Showing papers by "David E. Cliffel published in 2011"
TL;DR: The results indicate that short-chain-length PEGs, regardless of termini, increase clearance rates compared to the previous long-chain PEG studies, while carboxylated termini increase red blood cell counts at high loadings, as well as the effects of a hydroxyl versus a carboxylic acid terminal functional group on the end of the PEG thiol on both clearance and immune response.
Abstract: Monolayer-protected gold nanoparticles have great potential as novel building blocks for the design of new drugs and therapeutics based on the easy ability to multifunctionalize them for biological targeting and drug activity. In order to create nanoparticles that are biocompatible in vivo, polyethylene glycol functional groups have been added to many previous multifunctionalized particles to eliminate nonspecific binding. Recently, monolayer-protected gold nanoparticles with mercaptoglycine functionalities were shown to elicit deleterious effects on the kidney in vivo that were eliminated by incorporating a long-chain, mercapto-undecyl-tetraethylene glycol at very high loadings into a mixed monolayer. These long-chain PEGs induced an immune response to the particle presumably generating an anti-PEG antibody as seen in other long-chain PEG-ylated nanoparticles in vivo. In the present work, we explore the in vivo effects of high and low percent ratios of a shorter chain, mercapto-tetraethylene glycol withi...
107 citations
TL;DR: Phase segregation and domain formation is observed within the protecting monolayer of gold nanoparticles using ion mobility-mass spectrometry, a two-dimensional gas-phase separation technique, providing evidence for nanophase separation resulting in anisotropic AuNPs.
Abstract: Phase segregation and domain formation is observed within the protecting monolayer of gold nanoparticles (AuNPs) using ion mobility-mass spectrometry, a two-dimensional gas-phase separation technique. Experimental data is compared to a theoretical model that represents a randomly distributed ligand mixture. Deviations from this model provide evidence for nanophase separation resulting in anisotropic AuNPs.
72 citations
TL;DR: A simulation for the photoelectrochemical behavior of an electrode modified with a monolayer of Photosystem I complexes during photochronoamperometric experiments in which the electrode is exposed to periods of darkness and irradiation is presented.
Abstract: Photosystem I (PSI), a photoactive protein complex that participates in the light reactions of natural photosynthesis, can exhibit photocatalytic capabilities when incorporated to electrochemical s...
32 citations
TL;DR: An analytic approach to the modeling of stop-flow amperometric measurements of cellular metabolism with thin glucose oxidase and lactate oxidase electrodes would provide a mechanistic understanding of the various factors that affect the measured signals.
Abstract: An analytic approach to the modeling of stop-flow amperometric measurements of cellular metabolism with thin glucose oxidase and lactate oxidase electrodes would provide a mechanistic understanding of the various factors that affect the measured signals. We divide the problem into two parts: (1) analytic formulas that provide the boundary conditions for the substrate and the hydrogen peroxide at the outer surface of the enzyme electrode layers and the electrode current expressed through these boundary conditions, and (2) a simple diffusion problem in the liquid compartment with the provided boundary conditions, which can be solved analytically or numerically, depending on the geometry of the compartment. The current in an amperometric stop-flow measurement of cellular glucose or lactate consumption/excretion is obtained analytically for two geometries, corresponding to devices developed at the Vanderbilt Institute for Integrative Biosystems Research and Education: a multianalyte nanophysiometer with effective one-dimensional diffusion and a multianalyte microphysiometer, for which plentiful data for metabolic changes in cells are available. The data are calibrated and fitted with the obtained time dependences to extract several cellular fluxes. We conclude that the analytical approach is applicable to a wide variety of measurement geometries and flow protocols.
18 citations
TL;DR: It is found that ionizing TNT lowers the reaction barrier for the initial step of this decomposition, and it is shown that a similar effect can occur if a positive moiety is bound to the TNT molecule.
Abstract: The unimolecular decomposition reaction of TNT can in principle be used to design ways to either detect or remove TNT from the environment. Here, we report the results of a density functional theory study of possible ways to lower the reaction barrier for this decomposition process by ionization, so that decomposition and/or detection can occur at room temperature. We find that ionizing TNT lowers the reaction barrier for the initial step of this decomposition. We further show that a similar effect can occur if a positive moiety is bound to the TNT molecule. The positive charge produces a pronounced electron redistribution and dipole formation in TNT with minimal charge transfer from TNT to the positive moiety.
14 citations
TL;DR: The detection of H5 HA protein demonstrates the logical extension of using these nanoparticle mimics as a safe positive control in the detection of influenza, making this a vital step in improving influenza detection methodology.
Abstract: Immunoassays are important tools for the rapid detection and identification of pathogens, both clinically and in the research laboratory. An immunoassay with the potential for the detection of influenza was developed and tested using hemagglutinin (HA), a commonly studied glycoprotein found on the surface of influenza virions. Gold nanoparticles were synthesized, which present multiple peptide epitopes, including the HA epitope, in order to increase the gravimetric response achieved with the use of a QCM immunosensor for influenza. Specifically, epitopes associated with HA and FLAG peptides were affixed to gold nanoparticles by a six-mer PEG spacer between the epitope and the terminal cysteine. The PEG spacer was shown to enhance the probability for interaction with antibodies by increasing the distance the epitope extends from the gold surface. These nanoparticles were characterized using thermogravimetric analysis, transmission electron microscopy, matrix-assisted laser desorption/ionization-time of flight, and 1H nuclear magnetic resonance analysis. Anti-FLAG and anti-HA antibodies were adhered to the surface of a QCM, and the response of each antibody upon exposure to HA, FLAG, and dual functionalized nanoparticles was compared with binding of Au–tiopronin nanoparticles and H5 HA proteins from influenza virus (H5N1). Results demonstrate that the immunoassay was capable of differentiating between nanoparticles presenting orthogonal epitopes in real-time with minimal nonspecific binding. The detection of H5 HA protein demonstrates the logical extension of using these nanoparticle mimics as a safe positive control in the detection of influenza, making this a vital step in improving influenza detection methodology.
14 citations
01 Aug 2011
1 citations
Patent•
05 Oct 2011TL;DR: In this paper, the optical limiting structure is configured to transition from a first optical state to a second optical state when the phase-change material is heated above a critical temperature, with transmittance of light at a predetermined wavelength through the optical limit structure being lower at the second optical states of the limiting structure in relation to the first optical states.
Abstract: A sensor device includes an optical limiting structure including a metal layer with at least one metal particle having a size no greater than about 1500 nm, and a phase-change material layer disposed adjacent at least a portion of the metal layer, the phase-change material layer including a phase-change material, and a dendritic-metal layer disposed over at least a portion of the phase-change material layer of the optical limiting structure, the dendritic-metal layer including an organic compound including branching chain amino acid groups attached to a metal structure. The optical limiting structure is configured to transition from a first optical state to a second optical state when the phase-change material is heated above a critical temperature, with transmittance of light at a predetermined wavelength through the optical limiting structure being lower at the second optical state of the optical limiting structure in relation to the first optical state of the optical limiting structure.