11 research outputs found

    Electrocatalytic Efficiency Analysis of Catechol Molecules for NADH Oxidation during Nanoparticle Collision

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    Electrocatalysis of molecules is a hot research topic in biological and energy-related chemistry. Here, we develop a new system to study the electrocatalytic efficiency of a single catechol molecule for NADH oxidation by single functionalized nanoparticle collision at ultramicroelectrodes (UMEs). The proposed system is composed of gold nanoparticles (AuNPs) functionalized with catechol molecules and a carbon-fiber ultramicroelectrode. In the absence of NADH, when a functionalized AuNP collides with an UME at a suitable voltage, a small current spike is generated due to the oxidation of catechol molecules modified on the surface of AuNP. In the presence of NADH, the current spike is significantly amplified by the combined effects of the oxidation and electrocatalysis for NADH of catechol molecules. By analyzing the variations of the average peak charges and durations without or with NADH, we calculate that around five thousands NADH molecules could be catalyzed per second by a single catechol molecule, suggesting the successful establishment of this novel catalytic system. Thus, the proposed strategy could be used as a promising platform for research of other molecular electrocatalytic systems

    Highly Selective Detection of Carbon Monoxide in Living Cells by Palladacycle Carbonylation-Based Surface Enhanced Raman Spectroscopy Nanosensors

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    A novel nanosensor was explored for the highly selective detection of intracellular carbon monoxide (CO) by surface enhanced Raman spectroscopy (SERS) on the basis of palladacycle carbonylation. By assembling new synthesized palladacycles (PC) on the surface of gold nanoparticles (AuNPs), SERS nanosensors (AuNP/PC) were prepared with good SERS activity and reactivity with CO. When the AuNP/PC nanosensors were incubated with a CO-containing system, carbonylation of the PC assembled on AuNPs was initiated, and the corresponding SERS spectra of AuNP/PC changed significantly, which allowed the carbonylation reaction to be directly observed <i>in situ</i>. Upon SERS observation of CO-dependent carbonylation, this SERS nanosensor was used for the detection of CO under physiological conditions. Moreover, benefiting from the specificity of the reaction coupled with the fingerprinting feature of SERS, the developed nanosensor demonstrated high selectivity over other biologically relevant species. <i>In vivo</i> studies further indicated that CO in normal human liver cells and HeLa cells at concentrations as low as 0.5 ÎŒM were successfully detected with the proposed SERS strategy, demonstrating its great promise for the analytical requirements in studies of physiopathological events involved with CO

    Electrocatalytic Oxidation of Tris(2-carboxyethyl)phosphine at Pyrroloquinoline Quinone Modified Carbon Nanotube through Single Nanoparticle Collision

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    Inspired by the addition-elimination catalytic mechanism of natural pyrroloquinoline quinone (PQQ) containing proteins, PQQ-modified hybrid nanomaterials have been increasingly developed recently as biomimetic heterogeneous electrocatalysts. However, up until now, no existing electrochemical approach was able to assess the intrinsic catalytic activity of PQQ sites, impeding the design of efficient PQQ-based electrocatalysts. Herein, in this work, we introduced a new method to calculate the turnover frequency (TOF) of any individual PQQ functional group for electrocatalytic oxidation of tris­(2-carboxyethyl)­phosphine (TCEP), through the study of single PQQ-decorated carbon nanotube (CNT) collisions at a carbon fiber ultramicroelectrode by chronoamperometry. The core advantage of this approach is being able to resolve the number of PQQ catalytic sites grafted on each individual CNT, so that the charge of any CNT collision event can be accurately translated into the intrinsic activity of the respective PQQ functional groups. The resulting collision-induced current responses clearly showed that the functionalization of CNTs with PQQ could indeed enhance its catalytic performance by 3 times, reaching a TOF value of 133 s<sup>–1</sup> at 1.0 V vs Ag/AgCl. Such a single CNT collision technique, which is proposed for the first time in this work, can open up a new avenue for studying the intrinsic (electro)­catalytic performance at a molecular level

    Individual Modified Carbon Nanotube Collision for Electrocatalytic Oxidation of Hydrazine in Aqueous Solution

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    Collision at a single molecule level was achieved based on the nanoimpact of an individual pyrroloquinoline quinone (PQQ) modified multiwalled carbon nanotube (MWCNT) at the carbon fiber ultramicroelectrode (C UME). Electrocatalytic amplification of the current responses was observed when the PQQ-modified MWCNT collided with C UME in the presence of hydrazine (N<sub>2</sub>H<sub>4</sub>) in a Tris-HCl buffer solution, which was also supported by the conventional cyclic voltammetry and chronoamperometry techniques. The enhanced catalytic oxidation of N<sub>2</sub>H<sub>4</sub> was due to the “addition-elimination” redox cycling mechanism of PQQ/PQQH<sub>2</sub>, where the oxidation of N<sub>2</sub>H<sub>4</sub> occurred together with the reduction of PQQ under an external bias, and the formed PQQH<sub>2</sub> intermediate would be reoxidized back to PQQ simultaneously. The average collision current, duration, and charge for PQQ-modified MWCNT at 1.0 V vs Ag/AgCl were 105 pA, 0.45 ms, and 49 fC, respectively. As a result, the turnover frequency of electrocatalytic oxidation of N<sub>2</sub>H<sub>4</sub> by PQQ was calculated to be 54 s<sup>–1</sup>. In this regard, the proposed individual carbon nanotube collision method can not only serve as a promising sensing technique to detect biochemical species, but more importantly provide a robust approach to determine the intrinsic catalytic activity as well

    Effect of IR-A overexpression on downstream signaling pathways.

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    <p>A. Western blot analysis of IR protein expression and expression of downstream signaling proteins in RL95-2-CON, RL95-2–NC and RL95-2–IR-A cells. B. IR protein expression in RL95-2–IR-A cells is significantly higher than that in RL95-2–CON and RL95-2–NC cells. C. The relative expression of phospho-Akt is signiïŹcantly increased and the relative expression of phosphorylated ERK1/2 reduced in RL95-2–IR-A cells than controls. *, #, <i>P</i> < 0.05 vs. control.</p

    IR-A expression in endometrial carcinoma cell lines.

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    <p>A. Expression of IR-A (444 bp), IR–B (480 bp), IGF-2 (214 bp) and GAPDH (226 bp) mRNA in endometrial carcinoma cell lines was measured by RT-PCR. The results indicates that two transcript isoforms of insulin receptors (IR-A and IR–B) and IGF-2 were co-expressed in HEC-1-A, Ishikawa, KLE and RL95-2–CON cells. RL95-2–CON has a much higher ratio of IR–B expressed than IR-A. B. Real-time RT-PCR indicates the relative levels of IR-A and total IR mRNA in endometrial carcinoma cell lines, normalized to GAPDH. C.The ratio of IR-A/ IR in endometrial cancer cell lines from real-time RT-PCR results. D. ELISA quantitation of IGF-2 protein secreted by RL95-2–CON, RL95-2–IR-A, KLE, HEC-1-A and Ishikawa cells.</p

    Expression of IR-A/ IR–B in endometrial carcinoma tissues and control normal endometrium tissues.

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    <p>A. Representative examples of the endometrial carcinoma tissues (total 103cases). Lane M shown the DNA marker and Lanes T1–T19 correspond to 19 separate endometrial carcinoma patients B. Representative examples of control normal endometrium tissues(total 60 cases). Lanes N1–N25 correspond to 25 separate patients with normal endometrium.</p

    IR-A overexpression increases cell proliferation rate.

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    <p>A. Proliferation of RL95-2–IR-A, RL95-2–CON and RL95-2–NC cells was measured over a 7-day period (plate 2000 cells/well as starting cells) B. Proliferation of the three cells was measured after 72 hours (plate 2000, 5000, 10000, 20000 cells/well as starting cells). 6 replicate wells were included per sample and the data points were present as means±SD. *, <i>P</i> < 0.05 vs. control.</p

    Tumorigenicity of the RL95-2–IR-A, RL95-2–CON and RL95-2–NC cells in a xenograft model.

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    <p>A. Photographs of the inoculated BALB/c nude mice five weeks after inoculation, showing the tumor size. B. RL95-2–IR-A, RL95-2–CON and RL95-2–NC cells were injected groups of five mice and tumor volumes were measured using calipers every week after the inoculation. C. Five weeks after inoculation, tumors were excised, fixed, and stained by hematoxylin and eosin (H&E; 400× magnification). *, <i>P</i> < 0.05 vs. control.</p

    PI3K inhibition reverses the effects of IR-A overexpression.

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    <p>A. Western blot analysis of phospho-Akt and total Akt levels 48 h after treatment with 5, 10, 20 and 40 ”M of LY294002. B. Growth curves of RL95-2–IR-A cells following treatment with 20 ”M LY294002 and without. C. Flow cytometry analysis indicating the proportion of RL95-2–IR-A cells containing S phase DNA at 48 h after treatment with 20 ”M LY294002. D. Flow cytometry analysis indicating the percentage of apoptotic cells in RL95-2–IR-A cells at 48 h after treatment with 20 ”M LY294002. *, <i>P</i> < 0.05 vs. control.</p
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