The Crystalline Structure of Copper Phthalocyanine Films on ZnO(11̅00)

The structure of copper phthalocyanine (CuPc) thin films (5–100 nm) deposited on single-crystal ZnO(11̅00) substrates by organic molecular beam deposition was determined from grazing-incidence X-ray diffraction reciprocal space maps. The crystal structure was identified as the metastable polymorph α-CuPc, but the molecular stacking was found to vary depending on the film thickness: for thin films, a herringbone arrangement was observed, whereas for films thicker than 10 nm, coexistence of both the herringbone and brickstone arrangements was found. We propose a modified structure for the herringbone phase with a larger monoclinic β angle, which leads to intrastack Cu–Cu distances closer to those in the brickstone phase. This structural basis enables an understanding of the functional properties (e.g., light absorption and charge transport) of (opto)­electronic devices fabricated from CuPc/ZnO hybrid systems

Electrophoretic Deposition of Gentamicin-Loaded Bioactive Glass/Chitosan Composite Coatings for Orthopaedic Implants

Despite their widespread application, metallic orthopaedic prosthesis failure still occurs because of lack of adequate bone-bonding and the incidence of post-surgery infections. The goal of this research was to develop multifunctional composite chitosan/Bioglass coatings loaded with gentamicin antibiotic as a suitable strategy to improve the surface properties of metallic implants. Electrophoretic deposition (EPD) was applied as a single-step technology to simultaneously deposit the biopolymer, bioactive glass particles, and the antibiotic on stainless steel substrate. The microstructure and composition of the coatings were characterized using SEM/EDX, XRD, FTIR, and TGA/DSC, respectively. The in vitro bioactivity of the coatings was demonstrated by formation of hydroxyapatite after immersion in simulated body fluid (SBF) in a short period of 2 days. High-performance liquid chromatography (HPLC) measurements indicated the release of 40% of the loaded gentamicin in phosphate buffered saline (PBS) within the first 5 days. The developed composite coating supported attachment and proliferation of MG-63 cells up to 10 days. Moreover, disc diffusion test showed improved bactericidal effect of gentamicin-loaded composite coatings against <i>S. aureus</i> compared to control non-gentamicin-loaded coatings

Mechanisms of Polymer-Templated Nanoparticle Synthesis: Contrasting ZnS and Au

We combine solution small-angle X-ray scattering (SAXS) and high-resolution analytical transmission electron microscopy (ATEM) to gain a full mechanistic understanding of substructure formation in nanoparticles templated by block copolymer reverse micelles, specifically poly­(styrene)-<i>block</i>-poly­(2-vinylpyridine). We report a novel substructure for micelle-templated ZnS nanoparticles, in which small crystallites (∼4 nm) exist within a larger (∼20 nm) amorphous organic–inorganic hybrid matrix. The formation of this complex structure is explained via SAXS measurements that characterize <i>in situ</i> for the first time the intermediate state of the metal-loaded micelle core: Zn²⁺ ions are distributed throughout the micelle core, which solidifies as a unit on sulfidation. The nanoparticle size is thus determined by the radius of the metal-loaded core, rather than the quantity of available metal ions. This mechanism leads to particle size counterintuitively decreasing with increasing metal content, based on the modified interactions of the metal-complexed monomers in direct contrast to gold nanoparticles templated by the same polymer

Control of Photocurrent Generation in Polymer/ZnO Nanorod Solar Cells by Using a Solution-Processed TiO₂ Overlayer

We report herein the fabrication of hybrid conjugated polymer/ZnO photovoltaic devices using ZnO nanorod structures prepared by electrodeposition and study the effect of introducing a second metal oxide overlayer using a TiCl₄ post-treatment. We use transient absorption spectroscopy, scanning electron microscopy, and photovoltaic device measurements to study the microstructure and charge generation properties of the hybrid films and the performance of the resulting devices. We show how the ZnO nanostructure can be controlled via the nanorod growth conditions and demonstrate that photovoltaic device performance can be optimized by controlling the nanostructure in this way. Moreover, we show that a large increase in photocurrent generation can be achieved by coating the ZnO surface with a thin layer of titanium oxide by treating the ZnO nanostructure with a TiCl₄ solution

Surface Termination and CO₂ Adsorption onto Bismuth Pyrochlore Oxides

The catalytic activity and gas-sensing properties of a solid are dominated by the chemistry of the surface atomic layer. This study is concerned with the characterization of the outer atomic surfaces of a series of cubic ternary oxides containing Bi­(III): Bi₂M₂O₇ (M = Ti, Zr, Hf), using low-energy ion scattering spectroscopy. A preferential termination in Bi and O is observed in pyrochlore Bi₂Ti₂O₇ and related cubic compounds Bi₂Zr₂O₇ and Bi₂Hf₂O₇, whereas all three components of the ternary oxide are present on the surface of a Bi-free pyrochlore oxide, Y₂Ti₂O₇. This observation can be explained based on the revised lone-pair model for post-transition-metal oxides. We propose that the stereochemically active lone pair resulting from O 2p-assisted Bi 6s–6p hybridization is more energetically favored at the surface than within a distorted bulk site. This leads to reduction of the surface energy of the Bi₂M₂O₇ compounds and, therefore, offers a thermodynamic driving force for the preferential termination in BiO_<i>x</i>-like structures. CO₂ adsorption experiments <i>in situ</i> monitored by diffuse reflectance IR spectroscopy show a high CO₂ chemisorption capacity for this series of cubic bismuth ternary oxides, indicating a high surface basicity. This can be associated with O 2p–Bi 6s–6p hybridized electronic states, which are more able to donate electronic density to adsorbed species than surface lattice oxygen ions, normally considered as the basic sites in metal oxides. The enhanced CO₂ adsorption of these types of oxides is particularly relevant to the current growing interest in the development of technologies for CO₂ reduction

Effect of pulmonary surfactant on the dissolution, stability and uptake of zinc oxide nanowires by human respiratory epithelial cells

<p>Inhaled nanoparticles (NPs) have high-deposition rates in the alveolar region of the lung but the effects of pulmonary surfactant (PS) on nanoparticle bioreactivity are unclear. Here, the impact of PS on the stability and dissolution of ZnO nanowires (ZnONWs) was investigated, and linked with their bioreactivity <i>in vitro</i> with human alveolar epithelial type 1-like cells (TT1). Pre-incubation of ZnONWs with Curosurf® (a natural porcine PS) decreased their dissolution at acidic pH, through the formation of a phospholipid corona. Confocal live cell microscopy confirmed that Curosurf® lowered intracellular dissolution, thus delaying the onset of cell death compared to bare ZnONWs. Despite reducing dissolution, Curosurf® significantly increased the uptake of ZnONWs within TT1 cells, ultimately increasing their toxicity after 24 h. Although serum improved ZnONW dispersion in suspension similar to Curosurf®, it had no effect on ZnONW internalization and toxicity, indicating a unique role of PS in promoting particle uptake. In the absence of PS, ZnONW length had no effect on dissolution kinetics or degree of cellular toxicity, indicating a less important role of length in determining ZnONW bioreactivity. This work provides unique findings on the effects of PS on the stability and toxicity of ZnONWs, which could be important in the study of pulmonary toxicity and epithelial-endothelial translocation of nanoparticles in general.</p

Multimetallic Microparticles Increase the Potency of Rifampicin against Intracellular <i>Mycobacterium tuberculosis</i>

<i>Mycobacterium tuberculosis</i> (<i>M.tb</i>) has the extraordinary ability to adapt to the administration of antibiotics through the development of resistance mechanisms. By rapidly exporting drugs from within the cytosol, these pathogenic bacteria diminish antibiotic potency and drive the presentation of drug-tolerant tuberculosis (TB). The membrane integrity of <i>M.tb</i> is pivotal in retaining these drug-resistant traits. Silver (Ag) and zinc oxide (ZnO) nanoparticles (NPs) are established antimicrobial agents that effectively compromise membrane stability, giving rise to increased bacterial permeability to antibiotics. In this work, biodegradable multimetallic microparticles (MMPs), containing Ag NPs and ZnO NPs, were developed for use in pulmonary delivery of antituberculous drugs to the endosomal system of <i>M.tb</i>-infected macrophages. Efficient uptake of MMPs by <i>M.tb</i>-infected THP1 cells was demonstrated using an <i>in vitro</i> macrophage infection model, with direct interaction between MMPs and <i>M.tb</i> visualized with the use of electron FIB-SEM tomography. The release of Ag NPs and ZnO NPs within the macrophage endosomal system increased the potency of the model antibiotic rifampicin by as much as 76%, realized through an increase in membrane disorder of intracellular <i>M.tb.</i> MMPs were effective at independently driving membrane destruction of extracellular bacilli located at the exterior face of THP1 macrophages. This MMP system presents as an effective drug delivery vehicle that could be used for the transport of antituberculous drugs such as rifampicin to infected alveolar macrophages, while increasing drug potency. By increasing <i>M.tb</i> membrane permeability, such a system may prove effectual in improving treatment of drug-susceptible TB in addition to <i>M.tb</i> strains considered drug-resistant

Multimetallic Microparticles Increase the Potency of Rifampicin against Intracellular <i>Mycobacterium tuberculosis</i>

<i>Mycobacterium tuberculosis</i> (<i>M.tb</i>) has the extraordinary ability to adapt to the administration of antibiotics through the development of resistance mechanisms. By rapidly exporting drugs from within the cytosol, these pathogenic bacteria diminish antibiotic potency and drive the presentation of drug-tolerant tuberculosis (TB). The membrane integrity of <i>M.tb</i> is pivotal in retaining these drug-resistant traits. Silver (Ag) and zinc oxide (ZnO) nanoparticles (NPs) are established antimicrobial agents that effectively compromise membrane stability, giving rise to increased bacterial permeability to antibiotics. In this work, biodegradable multimetallic microparticles (MMPs), containing Ag NPs and ZnO NPs, were developed for use in pulmonary delivery of antituberculous drugs to the endosomal system of <i>M.tb</i>-infected macrophages. Efficient uptake of MMPs by <i>M.tb</i>-infected THP1 cells was demonstrated using an <i>in vitro</i> macrophage infection model, with direct interaction between MMPs and <i>M.tb</i> visualized with the use of electron FIB-SEM tomography. The release of Ag NPs and ZnO NPs within the macrophage endosomal system increased the potency of the model antibiotic rifampicin by as much as 76%, realized through an increase in membrane disorder of intracellular <i>M.tb.</i> MMPs were effective at independently driving membrane destruction of extracellular bacilli located at the exterior face of THP1 macrophages. This MMP system presents as an effective drug delivery vehicle that could be used for the transport of antituberculous drugs such as rifampicin to infected alveolar macrophages, while increasing drug potency. By increasing <i>M.tb</i> membrane permeability, such a system may prove effectual in improving treatment of drug-susceptible TB in addition to <i>M.tb</i> strains considered drug-resistant

High-Resolution Analytical Electron Microscopy Reveals Cell Culture Media-Induced Changes to the Chemistry of Silver Nanowires

There is a growing concern about the potential adverse effects on human health upon exposure to engineered silver nanomaterials (particles, wires, and plates). However, the majority of studies testing the toxicity of silver nanomaterials have examined nominally “as-synthesized” materials without considering the fate of the materials in biologically relevant fluids. Here, in-house silver nanowires (AgNWs) were prepared by a modified polyol process and were incubated in three cell culture media (DMEM, RPMI-1640, and DCCM-1) to examine the impact of AgNW-medium interactions on the physicochemical properties of the AgNWs. High-resolution analytical transmission electron microscopy revealed that Ag₂S crystals form on the surface of AgNWs within 1 h of incubation in DCCM-1. In contrast, the incubation of AgNWs in RPMI-1640 or DMEM did <i>not</i> lead to sulfidation. When the DCCM-1 cell culture medium was separated into its small molecule solutes and salts and protein components, the AgNWs were found to sulfidize in the fraction containing small molecule solutes and salts but not in the fraction containing the protein component of the media. Further investigation showed the AgNWs did not readily sulfidize in the presence of isolated sulfur containing amino acids or proteins, such as cysteine or bovine serum albumin (BSA). The results demonstrate that the AgNWs can be transformed by the media before and during the incubation with cells, and therefore, the effects of cell culture media must be considered in the analysis of toxicity assays. Appropriate media and material controls must be in place to allow accurate predictions about the toxicity and, ultimately, the health risk of this commercially relevant class of nanomaterial

Bronchoalveolar lavage cells from rats at 1, 7 and 21 days after intratracheal instillation of silver nanoparticles (0.1 mg/kg).

<p>The effects of 20nm and 110 nm silver nanospheres capped with citrate (20cit, 110cit) or polyvinlypyrrolidone (20pvp, 110pvp) in Brown Norway rats (Panels A, B, C, D & E) and of 20 nm silver nanoparticles capped with citrate or pvp in Sprague Dawley rats (Panels F, G, H, I & J) are shown. Data expressed as mean ± SD, n = 5–6 for each group. *P<0.05, **P<0.001, ***P<0.0001 versus the water control (C) within each time-point; +P<0.05.</p