Spatial Distribution Of Gold Nanoparticles Research Articles

Interaction between bilirubin oxidase and Au nanoparticles distributed over dimpled titanium foil towards oxygen reduction reaction

Spatial distribution of enzymes on electrodes is a key point to understand and optimize bioelectrocatalysis, although not largely investigated. In this work, Ti nanodimples serve as a platform for getting a controlled spatial distribution of gold nanoparticles (AuNPs). By varying the thickness of the initial gold layer, AuNPs with average sizes ranging from 13±6, 46±12 to 81±13 nm are obtained. AFM and TEM allow to localize the AuNPs in the dimples. It is in particular highlighted that the smallest NPs are present not only at the bottom but also on the edges of the Ti dimple, with TiO2 layer in their close surrounding. Enzymatic O2 reduction by immobilized Myrothecium verrucaria bilirubin oxidase (Mv BOD) is then investigated on the different materials. After having demonstrated the occurrence of the bioelectrocatalytic reaction on AuNPs excluding the Ti surface, the efficiency of the catalysis is discussed as a function of the AuNP size. The shape and fitting of the cyclic voltammetry curves obtained with the smallest AuNPs suggest a decrease in the electron transfer rate as a consequence of the colocalization of AuNPs and semiconducting TiO2. Interestingly, high stability of the enzymatic current is obtained with the highest AuNPs even in the presence of high concentration of salts.

Exploiting Nonlinear Photoacoustic Signal Generation in Gold Nanospheres for Selective Detection in Serial 3D PA Tomography

The photoacoustic (PA) signal amplitude measured in gold nanosphere suspensions has been shown to increase nonlinearly with the incident excitation fluence. In this work, this effect is exploited to recover the spatial distribution of gold nanoparticles in tomographic 3D photoacoustic (PA) images against the background contrast provided by absorbers that exhibit a linear relationship between the PA signal amplitude and the fluence. Serial tomographic PA images of a tissue phantom containing gold nanospheres and a tissue-mimicking absorber were acquired. By assessing the linearity of the PA intensity voxel by voxel, the spatial distribution of the gold nanosphere suspension was recovered. The method is shown to enable the robust detection of gold nanoparticles.

Strong Ligand–Block Copolymer Interactions for Incorporation of Relatively Large Nanoparticles in Ordered Composites

For well-ordered block copolymer (BCP) nanocomposites containing nanoparticles (NPs), the ratio of NP core diameter (dcore) and BCP domain width (L) has been generally limited with dcore/L < 0.3 when NP/BCP interactions are relatively neutral or weak. Here, we systematically investigate the spatial distribution of gold nanoparticles (NP) ranging in size up to 0.8 times that of the target domain width in symmetric polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) using a hydrogen-bonding-mediated (H-bonding) assembly. NPs with core diameters (dcore) 2, 5, 9, and 15 nm are coated with ligands bearing phenol groups as the hydrogen-donating sites for H-bonding including 2-(11-mercaptoundecyl)hydroquinone and thiol-terminated poly(4-hydroxystyrene). These hydroxylated NPs are selectively incorporated into the P2VP block (domain width L = 7–37 nm) over a wide range of volume fractions (ϕ = 3–26 vol %). Particle distributions are biased toward the center of in the P2VP domains when dcore/L is greater than 0.3 and ...

Physical Property Control on the Cellular Uptake Pathway and Spatial Distribution of Nanoparticles in Cells.

Nanoparticles have been developed in broad biomedical research in terms of effective cellular interactions to treat and visualize diseased cells. Considering the charge and polar functional groups of proteins that are embedded in cellular membranes, charged nanoparticles have been strategically developed to enhance electrostatic cellular interactions. In this study, we show that cellular uptake efficiency, pathway, and spatial distribution of gold nanoparticles in a cell are significantly modulated based on the surface condition of gold nanoparticles and human cancer cells that were tuned by controlling the pH of the medium and by introducing an electron beam. Cellular uptake efficiency is increased when electrostatic attraction is induced between the cells and the gold nanoparticles. Cell surface modification changes the cellular uptake pathways of the gold nanoparticles and concentrates the gold nanoparticles at the membrane region. Surface modification of the gold nanoparticles also contributes to deep penetration and homogeneous spatial distributions in a cell.

Holographic kinetics for mixed volume gratings in gold nanoparticles doped photopolymer

A holographic kinetic model is proposed to quantitatively represent the dynamics of mixed volume gratings in a bulk gold nanoparticles (NPs) doped photopolymer. Due to the polymerization-driven multicomponent diffusion, the volume refractive index grating is induced by the periodic spatial distribution of photoproduct while the absorption grating is formed by the periodic spatial distribution of gold NPs. By simulating this model with the characterization of time varying absorption modulation, it is capable to describe the behavior of gold NPs in both the polymerization and the multicomponent diffusion process. The temporal evolution of refractive index modulation and absorption modulation can be extracted, respectively, from a diffraction efficiency curve by fitting the model. The established model could be an effective method for understanding the photophysical and photochemical mechanism of holographic nanocomposite.

Investigation of gold nanoparticles uptake and their tissue level distribution in rice plants by laser ablation-inductively coupled-mass spectrometry

The tissue level uptake and spatial distribution of gold nanoparticles (AuNPs) in rice (Oryza sativa L.) roots and shoots under hydroponic conditions was investigated using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Rice plants were hydroponically exposed to positively, neutrally, and negatively charged AuNPs [AuNP1(+), AuNP2(0), AuNP3(−)] with a core diameter of 2 nm. Plants were exposed to AuNPs having 1.6 mg Au/L for 5 days or 0.14 mg Au/L for 3 months to elucidate how the surface charges of the nanoparticles affects their uptake into living plant tissues. The results demonstrate that terminal functional groups greatly affected the AuNP uptake into plant tissues. Au concentration determined by LA-ICP-MS in 5 day treated rice roots followed this order: AuNP1(+) > AuNP2(0) > AuNP3(−) but this order was reversed for rice shoots, indicating preferential translocation of AuNP3(−). Bioimages revealed distributions of mesophyll and vascular AuNP dependent on organ or AuNP concentration.

Tailoring the Refractive Indices of Thin Film Polymer Metallic Nanoparticle Nanocomposites

We demonstrate how to tailor the spatial distribution of gold nanoparticles (Au-NPs) of different sizes within polystyrene (PS) thin, supported, film hosts, thereby enabling the connection between the spatial distribution of Au-NPs within the polymer film and the optical properties to be determined. The real, n, and imaginary parts, k, of the complex refractive indices N = n(λ)+ik(λ) of the nanocomposite films were measured as a function of wavelength, λ, using multivariable angle spectroscopic ellipsometry. The surface plasmon response of films containing nearly homogeneous Au-NP distributions were well described by predictions based on classical Mie theory and the Drude model. The optical spectra of samples containing inhomogeneous nanoparticle distributions manifest features associated with differences in the size and interparticle spacings as well as the proximity and organization of nanoparticles at the substrate and free surface.

WE‐E‐204B‐03: Feasibility of Bench‐Top Polychromatic Cone‐Beam X‐Ray Fluorescence Computed Tomography (XFCT) for In‐Phantom Detection of Gold Nanoparticles

Purpose: To examine the feasibility of quantifying concentration and spatial distribution of gold nanoparticles (GNPs) present within a small animal‐sized object by applying an x‐ray fluorescence computed tomography (XFCT) technique with a bench‐top, polychromatic, cone‐beam x‐ray source. Method and Materials: The Monte Carlo code MCNP5 was used to simulate the acquisition of gold fluorescence photons under a polychromatic cone‐beam XFCT scenario. Three 1 cm‐diameter columns containing saline solution with GNPs (≤ 2% gold by weight) were inserted into a 5 cm‐diameter cylindrical PMMA phantom. The phantom was irradiated by a 110 kVp x‐ray source, and the resulting gold fluorescence and Compton‐scattered photons were collected by a series of 11 energy‐sensitive tallies. A maximized‐likelihood iterative reconstruction algorithm was implemented to reconstruct the image of GNP distribution. The effects of attenuation of both the primary beam through the phantom and the gold fluorescence photons en route to the detector were corrected during the image reconstruction. The attenuation map of the phantom was known a priori, although it could have been easily measured with a transmission scan. Results: An accurate image of the GNP‐containing phantom was successfully reconstructed, with both spatial distribution and relative concentration of GNPs well defined. The pixel intensity of regions containing GNPs was linearly proportional to gold concentration, which would allow XFCT technique to quantify the GNP concentration and spatial distribution of an unknown sample. Conclusion: This study shows the feasibility of performing XFCT imaging using a bench‐top, polychromatic, cone‐beam x‐ray source. The current approach would make XFCT imaging accessible to applications where a synchrotron‐based XFCT imaging may be inapplicable, such as in vivo measurements of GNP biodistribution.

Amine-Rich Polyelectrolyte Multilayer Nanoreactors for in Situ Gold Nanoparticle Synthesis

In situ synthesis of inorganic clusters in polyelectrolyte multilayers (PEMs) has typically relied on free carboxylic acid groups as the binding sites, limiting the scheme to the loading of cationic precursor reagents. The use of amine groups for similar purposes has not been demonstrated because of the challenge of incorporating free amine groups that are not paired with the oppositely charged groups residing on the polyanion of the PEM. In this paper, we use specific PEM assembly conditions to produce ultrathin conformal films of PAH/PAA (poly(allylamine hydrochloride)/poly(acrylic acid)) and PAH/PSS (poly(styrene sulfonate)) that upon suitable postassembly treatment undergo substantial molecular rearrangements that generate free amine groups in the films. These PEMs are capable of binding anionic precursors including complexes widely used for the synthesis of gold nanoparticles. On the basis of our understanding of the gold binding mechanisms, we demonstrate systematic control over the size and spatial distribution of gold nanoparticles in the films by changing the PEM assembly and postassembly treatment conditions.

Adsorption of gold nanoparticles obtained by vacuum deposition on an amorphous polymer surface

Spatial distribution of gold nanoparticles obtained by vacuum deposition on the surface of amorphous polymers was studied within the limits of the cluster lattice model.