Design, synthesis and Chemical-physical characterization of photocatalytic inorganic nanocrystals for technological applications

This work was based on the synthesis and characterization of innovative crystals for biomedical and technological applications. Different types of syntheses were developed in order to obtain crystals with high photocatalytic properties. A hydrothermal synthesis was also processed to correlate the chemical-physical characteristics with synthesis parameters obtaining synthesis of nanoparticles of titanium dioxide with different morphology, size and crystalline phase depending on the variation of the synthesis parameters. Also a synthesis in water at 80 °C temperature and low pressure was developed from which anatase containing a small percentage of brookite nanoparticles were obtained, presenting a high photocatalytic activity. These particles have been used to obtain the microcrystals formed by an inorganic core of hydroxyapatite surface covered by TiO2 nanoparticles. Micrometer material with higher photocatalytic has been produced. The same nanoparticles have been functionalized with resorcinol oxidized in order to increase the photocatalytic efficiency. Photodegradation test results have confirmed this increase. Finally, synthetic nanoparticles with a waterless synthesis using formic acid and octanol, through esterification "in situ" were synthesized. Nanoparticles superficially covered by carboxylic residues able to bind a wide range of molecules to obtain further photocatalytic properties were obtained.

Application of a hybrid blocking layer in dye-sensitized solar cells

In dye-sensitized solar cells a blocking layer between the transparent electrode and the mesoporous titanium dioxide film is used to prevent short-circuits between the hole-conductor and the front electrode. The conventional approach is to use a compact layer of titanium dioxide prepared by spin coating or spray pyrolysis. The thickness of the blocking layer is critical. On one hand, the layer has to be thick enough to cover the rough substrate completely. On the other hand, the serial resistance increases with increasing film thickness, because the layer acts as an ohmic resistance itself. In this thesis an amphiphilic diblock copolymer is used as a functional template to produce an alternative, hybrid blocking layer. The hybrid blocking layer is thinner than the conventional, compact titanium dioxide film and thereby possesses a higher conductivity. Still, this type of blocking layer covers the rough electrode material completely and avoids current loss through charge recombination. The novel blocking layer is prepared using a tailored, amphiphilic block copolymer in combination with sol-gel chemistry. While the hydrophilic poly(ethylene oxide) part of the polymer coordinates a titanium dioxide precursor to form a percolating network of titania particles, the hydrophobic poly(dimethylsiloxane) part turns into an insulating ceramic layer. With this technique, crack-free films with a thickness down to 24 nm are obtained. The presence of a conductive titanium dioxide network for current flow, which is embedded in an insulating ceramic material, is validated by conductive scanning force microscopy. This is the first time that such a hybrid blocking layer is implemented in a solar cell. With this approach the efficiency could be increased up to 27 % compared to the conventional blocking layer. Thus, it is demonstrated that the hybrid blocking layer represents a competitive alternative to the classical approach.

Modifizierungen des Enzyms Silicatein alpha zur direkten Immobilisierung auf verschiedenen Oberflächen : neuartige Herstellung von Kompositmaterialien unter physiologischen Bedingungen

Das Silicatein α ist ein 24 kDa großes Enzym, welches im Schwamm Suberites domuncula für die Synthese von Biosilikat verantwortlich ist. Vorhergehende Studien haben gezeigt, dass Silicatein auch die Synthese anderer Metalloxide wie Titandioxid, Galliumoxid und Zirkoniumdioxid katalysieren kann. Diese Fähigkeiten machen das Silicatein α für biomedizinische und biotechnologische Anwendungen interessant, da die Synthese unter nahezu physiologischen Bedingungen ablaufen kann, was die Herstellung neuartiger Kompositmaterialien mit einzigartigen Eigenschaften erleichtern würde. Zur Immobilisierung des Silicatein α auf verschiedenen Oberflächen wurde bislang ein Nickel-NTA-Kopolymer eingesetzt. Diese Art der Immobilisierung bietet eine Reihe von Möglichkeiten in der Nanobiotechnologie, stößt aber in der Biomedizin an ihre Grenzen, da sich nicht alle Oberflächen für ein solches Coating eignen. Zudem können die zur Aktivierung des Polymers nötigen Lösungsmittel und die über die Zeit freigesetzten Monomere aus dem Polymergerüst toxische oder mutagene Wirkung auf das umliegende Gewebe haben. Deshalb wurde das Silicatein α in dieser Arbeit mit zwei Affinitäts-Tags so modifiziert, dass es an verschiedene Oberflächen immobilisiert werden kann und dabei seine Aktivität beibehält. Zuerst wurde das Silicatein mit einem Glu-tag am N-terminalen Ende modifiziert. Dadurch gelang die direkte Immobilisierung an Hydroxyapatit und die folgende, enzymkatalysierte Synthese von Biosilikat-Beschichtungen auf diesem Träger. Die Eigenschaften eines solchen HA-Kompositmaterials können zum Beispiel zu einem verbesserten, schnelleren und stabileren Einwachsen von Knochenimplantaten führen, da Biosilikat die Reifung und Differenzierung von Osteoblasten beschleunigt. rnMit dem an Hydroxyapatit-Plättchen immobilisierten Glu-tag-Silicatein wurde ein modifizierter Pull-down Assay etabliert, wodurch bekannte, aber auch bis dahin noch unbekannte Protein-Interaktionspartner identifiziert werden konnten. rnUm zu zeigen, dass der entwickelte Glu-tag an präformierte, calciumhaltige Oberflächen binden kann, wurden die Nadeln des Kalkschwammes Paraleucilla magna als Modellorganismus verwendet. Die Nadeln konnten durch das immobilisierte Silicatein mit einer Titandioxid-Schicht überzogen werden und unter Verwendung des Interaktionspartners Silintaphin-1 konnte diese Beschichtung noch verstärkt werden. Solche CaCO3-Kompositmaterialien könnten sowohl in der Biomedizin als auch in der Biotechnologie zum Einsatz kommen. Neben den erwähnten calciumhaltigen Materialien finden auch andere Stoffe wie TiO2-Nanodrähte Verwendung in der Forschung. In weiterführenden Experimenten konnte gezeigt werden, dass der entwickelte Glu-tag auch Affinität zu Titandioxid-Oberflächen vermittelt. Auch hier konnte durch das oberflächenimmobilisierte Enzym eine Biosilikatbeschichtung synthetisiert werden. rnMit der zweiten Modifikation - einem Cys-tag - konnte Silicatein direkt auf Goldoberflächen immobilisiert werden. Durch die Verwendung eines Polydimethylsiloxan (PDMS)-Stempels wurde das Cys-getaggte Silicatein in einem linienförmigen Muster auf das Gold übertragen und die Synthese von Titandioxid dort nachgewiesen.rnDie Experimente und Ergebnisse dieser Arbeit haben gezeigt, dass Silicatein α durch einfache Modifikationen an verschiedene Oberflächen immobilisiert werden kann und dabei immer noch seine Aktivität behält. rnHierdurch ergibt sich die Möglichkeit, unter Normalbedingungen verschiedenste Kompositmaterialien herzustellen.rn

Lichtsammler hinter Glas : Stabilisierung und Funktionalisierung des pflanzlichen Hauptlichtsammelkomplexes (LHCII) durch biomineralische Einbettung in Nanopartikel

Der Haupt-Lichtsammelkomplex des Fotosystems II (LHCII) setzt sich aus einem Proteinanteil und nicht-kovalent gebundenen Pigmenten – 8 Chlorophyll a, 6 Chlorophyll b und 4 Carotinoide - zusammen. Er assembliert in vivo zu einem Trimer, in dem die Monomereinheiten ebenfalls nicht-kovalent miteinander wechselwirken. Die ausgesprochen hohe Farbstoffdichte und die Tatsache, dass der Komplex rekombinant hergestellt werden kann, machen den LHCII zu einem interessanten Kandidaten für technische Anwendungen wie einer Farbstoffsolarzelle. Allerdings muss hierzu seine thermische Stabilität drastisch erhöht werden.rnDer Einschluss von Proteinen/Enzymen in Silikat erhöht deren Stabilität gegenüber Hitze signifikant. LHCII sollte als erster rekombinanter Membranproteinkomplex mittels kovalent verbundener, polykationischen Sequenzen in Silikat eingeschlossen werden. Hierzu wurde der Komplex auf zwei Weisen polykationisch modifiziert: Auf Genebene wurde die Sequenz des R5-Peptids in den N-terminalen Bereich des LHCP-Gens eingeführt und ein Protokoll zur Überexpression, Rekonstitution und Trimerisierung etabliert. Außerdem wurde eine kovalente Modifikation des trimeren LHCII mit dem Arginin-reichen Protamin über heterobifunktionelle Crosslinker entwickelt. Beide resultierenden LHCII-Derivate waren in der Lage, Silikat autogen zu fällen. Die Stabilisierung der so in Silikat präzipitierten Komplexe war jedoch deutlich geringer als bei nicht-modifizierten Komplexen, die durch eine Spermin-induzierte Copräzipitation eingeschlossenen wurden. Dabei zeigte sich, dass für den Anteil der eingebauten Komplexe und das Ausmaß an Stabilisierung die Größe und klare partikuläre Struktur des Silikats entscheidend ist. Kleine Partikel mit einem Durchmesser von etwa 20 nm führten zu einem Einbau von rund 75 % der Komplexe, und mehr als 80 % des Energietransfers innerhalb des Komplexes blieben erhalten, wenn für 24 Stunden bei 50°C inkubiert wurde. Nicht in Silikat eingeschlossene Komplexe verloren bei 50°C ihren Komplex-internen Energietransfer binnen weniger Minuten. Es war dabei unerheblich, ob die Partikelgröße durch die Wahl des Puffers und des entsprechenden pH-Wertes, oder aber durch Variation des Spermin-zu-Kieselsäure-Verhältnisses erreicht wurde. Wurden die polykationisch veränderten Komplexe in solchen Copräzipitationen verwendet, so erhöhte sich der Anteil an eingebauten Komplexen auf über 90 %, jedoch wurde nur bei der R5-modifizierten Variante vergleichbare Ausmaße an Stabilisierung erreicht. Ein noch höherer Anteil an Komplexen wurde in das Silikatpellet eingebaut, wenn LHCII kovalent mit Silanolgruppen modifiziert wurde (95 %); jedoch war das Ausmaß der Stabilisierung wiederum geringer als bei einer Copräzipitation. Die analysierten Fällungssysteme waren außerdem in der Lage, Titandioxid zu fällen, wobei der Komplex in dieses eingebaut wurde. Allerdings muss das Stabilisierungspotential hier noch untersucht werden. Innerhalb eines Silikatpräzipitats aggregierten die Komplexe nicht, zeigten aber einen inter-trimeren Energietransfer, der sehr wahrscheinlich auf einem Förster Resonanz Mechanismus basiert. rnDies und das hohe Maß an Stabilisierung eröffnen neue Möglichkeiten, rekombinanten LHCII in technischen Applikationen als Lichtsammelkomponente zu verwenden.rn

Oxidative stress and inflammation response after nanoparticle exposure: differences between human lung cell monocultures and an advanced three-dimensional model of the human epithelial airways

Combustion-derived and manufactured nanoparticles (NPs) are known to provoke oxidative stress and inflammatory responses in human lung cells; therefore, they play an important role during the development of adverse health effects. As the lungs are composed of more than 40 different cell types, it is of particular interest to perform toxicological studies with co-cultures systems, rather than with monocultures of only one cell type, to gain a better understanding of complex cellular reactions upon exposure to toxic substances. Monocultures of A549 human epithelial lung cells, human monocyte-derived macrophages and monocyte-derived dendritic cells (MDDCs) as well as triple cell co-cultures consisting of all three cell types were exposed to combustion-derived NPs (diesel exhaust particles) and to manufactured NPs (titanium dioxide and single-walled carbon nanotubes). The penetration of particles into cells was analysed by transmission electron microscopy. The amount of intracellular reactive oxygen species (ROS), the total antioxidant capacity (TAC) and the production of tumour necrosis factor (TNF)-alpha and interleukin (IL)-8 were quantified. The results of the monocultures were summed with an adjustment for the number of each single cell type in the triple cell co-culture. All three particle types were found in all cell and culture types. The production of ROS was induced by all particle types in all cell cultures except in monocultures of MDDCs. The TAC and the (pro-)inflammatory reactions were not statistically significantly increased by particle exposure in any of the cell cultures. Interestingly, in the triple cell co-cultures, the TAC and IL-8 concentrations were lower and the TNF-alpha concentrations were higher than the expected values calculated from the monocultures. The interplay of different lung cell types seems to substantially modulate the oxidative stress and the inflammatory responses after NP exposure.

Biomechanical effects of environmental and engineered particles on human airway smooth muscle cells

The past decade has seen significant increases in combustion-generated ambient particles, which contain a nanosized fraction (less than 100 nm), and even greater increases have occurred in engineered nanoparticles (NPs) propelled by the booming nanotechnology industry. Although inhalation of these particulates has become a public health concern, human health effects and mechanisms of action for NPs are not well understood. Focusing on the human airway smooth muscle cell, here we show that the cellular mechanical function is altered by particulate exposure in a manner that is dependent upon particle material, size and dose. We used Alamar Blue assay to measure cell viability and optical magnetic twisting cytometry to measure cell stiffness and agonist-induced contractility. The eight particle species fell into four categories, based on their respective effect on cell viability and on mechanical function. Cell viability was impaired and cell contractility was decreased by (i) zinc oxide (40-100 nm and less than 44 microm) and copper(II) oxide (less than 50 nm); cell contractility was decreased by (ii) fluorescent polystyrene spheres (40 nm), increased by (iii) welding fumes and unchanged by (iv) diesel exhaust particles, titanium dioxide (25 nm) and copper(II) oxide (less than 5 microm), although in none of these cases was cell viability impaired. Treatment with hydrogen peroxide up to 500 microM did not alter viability or cell mechanics, suggesting that the particle effects are unlikely to be mediated by particle-generated reactive oxygen species. Our results highlight the susceptibility of cellular mechanical function to particulate exposures and suggest that direct exposure of the airway smooth muscle cells to particulates may initiate or aggravate respiratory diseases.

Interaction of fine particles and nanoparticles with red blood cells visualized with advanced microscopic techniques

So far, little is known about the interaction of nanoparticles with lung cells, the entering of nanoparticles, and their transport through the blood stream to other organs. The entering and localization of different nanoparticles consisting of differing materials and of different charges were studied in human red blood cells. As these cells do not have any phagocytic receptors on their surface, and no actinmyosin system, we chose them as a model for nonphagocytic cells to study how nanoparticles penetrate cell membranes. We combined different microscopic techniques to visualize fine and nanoparticles in red blood cells: (I) fluorescent particles were analyzed by laser scanning microscopy combined with digital image restoration, (II) gold particles were analyzed by conventional transmission electron microscopy and energy filtering transmission electron microscopy, and (III) titanium dioxide particles were analyzed by energy filtering transmission electron microscopy. By using these differing microscopic techniques we were able to visualize and detect particles < or = 0.2 microm and nanoparticles in red blood cells. We found that the surface charge and the material of the particles did not influence their entering. These results suggest that particles may penetrate the red blood cell membrane by a still unknown mechanism different from phagocytosis and endocytosis.

Electron energy-loss spectroscopy as a tool for elemental analysis in biological speciments.

A transmission electron microscope (TEM) accessory, the energy filter, enables the establishment of a method for elemental microanalysis, the electron energy-loss spectroscopy (EELS). In conventional TEM, unscattered, elastic, and inelastic scattered electrons contribute to image information. Energy-filtering TEM (EFTEM) allows elemental analysis at the ultrastructural level by using selected inelastic scattered electrons. EELS is an excellent method for elemental microanalysis and nanoanalysis with good sensitivity and accuracy. However, it is a complex method whose potential is seldom completely exploited, especially for biological specimens. In addition to spectral analysis, parallel-EELS, we present two different imaging techniques in this chapter, namely electron spectroscopic imaging (ESI) and image-EELS. We aim to introduce these techniques in this chapter with the elemental microanalysis of titanium. Ultrafine, 22-nm titanium dioxide particles are used in an inhalation study in rats to investigate the distribution of nanoparticles in lung tissue.

Visualization and quantitative analysis of nanoparticles in the respiratory tract by transmission electron microscopy

ABSTRACT: Nanotechnology in its widest sense seeks to exploit the special biophysical and chemical properties of materials at the nanoscale. While the potential technological, diagnostic or therapeutic applications are promising there is a growing body of evidence that the special technological features of nanoparticulate material are associated with biological effects formerly not attributed to the same materials at a larger particle scale. Therefore, studies that address the potential hazards of nanoparticles on biological systems including human health are required. Due to its large surface area the lung is one of the major sites of interaction with inhaled nanoparticles. One of the great challenges of studying particle-lung interactions is the microscopic visualization of nanoparticles within tissues or single cells both in vivo and in vitro. Once a certain type of nanoparticle can be identified unambiguously using microscopic methods it is desirable to quantify the particle distribution within a cell, an organ or the whole organism. Transmission electron microscopy provides an ideal tool to perform qualitative and quantitative analyses of particle-related structural changes of the respiratory tract, to reveal the localization of nanoparticles within tissues and cells and to investigate the 3D nature of nanoparticle-lung interactions.This article provides information on the applicability, advantages and disadvantages of electron microscopic preparation techniques and several advanced transmission electron microscopic methods including conventional, immuno and energy-filtered electron microscopy as well as electron tomography for the visualization of both model nanoparticles (e.g. polystyrene) and technologically relevant nanoparticles (e.g. titanium dioxide). Furthermore, we highlight possibilities to combine light and electron microscopic techniques in a correlative approach. Finally, we demonstrate a formal quantitative, i.e. stereological approach to analyze the distributions of nanoparticles in tissues and cells.This comprehensive article aims to provide a basis for scientists in nanoparticle research to integrate electron microscopic analyses into their study design and to select the appropriate microscopic strategy.

Translocation of particles and inflammatory responses after exposure to fine particles and nanoparticles in an epithelial airway model

ABSTRACT: BACKGROUND: Experimental studies provide evidence that inhaled nanoparticles may translocate over the airspace epithelium and cause increased cellular inflammation. Little is known, however, about the dependence of particle size or material on translocation characteristics, inflammatory response and intracellular localization. RESULTS: Using a triple cell co-culture model of the human airway wall composed of epithelial cells, macrophages and dendritic cells we quantified the entering of fine (1 mum) and nano-sized (0.078 mum) polystyrene particles by laser scanning microscopy. The number distribution of particles within the cell types was significantly different between fine and nano-sized particles suggesting different translocation characteristics. Analysis of the intracellular localization of gold (0.025 mum) and titanium dioxide (0.02-0.03 mum) nanoparticles by energy filtering transmission electron microscopy showed differences in intracellular localization depending on particle composition. Titanium dioxide nanoparticles were detected as single particles without membranes as well as in membrane-bound agglomerations. Gold nanoparticles were found inside the cells as free particles only. The potential of the different particle types (different sizes and different materials) to induce a cellular response was determined by measurements of the tumour necrosis factor-alpha in the supernatants. We measured a 2-3 fold increase of tumour necrosis factor-alpha in the supernatants after applying 1 mum polystyrene particles, gold nanoparticles, but not with polystyrene and titanium dioxide nanoparticles. CONCLUSION: Quantitative laser scanning microscopy provided evidence that the translocation and entering characteristics of particles are size-dependent. Energy filtering transmission electron microscopy showed that the intracellular localization of nanoparticles depends on the particle material. Both particle size and material affect the cellular responses to particle exposure as measured by the generation of tumour necrosis factor-alpha.

A newly developed in vitro model of the human epithelial airway barrier to study the toxic potential of nanoparticles

The potential health effects of inhaled engineered nanoparticles are almost unknown. To avoid and replace toxicity studies with animals, a triple cell co-culture system composed of epithelial cells, macrophages and dendritic cells was established, which simulates the most important barrier functions of the epithelial airway. Using this model, the toxic potential of titanium dioxide was assessed by measuring the production of reactive oxygen species and the release of tumour necrosis factor alpha. The intracellular localisation of titanium dioxide nanoparticles was analyzed by energy filtering transmission electron microscopy. Titanium dioxide nanoparticles were detected as single particles without membranes and in membrane-bound agglomerates. Cells incubated with titanium dioxide particles showed an elevated production of reactive oxygen species but no increase of the release of tumour necrosis factor alpha. Our in vitro model of the epithelial airway barrier offers a valuable tool to study the interaction of particles with lung cells at a nanostructural level and to investigate the toxic potential of nanoparticles.

Effects of combustion-derived ultrafine particles and manufactured nanoparticles on heart cells in vitro

Evidence from epidemiological studies indicates that acute exposure to airborne pollutants is associated with an increased risk of morbidity and mortality attributed to cardiovascular diseases. The present study investigated the effects of combustion-derived ultrafine particles (diesel exhaust particles) as well as engineered nanoparticles (titanium dioxide and single-walled carbon nanotubes) on impulse conduction characteristics, myofibrillar structure and the formation of reactive oxygen species in patterned growth strands of neonatal rat ventricular cardiomyocytes in vitro. Diesel exhaust particles as well as titanium dioxide nanoparticles showed the most pronounced effects. We observed a dose-dependent change in heart cell function, an increase in reactive oxygen species and, for titanium dioxide, we also found a less organized myofibrillar structure. The mildest effects were observed for single-walled carbon nanotubes, for which no clear dose-dependent alterations of theta and dV/dt(max) could be determined. In addition, there was no increase in oxidative stress and no change in the myofibrillar structure. These results suggest that diesel exhaust as well as titanium dioxide particles and to a lesser extent also single-walled carbon nanotubes can directly induce cardiac cell damage and can affect the function of the cells.

Synthesis of PDMS-metal oxide hybrid nanocomposites using an in situ sol-gel route

Organic-inorganic hybrid nanocomposites are widely studied and applied in broad areas because of their ability to combine the flexibility, low density of the organic materials with the hardness, strength, thermal stability, good optical and electronic properties of the inorganic materials. Polydimethylsiloxane (PDMS) due to its excellent elasticity, transparency, and biocompatibility has been extensively employed as the organic host matrix for nanocomposites. For the inorganic component, titanium dioxide and barium titanate are broadly explored as they possess outstanding physical, optical and electronic properties. In our experiment, PDMS-TiO2 and PDMS-BaTiO3 hybrid nanocomposites were fabricated based on in-situ sol-gel technique. By changing the amount of metal precursors, transparent and homogeneous PDMS-TiO2 and PDMS-BaTiO3 hybrid films with various compositions were obtained. Two structural models of these two types of hybrids were stated and verified by the results of characterization. The structures of the hybrid films were examined by a conjunction of FTIR and FTRaman. The morphologies of the cross-sectional areas of the films were characterized by FESEM. An Ellipsometer and an automatic capacitance meter were utilized to evaluate the refractive index and dielectric constant of these composites respectively. A simultaneous DSC/TGA instrument was applied to measure the thermal properties. For PDMS-TiO2 hybrids, the higher the ratio of titanium precursor added, the higher the refractive index and the dielectric constant of the composites are. The highest values achieved of refractive index and dielectric constant were 1.74 and 15.5 respectively for sample PDMS-TiO2 (1-6). However, when the ratio of titanium precursor to PDMS was as high as 20 to 1, phase separation occurred as evidenced by SEM images, refractive index and dielectric constant decreased. For PDMS-BaTiO3 hybrids, with the increase of barium and titanium precursors in the system, the refractive index and dielectric constant of the composites increased. The highest value was attained in sample PDMS-BaTiO3 (1-6) with a refractive index of 1.6 and a dielectric constant of 12.2. However, phase separation appeared in SEM images for sample PDMS-BaTiO3 (1-8), the refractive index and dielectric constant reduced to lower values. Different compositions of PDMS-TiO2 and PDMS-BaTiO3 hybrid films were annealed at 60 °C and 100 °C, the influences on the refractive index, dielectric constant, and thermal properties were investigated.

NANOSCALE ELECTROCHEMISTRY BY IN-SITU TRANSMISSION ELECTRON MICROSCOPY

Nanoscale research in energy storage has recently focused on investigating the properties of nanostructures in order to increase energy density, power rate, and capacity. To better understand the intrinsic properties of nanomaterials, a new and advanced in situ system was designed that allows atomic scale observation of materials under external fields. A special holder equipped with a scanning tunneling microscopy (STM) probe inside a transmission electron microscopy (TEM) system was used to perform the in situ studies on mechanical, electrical, and electrochemical properties of nanomaterials. The nanostructures of titanium dioxide (TiO2) nanotubes are characterized by electron imaging, diffraction, and chemical analysis techniques inside TEM. TiO2 nanotube is one of the candidates as anode materials for lithium ion batteries. It is necessary to study their morphological, mechanical, electrical, and electrochemical properties at atomic level. The synthesis of TiO2 nanotubes showed that the aspect ratio of TiO2 could be controlled by processing parameters, such as anodization time and voltage. Ammonium hydroxide (NH4OH) treated TiO2 nanotubes showed unexpected instability. Observation revealed the nanotubes were disintegrated into nanoparticles and the tubular morphology was vanished after annealing. The nitrogen compounds incorporated in surface defects weaken the nanotube and result in the collapse of nanotube into nanoparticles during phase transformation. Next, the electrical and mechanical properties of TiO2 nanotubes were studied by in situ TEM system. Phase transformation of anatase TiO2 nanotubes into rutile nanoparticles was studied by in situ Joule heating. The results showed that single anatase TiO2 nanotubes broke into ultrafine small anatase nanoparticles. On further increasing the bias, the nanoclusters of anatase particles became prone to a solid state reaction and were grown into stable large rutile nanoparticles. The relationship between mechanical and electrical properties of TiO2 nanotubes was also investigated. Initially, both anatase and amorphous TiO2 nanotubes were characterized by using I-V test to demonstrate the semiconductor properties. The observation of mechanical bending on TiO2 nanotubes revealed that the conductivity would increase when bending deformation happened. The defects on the nanotubes created by deformation helped electron transportation to increase the conductivity. Lastly, the electrochemical properties of amorphous TiO2 nanotubes were characterized by in situ TEM system. The direct chemical and imaging evidence of lithium-induced atomic ordering in amorphous TiO2 nanotubes was studied. The results indicated that the lithiation started with the valance reduction of Ti4+ to Ti3+ leading to a LixTiO2 intercalation compound. The continued intercalation of Li ions in TiO2 nanotubes triggered an amorphous to crystalline phase transformation. The crystals were formed as nano islands and identified to be Li2Ti2O4 with cubic structure (a = 8.375 Å). This phase transformation is associated with local inhomogeneities in Li distribution. Based on these observations, a new reaction mechanism is proposed to explain the first cycle lithiation behavior in amorphous TiO2 nanotubes.

Biokinetics of nanoparticles and susceptibility to particulate exposure in a murine model of cystic fibrosis.

BACKGROUND Persons with cystic fibrosis (CF) are at-risk for health effects from ambient air pollution but little is known about the interaction of nanoparticles (NP) with CF lungs. Here we study the distribution of inhaled NP in a murine CF model and aim to reveal mechanisms contributing to adverse effects of inhaled particles in susceptible populations. METHODS Chloride channel defective CftrTgH (neoim) Hgu mice were used to analyze lung function, lung distribution and whole body biokinetics of inhaled NP, and inflammatory responses after intratracheal administration of NP. Distribution of 20-nm titanium dioxide NP in lungs was assessed on ultrathin sections immediately and 24 h after a one-hour NP inhalation. NP biokinetics was deduced from total and regional lung deposition and from whole body translocation of inhaled 30-nm iridium NP within 24 h after aerosol inhalation. Inflammatory responses were assessed within 7 days after carbon NP instillation. RESULTS Cftr mutant females had moderately reduced lung compliance and slightly increased airway resistance compared to wild type mice. We found no genotype dependent differences in total, regional and head deposition or in secondary-organ translocation of inhaled iridium NP. Titanium dioxide inhalation resulted in higher NP uptake by alveolar epithelial cells in Cftr mutants. Instillation of carbon NP induced a comparable acute and transient inflammatory response in both genotypes. The twofold increase of bronchoalveolar lavage (BAL) neutrophils in Cftr mutant compared to wild type mice at day 3 but not at days 1 and 7, indicated an impaired capacity in inflammation resolution in Cftr mutants. Concomitant to the delayed decline of neutrophils, BAL granulocyte-colony stimulating factor was augmented in Cftr mutant mice. Anti-inflammatory 15-hydroxyeicosatetraenoic acid was generally significantly lower in BAL of Cftr mutant than in wild type mice. CONCLUSIONS Despite lacking alterations in lung deposition and biokinetics of inhaled NP, and absence of significant differences in lung function, higher uptake of NP by alveolar epithelial cells and prolonged, acute inflammatory responses to NP exposure indicate a moderately increased susceptibility of lungs to adverse effects of inhaled NP in Cftr mutant mice and provides potential mechanisms for the increased susceptibility of CF patients to air pollution.