7 research outputs found

    Photoinitiated Nitric Oxide-Releasing Tertiary S -Nitrosothiol-Modified Xerogels

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    The synthesis of a tertiary thiol-bearing silane precursor (i.e., N-acetyl penicillamine propyltrimethoxysilane or NAPTMS) to enable enhanced NO storage stability at physiological temperature is described. The novel silane was co-condensed with alkoxy- and alkylalkoxysilanes under varied synthetic parameters (e.g., water to silane ratio, catalyst and solvent concentrations, and reaction time) to evaluate systematically the formation of stable xerogel films. The resulting xerogels were subsequently nitrosated to yield tertiary RSNO-modified coatings. Total NO storage ranged from 0.87–1.78 µmol cm−2 depending on the NAPTMS concentration and xerogel coating thickness. Steric hindrance near the nitroso functionality necessitated the use of photolysis to liberate NO. The average NO flux for irradiated xerogels in physiological buffer at 37 °C was ~23 pmol cm−2 s−1 (20% NAPTMS balance TEOS xerogel film cast using 30 µL). The biomedical utility of the photo-initiated NO-releasing films was illustrated by their ability to both reduce Pseudomonas aeruginosa adhesion by ~90% relative to control interfaces and eradicate the adhered bacteria

    Fluorinated benzalkylsilane molecular rectifiers

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    We report on the synthesis and electrical properties of nine new alkylated silane self-assembled monolayers (SAMs) – (EtO)3Si(CH2)nN = CHPhX where n = 3 or 11 and X = 4-CF[subscript 3], 3,5-CF[subscript 3], 3-F-4-CF[subscript 3], 4-F, or 2,3,4,5,6-F, and explore their rectification behavior in relation to their molecular structure. The electrical properties of the films were examined in a metal/insulator/metal configuration, with a highly-doped silicon bottom contact and a eutectic gallium-indium liquid metal (EGaIn) top contact. The junctions exhibit high yields (>90%), a remarkable resistance to bias stress, and current rectification ratios (R) between 20 and 200 depending on the structure, degree of order, and internal dipole of each molecule. We found that the rectification ratio correlates positively with the strength of the molecular dipole moment and it is reduced with increasing molecular length.National Science Foundation (U.S.) (Award ECCS 1254757)Wake Forest University (Pilot Research Grant

    Examination of bacterial resistance to exogenous nitric oxide

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    While much research has been directed to harnessing the antimicrobial properties of exogenous NO, the possibility of bacteria developing resistance to such therapy has not been thoroughly studied. Herein, we evaluate potential NO resistance using spontaneous and serial passage mutagenesis assays. Specifically, Staphylococcus aureus, Methicillin-resistant S. aureus (MRSA), Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa were systematically exposed to NO-releasing 75mol% MPTMS-TEOS nitrosothiol particles at or below minimum inhibitory concentration (MIC) levels. In the spontaneous mutagenesis assay, bacteria that survived exposure to lethal concentrations of NO showed no increase in MIC. Similarly, no increase in MIC was observed in the serial passage mutagenesis assay after exposure of these species to sub-inhibitory concentrations of NO through 20 d

    Photoinitiated Nitric Oxide-Releasing Tertiary <i>S</i>-Nitrosothiol-Modified Xerogels

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    The synthesis of a tertiary thiol-bearing silane precursor (i.e., <i>N</i>-acetyl penicillamine propyltrimethoxysilane or NAPTMS) to enable enhanced NO storage stability at physiological temperature is described. The novel silane was co-condensed with alkoxy- or alkylalkoxysilanes under varied synthetic parameters (e.g., water to silane ratio, catalyst and solvent concentrations, and reaction time) to evaluate systematically the formation of stable xerogel films. The resulting xerogels were subsequently nitrosated to yield tertiary RSNO-modified coatings. Total NO storage ranged from 0.87 to 1.78 μmol cm<sup>–2</sup> depending on the NAPTMS concentration and xerogel coating thickness. Steric hindrance near the nitroso functionality necessitated the use of photolysis to liberate NO. The average NO flux for irradiated xerogels (20% NAPTMS balance TEOS xerogel film cast using 30 μL) in physiological buffer at 37 °C was ∼23 pmol cm<sup>–2</sup> s<sup>–1</sup>. The biomedical utility of the photoinitiated NO-releasing films was illustrated by their ability to both reduce <i>Pseudomonas aeruginosa</i> adhesion by ∼90% relative to control interfaces and eradicate the adhered bacteria

    Role of Size and Shape on Biofilm Eradication for Nitric Oxide-Releasing Silica Nanoparticles

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    Nitric oxide (NO), a reactive free radical, has proven effective in eradicating bacterial biofilms with reduced risk of fostering antibacterial resistance. Herein, we evaluated the efficacy of NO-releasing silica nanoparticles against Gram-negative <i>Pseudomonas aeruginosa</i> and Gram-positive <i>Staphylococcus aureus</i> biofilms as a function of particle size and shape. Three sizes of NO-releasing silica nanoparticles (i.e., 14, 50, and 150 nm) with identical total NO release (∼0.3 μmol/mg) were utilized to study antibiofilm eradication as a function of size. To observe the role of particle shape on biofilm killing, we varied the aspect ratio of the NO-releasing silica particles from 1 to 8 while maintaining constant particle volume (∼0.02 μm<sup>3</sup>) and NO-release totals (∼0.7 μmol/mg). Nitric oxide-releasing particles with decreased size and increased aspect ratio were more effective against both <i>P. aeruginosa</i> and <i>S. aureus</i> biofilms, with the Gram-negative species exhibiting the greatest susceptibility to NO. To further understand the influence of these nanoparticle properties on NO-mediated antibacterial activity, we visualized intracellular NO concentrations and cell death with confocal microscopy. Smaller NO-releasing particles (14 nm) exhibited better NO delivery and enhanced bacteria killing compared to the larger (50 and 150 nm) particles. Likewise, the rod-like NO-releasing particles proved more effective than spherical particles in delivering NO and inducing greater antibacterial action throughout the biofilm

    Examination of bacterial resistance to exogenous nitric oxide

    No full text
    While much research has been directed to harnessing the antimicrobial properties of exogenous NO, the possibility of bacteria developing resistance to such therapy has not been thoroughly studied. Herein, we evaluate potential NO resistance using spontaneous and serial passage mutagenesis assays. Specifically, Staphylococcus aureus, Methicillin-resistant S. aureus (MRSA), Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa were systematically exposed to NO-releasing 75mol% MPTMS-TEOS nitrosothiol particles at or below minimum inhibitory concentration (MIC) levels. In the spontaneous mutagenesis assay, bacteria that survived exposure to lethal concentrations of NO showed no increase in MIC. Similarly, no increase in MIC was observed in the serial passage mutagenesis assay after exposure of these species to sub-inhibitory concentrations of NO through 20 d
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