14 research outputs found

    Investigation of Silver Nanoparticle Induced Lipids Changes on a Single Cell Surface by Time-of-Flight Secondary Ion Mass Spectrometry

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    Lipids are the main component of the cell membrane. They not only provide structural support of cells but also directly participate in complex cellular metabolic processes. Lipid signaling is an important part of cell signaling. Evidence showed that abnormal cellular metabolism may induce lipids changes. Besides, owing to single cell heterogeneity, it is necessary to distinguish different behaviors of individual cells. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a sensitive surface analysis technique with high spatial resolution, which is useful in single cell surface analysis. Herein, we used ToF-SIMS to investigate silver nanoparticle induced lipids changes on the surface of single macrophage cells. Delayed extraction mode of ToF-SIMS was used to simultaneously obtain high mass resolution of mass spectra and high spatial resolution of single cell chemical imaging. Principle component analysis (PCA) results showed good agreement with the cytotoxicity assay results. Clear distinctions were observed between the cell groups treated with high or low dose of silver nanoparticles. The loadings plots revealed that the separation was mainly due to changes of cholesterol and diacylglycerol (DAG) as well as monoacylglycerol (MAG). Meanwhile, the chemical mapping of single cell components showed that cholesterol and DAG tend to migrate to the surrounding of the cells after high dose silver nanoparticles (Ag NPs) treatment. Our results demonstrated the feasibility of ToF-SIMS for characterizing the changes of the lipids on a single cell surface, providing a better understanding of the mechanism of cell–nanoparticle interactions at the molecular level

    Mussel-Inspired Polydopamine Functionalized Plasmonic Nanocomposites for Single-Particle Catalysis

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    Polydopamine functionalized plasmonic nanocomposites with well-distributed catalytically active small gold nanoislands around large gold core were fabricated without using any chemical reductant or surfactant. The optical properties, surface molecular structures, and ensemble catalytic activity of the gold nanocomposites were investigated by time-of-flight secondary ion mass spectrometry and UV–vis spectroscopy, respectively. Moreover, the considerable catalytic activity of the nanocomposites toward 4-nitrophenol reduction was real time monitored by dark-field spectroscopy techniques at the single-nanoparticle level avoiding averaging effects in bulk systems. According to the obtained plasmonic signals from individual nanocomposites, the electron charging and discharging rates for these nanocomposites during the catalytic process were calculated. Our results offer new insights into the design and synthesis of plasmonic nanocomposites for future catalytic applications as well as a further mechanistic understanding of the electron transfer during the catalytic process at the single-nanoparticle level

    Polydimethysiloxane Modified Silica Nanochannel Membrane for Hydrophobicity-Based Molecular Filtration and Detection

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    We report in this work the fabrication of ultrathin silica nanochannel membranes inhomogeneously modified by polydimethysiloxane (PDMS), designated as PDMS-SNM, for hydrophobicity-based molecular filtration and detection. The modification was accomplished by spatially selective evaporation of hydrophobic PDMS oligomers onto the top surface of the membrane and orifice of silica nanochannels. Thanks to this hydrophobic ultrathin layer and beneath ultrasmall channels (2–3 nm in diameter), only small hydrophobic molecules are able to transport through the PDMS-SNM, whereas hydrophilic and large ones are remarkably inhibited. We first employed this PDMS-SNM as the molecular sieving matrix for selective electrochemical detection of hydrophobic organophosphates (OPs) in milk samples without pretreatment. The PDMS-SNM modified electrode displayed an excellent analytical performance and antifouling/anti-interference ability. We also prepared the free-standing PDMS-SNM consisting of perforated channels, which could filtrate molecules based on their hydrophobicity with an excellent selectivity. As demonstrated, 2,4,6-trinitrotoluene and dopamine could be separated with a selectivity coefficient as high as 335. Moreover, because of the inhomogeneous nanochannel structure and ultrasmall thickness, a remarkably high flux of hydrophobic molecules across the PDMS-SNM was obtained, which was 3–4 orders of magnitude higher than that reported previously

    Image_1_Antibacterial Activity and Mechanism of Action of Aspidinol Against Multi-Drug-Resistant Methicillin-Resistant Staphylococcus aureus.TIF

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    <p>This study aimed at investigating the antibacterial activity of aspidinol, an extract from Dryopteris fragrans (L.) Schott, against methicillin-resistant Staphylococcus aureus (MRSA). MRSA isolates were treated with aspidinol to determine the differential expression of genes and associated pathways following the drug treatment. Aspidinol displayed significant anti-MRSA activity, both in vivo (minimum inhibitory concentration = 2 μg/mL) and in vitro, and achieved an antibacterial effect comparable to that of vancomycin. In the lethal septicemic mouse study, a dose of 50 mg/kg of either aspidinol or vancomycin provided significant protection from mortality. In the non-lethal septicemic mouse study, aspidinol and vancomycin produced a significant reduction in mean bacterial load in murine organs, including the spleen, lung, and liver. After treatment with aspidinol, we found through RNA-seq and RT-PCR experiments that the inhibition of the formation of ribosomes was the primary S. aureus cell-killing mechanism, and the inhibition of amino acid synthesis and the reduction of virulence factors might play a secondary role.</p

    Signal Amplification Cytosensor for Evaluation of Drug-Induced Cancer Cell Apoptosis

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    Apoptosis is involved in the pathology of a variety of diseases. The measurement of apoptosis will help us to evaluate the onset of disease and the effect of therapeutic interventions. In addition, the increased demand for understanding the early stages of apoptosis is pushing the envelope for solutions in early instance real-time monitoring of death kinetics. Here we present a novel electrochemiluminescent cytosensing strategy to quantitate apoptotic cell numbers, screen some anticancer drugs, and evaluate their effects on hepatocarcinoma cell line (HepG2) cells by utilizing the human antiphosphatidyl serine antibody (APSA) conjugated Ru­(bpy)<sub>3</sub><sup>2+</sup>-encapsulated silica nanoparticle (APSA-SiO<sub>2</sub>@Ru) as the detection probe. HepG2 cells were easily immobilized on the arginine-glycine-aspartic acid-serine (RGDS)-multiwalled carbon nanotubes (RGDS-MWCNTs) nanocomposite by the specific combination of RGD domains with integrin receptors on the cell surface. Then APSA-SiO<sub>2</sub>@Ru was introduced to the surface of apoptosis cells through the specific interaction between APSA and phosphatidylserine (PS) that distributed on the outer membrane of apoptotic cells. On the basis of the signal amplification of the APSA-SiO<sub>2</sub>@Ru nanoprobe, the cytosensor could respond as low as 800 cells mL<sup>–1</sup>, showing very high sensitivity. In addition, the dynamic alterations of surface PS expression on HepG2 cells in response to drugs and the cell heterogeneity were also demonstrated. The strategy presented a promising platform for highly sensitive cytosensing and convenient screening of some clinically available anticancer drugs

    Image_3_Antibacterial Activity and Mechanism of Action of Aspidinol Against Multi-Drug-Resistant Methicillin-Resistant Staphylococcus aureus.TIF

    No full text
    <p>This study aimed at investigating the antibacterial activity of aspidinol, an extract from Dryopteris fragrans (L.) Schott, against methicillin-resistant Staphylococcus aureus (MRSA). MRSA isolates were treated with aspidinol to determine the differential expression of genes and associated pathways following the drug treatment. Aspidinol displayed significant anti-MRSA activity, both in vivo (minimum inhibitory concentration = 2 μg/mL) and in vitro, and achieved an antibacterial effect comparable to that of vancomycin. In the lethal septicemic mouse study, a dose of 50 mg/kg of either aspidinol or vancomycin provided significant protection from mortality. In the non-lethal septicemic mouse study, aspidinol and vancomycin produced a significant reduction in mean bacterial load in murine organs, including the spleen, lung, and liver. After treatment with aspidinol, we found through RNA-seq and RT-PCR experiments that the inhibition of the formation of ribosomes was the primary S. aureus cell-killing mechanism, and the inhibition of amino acid synthesis and the reduction of virulence factors might play a secondary role.</p

    Surface morphology of CIP encapsulated PLGA magnetic particles by SEM.

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    <p>(A) CIP encapsulated in PLGA magnetic nanoparticles (B) CIP encapsulated in PLGA magnetic microparticles (C) CMX.</p

    Drug release from PLGA magnetic micro/nanoparticles.

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    <p>(A) Drug release in PBS buffer from PLGA magnetic micro/nanoparticles at 37°C and shaking at 100rpm. (B) Drug release from PLGA magnetic micro/nanoparticles under OMF and control drug release from PLGA magnetic micro/nanoparticles at 20°C without OMF. (C) Drug release from PLGA magnetic microparticles under OMF for initial 4hours then released in PBS buffer at 37°C and shaking at 100 rpm for another 15 days. (D) Drug release from PLGA magnetic nanoparticles under OMF for initial 4 hours then released in PBS buffer at 37°C and shaking at 100 rpm for another 15days.</p
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