemical impedance spectroscopic analysis and the reaction mechanism from X-ray photoelectron spectroscopy, ex situ X-ray diffractometry and ex situ scanning electron microscopy analysis. These research results suggest that the ZNMC@C composite material could be a competitive cathode material for Abs (aqueous rechargeable batteries).

Composition and structural characterization of pectin in micropropagated and conventional plants of Premma puberula Pamp.

The metabolites produced by plants can be enhanced by plant tissue culture. In Premma puberula Pamp., the pectin content in leaves is 30 %-40 %, and it is widely used in the food industry and medicine. However, inefficient propagation has seriously restricted the utilization of pectin resources. Therefore, we established an efficient micropropagation technology for P. puberula through comparative analysis in mature leaves of regenerated and conventionally propagated plants. The results showed that the pectin composition of their leaves was similar in terms of galacturonic acid, monosaccharide composition, degree of esterification, functional groups, nuclear magnetic resonance spectrum and morphological characteristics. Furthermore, micropropagated plants had better hardness, gumminess and chewiness characteristics than conventionally propagated plants and were similar in emulsion stability, adhesiveness, springiness, cohesiveness and viscoelasticity. Therefore, micropropagation technology will provide an important guarantee for the industrial production of pectin from P. puberula. The technical essentials include callus induction, embryoid formation, and root induction, followed by acclimatization and transplanting.

Structures and Chromogenic Ion-Pair Recognition of a Catechol-Functionalized 1,8-Anthraquinone Macrocycle in Dimethyl Sulfoxide.

A lariat anthraquinone macrocycle functionalized with catechol (H2L) was synthesized via the Mannich reaction. The Mannich base H2L can be partially decomposed into L1·3H2O and HL1·NO3·2H2O in the presence of tetrabutylammonium hydroxide/Al(NO3)3·9H2O in dimethyl sulfoxide (DMSO). Free L1·3H2O is essentially coplanar, while protonated HL1·NO3·2H2O is highly distorted. Dark-green FeCl3·H2L·2H2O powder and Fe2(HL)2Cl4 crystal can be isolated from ethanol (C2H5OH) in high/low H2L concentration. Anthraquinone in H2L is essentially coplanar but distorted in Fe2(HL)2Cl4. The Fe(III) ion in Fe2(HL)2Cl4 adopts a less common five-coordination with three catecholate O and two Cl atoms in the dimer. The distortion of inbound C═O is much higher than that of outbound C═O in anthraquinone in all of these compounds. H2L responds to chlorides of Li+, Na+, K+, Cs+, Mg2+, Ca2+, Sr2+, Ba2+, Fe3+, Cu2+, Zn2+, and Al3+ in a DMSO solution, which can be observed by differential pulse voltammetry, UV-vis, and 1H NMR. All of these metal ions shift Ep of anthraquinone to positive, especially the second reduction peak of anthraquinone. Fe3+, Zn2+, and Al3+ change the reduction of catechol fundamentally. H2L (0.50 mM) shows a chromogenic response to FeCl3 and Fe(NO3)3 to form uncommon 2:1 and 3:2 (H2L/Fe) complexes, both peaking at 748 nm in DMSO. In the presence of 2 equiv of sodium hydroxide (NaOH), the 748 nm absorbance shifts to 777 nm, identical with Fe2(HL)2Cl4 in DMSO. Different from the fast reaction between H2L and FeCl3, Fe(NO3)3 reacts with H2L rather slowly in DMSO. Catechol can coordinate to FeCl3 without any deprotonation in C2H5OH and DMSO. H2L also shows a chromogenic response to fluorides and hydroxides, which peak at 670 and 684 nm, respectively, in DMSO. The binding ratio between H2L and F-/OH- is 1:2. In a higher concentration of hydroxides, a 684 nm greenish-blue 1:2 complex forms immediately, which gradually transforms to a red complex and peaks at ∼530 nm in minutes at room temperature. No color change can be observed in an C2H5OH solution in the presence of OH-.

Synergy of strains that accelerate biodegradation of pyridine and quinoline.

Three bacterial strains were isolated from activated sludge acclimated to biodegrade pyridine and quinoline simultaneously. The strains were identified as Bacillus tropicus, Bacillus aquimaris, and Rhodococcus ruber. When the isolated bacteria were used for pyridine and quinoline biodegradation in separate or combined modes, R. ruber had much faster kinetics, and combining R. ruber with one or both of the Bacillus strains increased further the biodegradation kinetics. For example, the time needed for complete biodegradation of 1 mM quinoline and pyridine decreased to 20 h and 6 h, respectively, with the three strains combined, compared to 26 h and 7 h with R. ruber alone. Whereas quinoline was completely mineralized by all three strains, 10-14% of the pyridine persisted as a dead-end product, 2-hydroxypyridine (2HP). The acclimated sludge from which the three bacterial species were isolated was able to transform 2HP, and adding the bacterial strains (especially R. ruber) to the acclimated sludge accelerated the rate of 2HP removal and mineralization through a form of synergy.

Knockdown of phosphatase and tensin homolog (PTEN) inhibits fatty acid oxidation and reduces very low density lipoprotein assembly and secretion in calf hepatocytes.

Dairy cows with fatty liver exhibit hepatic lipid accumulation and disturbances in fatty acid oxidation and lipid transport. Phosphatase and tensin homolog (PTEN), a lipid phosphatase, regulates intrahepatic fatty acid oxidation and lipid transport in mice. Whether PTEN play a role in fatty acid oxidation and very low density lipoprotein (VLDL) assembly in calf hepatocytes are unknown. Hepatocytes isolated from 3 healthy female Holstein calves (1 d old, 30-40 kg) were infected with empty adenovirus with green fluorescent protein for 48 h (Ad-GFP group) or infected with PTEN knockdown adenovirus for 48 h (Ad-shPTEN group), or cultured in RPMI-1640 without Ad-shPTEN or Ad-GFP (control group). Compared with the Ad-GFP group, PTEN knockdown decreased mRNA and protein abundance and the activity of fatty acid oxidation-related molecules, including acyl-coA synthetase long-chain 1, carnitine palmitoyltransferase 1, carnitine palmitoyltransferase 2, and 3-hydroxy acyl-coA dehydrogenase. Furthermore, PTEN knockdown decreased mRNA and protein abundance of VLDL assembly-related molecules, including apolipoprotein B100, apolipoprotein E, microsomal triglyceride transfer protein, and low density lipoprotein receptor. Importantly, PTEN knockdown promoted triglyceride accumulation in hepatocytes and reduced the VLDL content in culture medium. A subsequent study was conducted on the following 4 groups: cells infected with Ad-GFP for 48 h and then treated with 2% BSA for another 24 h (Ad-GFP + BSA); cells infected with Ad-GFP for 48 h and then treated with 1.2 mM free fatty acids (FFA) and 2% BSA for another 24 h (Ad-GFP + 1.2 mM FFA); cells infected with Ad-shPTEN for 48 h and then treated with 2% BSA for another 24 h (Ad-shPTEN + BSA); cells infected with Ad-shPTEN for 48 h and then treated with 1.2 mM FFA and 2% BSA for another 24 h (Ad-shPTEN + 1.2 mM FFA). Compared with Ad-GFP + BSA, the abundances of PTEN and of fatty acid oxidation- and VLDL assembly-related proteins were lower in the Ad-GFP + 1.2 mM FFA group. Importantly, PTEN knockdown heightened the increase in triglyceride accumulation of hepatocytes and the decrease in VLDL content in culture medium induced by FFA. Overall, these in vitro data indicate that FFA inhibits PTEN expression, leading to triglyceride accumulation and the inhibition of VLDL assembly in calf hepatocytes. These findings suggest that PTEN may be a potential therapeutic target for FFA-induced hepatic steatosis in dairy cows.

ß-Lactoglobulin amyloid fibril-templated gold nanoclusters for cellular multicolor fluorescence imaging and colorimetric blood glucose assay.

ß-Lactoglobulin amyloid fibril (BLGF)-capped gold nanoclusters (Au NCs) with red, green and blue emissions were fabricated via pH-dependent reduction strategy. The BLGF-Au NCs exhibited 3.2 times enhancement of fluorescence (λex = 500 nm, λem = 684 nm), a significant 42 nm red shift, a 11.57% quantum yield and a 1.4 µs decay time compared with native ß-lactoglobulin (BLG)-stabilized Au NCs. Meanwhile, the multicolor Au NCs were employed for cell imaging via incubation with A549 cells for 14 h. According to the Michaelis-Menten equation, the kinetic parameters of the BLGF-Au NCs showed a lower Km value (66 µmol L-1) for 3,3,5,5-tetramethylbenzidine (TMB) and a higher vmax (3.74 × 10-8 M s-1) for H2O2, which are comparable with other artificial nanoenzymes and natural peroxidases. Based on the highly intrinsic peroxidase-like activity of the BLGF-Au NCs, a colorimetric method was developed for glucose determination with a detection limit of 1.5 µmol L-1 by determining the variation of the absorption at 652 nm, ranging from 5 to 100 µmol L-1. In addition, the glucose assay method also revealed a 101.02 to 104.16% recovery in a real human serum sample.

Sensitive and reversible perylene derivative-based fluorescent probe for acetylcholinesterase activity monitoring and its inhibitor.

A reversible fluorescence probe for acetylcholinesterase activity detection was developed based on water soluble perylene derivative, N,N'-di(2-aspartic acid)-perylene-3,4,9,10-tetracarboxylic diimide (PASP). Based on the photo-induced electron transfer (PET), PASP fluorescence in aqueous is quenched after combining with copper ions (Cu2+). Acetylcholinesterase (AChE) is well known to catalyze the hydrolysis of acetylcholine (ATCh) to produce thiocholine, whose affinity is strong enough to capture Cu2+ by thiol (-SH) group from the complex PASP-Cu, resulting in the fluorescence signal of PASP recovers up to 90%. This optical switch is highly sensitive depended on the coordination and dissociation between PASP and Cu2+. We proposed its application for AChE activity detection, as well as its inhibitor screening. According to the change of fluorescence intensity, quantifying the detection limit of AChE was 1.78 mU·mL-1. Classical inhibitors, tacrine and organophosphate pesticide diazinon, were further evaluated for drug screening. The IC50 value of tacrine was calculated to be 0.43 µM, and the detection limit of diazinon was 0.22 µM. Both of these performances were much better than previous results, revealing our probe is sensitive and reversible for screening applications.

Chiral Self-Assembly of Porphyrins Induced by Chiral Carbon Dots.

Chirality plays a key role in many fields ranging from life to natural sciences. For a long time, chiral materials have been developed and used to interact with chiral environments. In recent years, fluorescent carbon dots (CDots) are a new class of carbon nanomaterials exhibit excellent optical properties, good biocompatibility, excellent water solubility, and low cost. However, chirality transfer between semiconductor CDots and organics remains a challenge. Herein, a facile one-step hydrothermal method was used to synthesize chiral CDs from cysteine (cys). The obtained chiral CDots can act as chiral templates to induce porphyrins to form chiral supramolecular assemblies. The successful transmission of chiral information provides more options for the development of various chiral composite materials and the preservation of chiral information in the future.

Right-/left-handed helical G-quartet nanostructures with full-color and energy transfer circularly polarized luminescence.

Right (R)- and left (L)-handed helical G-quartet nanostructures were synthesized for the first time simultaneously via the self-assembly of 5'-guanosine monophosphate (GMP), the helical handedness of which is well regulated by metal ions. These g-nanostructures were further applied as circularly polarized luminescence (CPL) templates to realize full-color R-/L-CPL and Förster resonance energy transfer CPL. The glum value reached 10-2, indicating their excellent template function for CPL materials design and application.

Label-free iodide detection using functionalized carbon nanodots as fluorescent probes.

A label-free fluorescent nanoprobe for iodide ion (I-) detection was developed based on the direct fluorescence quenching of spermine-functionalized carbon dots (SC-dots), whether in complex biological fluids or living cells. The positively charged SC-dots were fabricated via one-step microwave synthesis and exhibited excellent optical properties. Due to the strong quenching ability of I-, SC-dots were utilized for I- detection with high sensitivity and excellent selectivity, which offered a relatively low detection limit of 0.18 µM. This strategy was also successfully applied for I- detections in human serum and HeLa cells. The detection process is facile, highly sensitive and selective, providing a new insight into the potential applications of SC-dots for anion nanoprobe designs in clinical diagnosis and other biologically related areas. Graphical abstract.

Fibrinogen-templated gold nanoclusters for fluorometric determination of cysteine and mercury(II).

Gold nanoclusters (Au NCs) using fibrinogen (FBG) protein as template are fabricated via one-pot reduction strategy, and applied for fluorometric detections of cysteine (Cys) and mercury(II). The modified FBG-Au NCs exhibit red fluorescence, with excitation/emission maxima at 360/620 nm, a 7% quantum yield, and a 2.2 µs decay time. The fluorescence of the nanoprobe is quenched by Cys and Hg(II). Cys can be determined by fluorometry in the 0.01 to 150 µmol L-1 concentration range and with a detection limit of 0.79 µmol L-1. Due to the oxidation of Hg(II), it can be detected in the 0.01 to 10 µmol L-1 concentration range. The properties of the FBG-Au NCs and the analytical performance are comparable with previously reported peptide/protein-templated Au NCs, supplying a promising candidate for Au NCs nanoprobes synthesis and applications. Graphical abstractSchematic representation of the preparation of gold nanoclusters (Au NCs) using fibrinogen (FBG) as the template. The modified Au NCs were applied to the fluorometric detection of cysteine (Cys) and mercury ion (Hg(II)).

DNA conformational polymorphism for biosensing applications.

In this mini review, we will briefly introduce the rapid development of DNA conformational polymorphism in biosensing field, including canonical DNA duplex, triplex, quadruplex, DNA origami, as well as more functionalized DNAs (aptamer, DNAzyme etc.). Various DNA structures are adopted to play important roles in sensor construction, through working as recognition receptor, signal reporter or linking staple for signal motifs, etc. We will mainly summarize their recent developments in DNA-based electrochemical and fluorescent sensors. For the electrochemical sensors, several types will be included, e.g. the amperometric, electrochemical impedance, electrochemiluminescence, as well as field-effect transistor sensors. For the fluorescent sensors, DNA is usually modified with fluorescent molecules or novel nanomaterials as report probes, excepting its core recognition function. Finally, general conclusion and future perspectives will be discussed for further developments.

Bis(2-pyridylmethyl)amine-functionalized alizarin: an efficient and simple colorimetric sensor for fluoride and a fluorescence turn-on sensor for Al3+ in an organic solution.

A complexone analog chemosensor, H2L, bearing chelating bis(2-pyridylmethyl) amine and alizarin groups was synthesized via the Mannich reaction. H2L chromically responds to OH-, F-, CH3COO-, and H2PO4- in DMF, CH3CN, and acetone, but not in CH3OH or H2O. The addition of F- ions to H2L selectively induces a significant and visible color change in acetonitrile and shifts both methylene proton signals upfield. H2L also exhibits visible responses to Mg2+, Sr2+, Ba2+, Tb3+, Cu2+, Co2+, Ni2+, Zn2+, Mn2+, Cd2+, and Fe3+ in solution. AlCl3 can form an Al : L = 2 : 3 complex that not only changes the color of the DMF solution, but also significantly increases its fluorescence intensity. The limit of fluorescence turn-on detection for AlCl3 in DMF is 2.7 × 10-8 M, which is an order higher than those of other anthraquinone sensors reported in the literature. NMR spectroscopy shows that hydroxyl is not deprotonated upon interacting with Al3+, but will be partially deprotonated in the presence of Zn2+. Contrary to the complexone, the H2L-Ce(iii) complex does not react chromically to F-. However, the H2L-NiCl2 complex responds chromically to F-, with higher sensitivity (LOD = 1.3 × 10-6 M F- in acetonitrile) than free H2L. The spectral changes in the presence of F- are similar to that of OH-; however, the spectrum shifts slightly to a longer wavelength and is more sensitive to both H2L and the H2L-NiCl2 complex. Moreover, 4% or less H2O in the solvent essentially has no influence on the F- sensitivity; however, high water content significantly decreases the F- sensitivity. The spectral changes of the Zn2+, Cu2+, Fe3+, Ce3+, and Ni2+ complexes in the presence of different NaOH concentrations were also investigated.