20 research outputs found

    Plasmon-Assisted Enhancement of the Ultraweak Chemiluminescence Using Cu/Ni Metal Nanoparticles

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    Cu/Ni nanoparticles (NPs) with stable fluorescence and excellent water dispersion were synthesized through a facile aqueous solution method with a similar Kirkendall effect. Ultraweak chemiluminescence (CL) from the oxidation reaction between sodium hydrogen carbonate (NaHCO<sub>3</sub>) and hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) in neutral medium was significantly enhanced by 60 ± 5 nm Cu/Ni NP with a copper and nickel molar ratio of 1:2. The enhancement of the time-dependent CL was dependent on the composition of the NP and the order of reagent addition. On the basis of studies of CL emission spectra, electron spin resonance spectra, UV–vis absorption, and fluorescence spectra, a mechanism of plasmon-assisted metal catalytic effect for this metal NP (MNP)-enhanced CL was proposed. The surface plasmons of MNP can obtain energy from chemical reaction, forming the activated MNP (MNP*), which was coupled to ·OH radical to produce the new adduct ·OH-MNP*. The ·OH-MNP* can accelerate the reaction rate of HCO<sub>3</sub><sup>–</sup> for the generation of emitter intermediate (CO<sub>2</sub>)<sub>2</sub>*, which can lead the enhanced CL for the overall reaction

    Determination of Ammonia in Water Based on Chemiluminescence Resonance Energy Transfer between Peroxymonocarbonate and Branched NaYF<sub>4</sub>:Yb<sup>3+</sup>/Er<sup>3+</sup> Nanoparticles

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    The ultraweak chemiluminescence (CL) from the reaction of hydrogen peroxide and carbonate is strongly enhanced by the branched NaYF<sub>4</sub>:Yb<sup>3+</sup>/Er<sup>3+</sup> nanoparticle (NP) in the presence of aqueous ammonia. It was explained that ammonia catalyzes the decomposition of peroxymonocarbonate, which is the product of hydrogen peroxide mixing with bicarbonate, making the formation of (CO<sub>2</sub>)<sub>2</sub>*, (O<sub>2</sub>)<sub>2</sub>*, and <sup>1</sup>O<sub>2</sub>. The excitation energy, carried by these emitter intermediates, can be transferred to NaYF<sub>4</sub>:Yb<sup>3+</sup>/Er<sup>3+</sup> NP. The CL intensity is directly proportional to the concentration of ammonia present in the solution. A flow-injection CL system with high sensitivity, selectivity, and reproducibility is proposed for the determination of aqueous ammonia. The proposed method exhibited advantages in a larger linear range from 0.5 μmol L<sup>–1</sup> to 50 μmol L<sup>–1</sup> and a lower detection limit of 1.1 × 10<sup>–8</sup> mol L<sup>–1</sup> (S/N = 3). This method has been successfully applied to the evaluation of ammonia in water samples with recoveries from 95% to 108%. The relative standard deviations are 1.8% and 4.1% for intra-assay and inter-assay precision, respectively

    Physicochemical Characterization of MF<sub><i>m</i></sub><sup>–</sup>‑Based Ammonium Ionic Liquids

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    A series of ammonium-based ionic liquids (ILs), which share a homologous series of cations (CH<sub>3</sub>CH<sub>2</sub>)<sub>3</sub>N<sup>+</sup>(C<sub><i>n</i></sub>H<sub>2<i>n</i>+1</sub>) with <i>n</i> = 2, 4, 6, 8 and the anions with either BF<sub>4</sub><sup>–</sup>, PF<sub>6</sub><sup>–</sup>, or SbF<sub>6</sub><sup>–</sup>, was synthesized. Their structures were confirmed by <sup>1</sup>H and <sup>13</sup>C NMR, ESI-MS, and elemental analysis. Meanwhile, the content of impurity (e.g., water and bromide ions) was also determined using Karl Fischer titrator and ion chromatography. The thermal properties of the ILs were determined by TGA and DSC. Five of the investigated ILs have been shown to have a low melting point (< 100 °C): <i>N</i>,<i>N</i>,<i>N</i>,<i>N</i>-tetraethylammonium tetrafluoroborate, [N<sub>2222</sub>]­BF<sub>4</sub>, <i>N</i>,<i>N</i>,<i>N</i>,<i>N</i>-tetraethylammonium hexafluorophosphate, [N<sub>2222</sub>]­PF<sub>6</sub>, <i>N</i>,<i>N</i>,<i>N</i>-triethylhexylammonium tetrafluoroborate, [N<sub>2226</sub>]­BF<sub>4</sub>, <i>N</i>,<i>N</i>,<i>N</i>-triethyloctylammonium hexafluorophosphate, [N<sub>2228</sub>]­PF<sub>6</sub> and <i>N</i>,<i>N</i>,<i>N</i>-triethyloctylammonium hexafluoroantimonate, [N<sub>2228</sub>]­SbF<sub>6</sub>. Densities, refractive indices, and miscibility of these 12 ILs were well studied systematically. Moreover, from the analysis of the structure–property relationship, the role of the alkyl chain length of the cation on these physical properties of the ILs has been assessed, and the influence of the nature of the anions on these experimental data of the ILs has been discussed. The studies may provide valuable contributions for the design and study of ILs

    Evaluation of the Absorption of Methotrexate on Cells and Its Cytotoxicity Assay by Using an Integrated Microfluidic Device Coupled to a Mass Spectrometer

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    An integrated microfluidic device was developed for high-throughput drug screening with an online electrospray ionization quadrupole time-of-flight mass spectrometer (ESI-Q-TOF MS). The multiple gradient generator followed by an array of microscale cell culture chambers and on-chip solid-phase extraction (SPE) columns for sample pretreatment prior to mass analysis was integrated in the device which was fabricated in one single step. By using the combination system, the process for characterization of drug absorption and evaluation of cytotoxicity could be simultaneously realized. To validate the feasibility, the absorption of methotrexate and its effects on HepG2 and Caco-2 cells were investigated. With the increasing concentration of drugs, the percentage of apoptotic cells appeared in a dose-dependent fashion. By comparison with the results obtained from ESI-Q-TOF MS analysis and cytotoxicity assay, we found that higher intracellular drug concentration resulted in increased cell cytotoxicity. The technique presented herein provides an easy protocol to screen drugs rapidly with low drug consumption, high throughput, and high sensitivity

    Cell Signaling Analysis by Mass Spectrometry under Coculture Conditions on an Integrated Microfluidic Device

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    A microfluidic device was integrated in a controlled coculture system, in which the secreted proteins were qualitatively and semiquantitatively determined by a directly coupled mass spectrometer. PC12 cells and GH3 cells were cocultured under various conditions as a model of the regulation of the organism by the nervous system. A micro-solid phase extraction (SPE) column was integrated in order to remove salts from the cells secretion prior to mass spectrometry detection. A three layer polydimethylsiloxane (PDMS) microfluidic device was fabricated to integrate valves for avoiding contamination between the cells coculture zone and the pretreatment zone. Electrospray ionization (ESI)-quadrupole (Q)-time of flight (TOF)-mass spectrometry was employed to realize highly sensitive qualitative analysis and to implement semiquantitative analysis. Furthermore, cell migrations under various coculture conditions were observed and discussed. The inhibition on growth hormone secretion from GH3 cells by dopamine released from PC12 cells was investigated and demonstrated. Thus, the developed platform provides a useful tool on cell to cell signaling studies for disease monitoring and drug delivery control

    Aggregation-Induced Structure Transition of Protein-Stabilized Zinc/Copper Nanoclusters for Amplified Chemiluminescence

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    A stable, water-soluble fluorescent Zn/Cu nanocluster (NC) capped with a model protein, bovine serum albumin (BSA), was synthesized and applied to the reaction of hydrogen peroxide and sodium hydrogen carbonate. A significantly amplified chemiluminescence (CL) from the accelerated decomposition of peroxymonocarbonate (HCO<sub>4</sub><sup>–</sup>) by the nanosluster was observed. The CL reaction led to a structure change of BSA and aggregation of Zn/Cu NCs. In the presence of H<sub>2</sub>O<sub>2</sub>, Zn/Cu–S bonding between BSA scaffolds and the encapsulated Zn/Cu@BSA NC was oxidized to form a disulfide product. Zn/Cu@BSA NCs were prone to aggregate to form larger nanoparticles without the protection of scaffolds. It is revealed that the strong CL emission was initiated from the catalysis of Zn/Cu@BSA NC and the surface plasmon coupling of the formed Zn/Cu nanoparticles in a single chemical reaction. This amplified CL was successfully exploited for selective sensing of hydrogen peroxide in environmental samples

    Iron-Catalyzed Diastereoselective Synthesis of Unnatural Chiral Amino Acid Derivatives

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    An iron-catalyzed diastereoselective synthesis of unnatural chiral (<i>S</i>)-α-amino acids with γ-quaternary carbon centers has been developed. The protocol uses inexpensive iron salt as the catalyst, readily available 2-phthaloyl acrylamide and alkenes as the starting materials, and phenylsilane as the reductant, and the reactions were performed well in mixed solvent of 1,2-dichloroethane and ethylene glycol at room temperature. The method shows some advantages including simple and wide substrates, mild conditions, high diastereoselectivity, and easy workup procedures

    Strategy for Signaling Molecule Detection by Using an Integrated Microfluidic Device Coupled with Mass Spectrometry to Study Cell-to-Cell Communication

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    Cell-to-cell communication is a very important physiological behavior in life entity, and most of human behaviors are related to it. Although cell-to-cell communications are attracting much attention and financial support, rare methods have been successfully developed for in vitro cell-to-cell communication study. In this work, we developed a novel method for cell-to-cell communication study on an integrated microdevice, and signaling molecule and metabolites were online-detected by an electrospray ionization-quadrupole-time-of-flight-mass spectrometer (ESI-Q-TOF-MS) after on-chip solid-phase extraction. Moreover, we presented a “Surface Tension Plug” on a microchip to control cell-to-cell communication. The microdevice consists of three functional sections: cell coculture channel, targets pretreatment, and targets detection sections. To verify the feasibility of cell-to-cell communications on the integrated microdevice, we studied the communication between the 293 and the L-02 cells. Epinephrine and glucose were successfully detected using an ESI-Q-TOF-MS with short analysis time (<10 min). The results demonstrated that the developed microfluidic device is a potentially useful tool for high throughput cell-to-cell communication study

    Chemiluminescence Character of ZnS Quantum Dots with Bisulphite-Hydrogen Peroxide System in Acidic Medium

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    In this work, ZnS quantum dots (QDs) capped with mercaptopropanoic acid were applied to the hydrogen peroxide-hydrogen sulfite chemiluminescence (CL) system. The CL intensity of the system was significantly enhanced by ZnS QDs in an acidic medium. The reactive oxygen species like superoxide ion (<sup>•</sup>O<sub>2</sub><sup>–</sup>), sulfite (<sup>•</sup>SO<sub>3</sub><sup>–</sup>), sulfate (<sup>•</sup>SO<sub>4</sub><sup>–</sup>), and hydroxyl (<sup>•</sup>OH) radicals were generated in the CL reaction. It is of worth to know that the order of addition of reagents sturdily influences CL intensity, indicating different free radical generation in response to the different orders. Interestingly, the addition of water to an optimum concentration ensued a further increase in CL signal, which may be due to hydrolysis reaction at higher concentration of NaHSO<sub>3</sub>. The enhanced CL was induced by excited ZnS QDs, which could be produced from the combination of hole (QDs (h<sup>+</sup>)) and electron (QDs (e<sup>–</sup>)) injected QDs as well as by chemical resonance energy transfer from <sup>1</sup>O<sub>2</sub> and SO<sub>2</sub>* to ZnS QDs. Four emitters such as <sup>1</sup>O<sub>2</sub>, (O<sub>2</sub>)<sub>2</sub>*, SO<sub>2</sub>*, and ZnS QDs* were detected in the CL system. Mechanistic investigation indicated that QDs acted as a catalyst, first decomposing H<sub>2</sub>O<sub>2</sub> to generate free radicals and second prompting CL by energy transfer and electron-transfer annihilation effects. Distinct from most QDs CL reactions which are classically attained in basic conditions, this system operates in an acidic medium. This may intrigue an avenue for investigating the CL property of QDs in an acidic medium and promote its application in various fields

    Shear Stress-Enhanced Internalization of Cell Membrane Proteins Indicated by a Hairpin-Type DNA Probe

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    Shear stress is an important mechanical stimulus that plays a critical role in modulating cell functions. In this study, we investigated the regulating effects of shear stress on the internalization of cell membrane proteins in a microfluidic chip. A hairpin-type DNA probe was developed and indiscriminately anchored to the cell surface, acting as an indicator for the membrane proteins. When cells were exposed to shear stress generated from fluid cell medium containing external proteins, strong fluorescence was emanated from intracellular regions. With intensive investigation, results revealed that shear stress could enhance the specific cell endocytosis pathway and promote membrane protein internalization. This process was indicated by the enhanced intracellular fluorescence, generated from the internalized and mitochondria accumulated DNA probes. This study not only uncovered new cellular mechanotransduction mechanisms but also provided a versatile method that enabled in situ and dynamic indication of cell responses to mechanical stimuli
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