Cerium oxide nanoparticles protect against Aß-induced mitochondrial fragmentation and neuronal cell death.

Evidence indicates that nitrosative stress and mitochondrial dysfunction participate in the pathogenesis of Alzheimer's disease (AD). Amyloid beta (Aß) and peroxynitrite induce mitochondrial fragmentation and neuronal cell death by abnormal activation of dynamin-related protein 1 (DRP1), a large GTPase that regulates mitochondrial fission. The exact mechanisms of mitochondrial fragmentation and DRP1 overactivation in AD remain unknown; however, DRP1 serine 616 (S616) phosphorylation is likely involved. Although it is clear that nitrosative stress caused by peroxynitrite has a role in AD, effective antioxidant therapies are lacking. Cerium oxide nanoparticles, or nanoceria, switch between their Ce(3+) and Ce(4+) states and are able to scavenge superoxide anions, hydrogen peroxide and peroxynitrite. Therefore, nanoceria might protect against neurodegeneration. Here we report that nanoceria are internalized by neurons and accumulate at the mitochondrial outer membrane and plasma membrane. Furthermore, nanoceria reduce levels of reactive nitrogen species and protein tyrosine nitration in neurons exposed to peroxynitrite. Importantly, nanoceria reduce endogenous peroxynitrite and Aß-induced mitochondrial fragmentation, DRP1 S616 hyperphosphorylation and neuronal cell death.

Preparation and Characterization Challenges to Understanding Environmental and Biological Impacts of Nanoparticles.

Increasingly, it is recognized that understanding and predicting nanoparticle behavior is often limited by the degree to which the particles can be reliably produced and adequately characterized. Two examples that demonstrate how sample preparation methods and processing history may significantly impact particle behavior are: 1) an examination of cerium oxide (ceria) particles reported in the literature in relation to the biological responses observed and 2) observations related that influence synthesis and aging of ceria nanoparticles. Examining data from the literature for ceria nanoparticles suggests that thermal history is one factor that has a strong influence on biological impact. Thermal processing may alter many physicochemical properties of the particles, including density, crystal structure, and the presence of surface contamination. However, these properties may not be sufficiently recorded or reported to determine the ultimate source of an observed impact. A second example shows the types of difficulties that can be encountered in efforts to apply a well-studied synthesis route to producing well-defined particles for biological studies. These examples and others further highlight the importance of characterizing particles thoroughly and recording details of particle processing and history that too often are underreported.

Influence of Aging and Environment on Nanoparticle Chemistry - Implication to Confinement Effects in Nanoceria.

The oxidation state switching of cerium in cerium oxide nanoparticles is studied in detail. The influence of synthesis medium, aging time and local environment on the oxidation state switching, between +3 and + 4, is analyzed by tracking the absorption edge using UV-Visible spectroscopy. It is observed that by tuning the local environment, the chemistry of the nanoparticles could be altered. These time dependent, environmentally induced changes likely contribute to inconsistencies in the literature regarding quantum-confinement effects for ceria nanoparticles. The results in this article indicate that there is a need to carry out comprehensive analysis of nanoparticles while considering the influence of synthesis and processing conditions, aging time and local environment.

Thickness dependent self limiting 1-D tin oxide nanowire arrays by nanosecond pulsed laser irradiation.

Fast, sensitive and discriminating detection of hydrogen at room temperature is crucial for storage, transportation, and distribution of hydrogen as an energy source. One dimensional nanowires of SnO2 are potential candidates for improved H2 sensor performance. The single directional conducting continuous nanowires can decrease electrical noise, and their large active surface area could improve the response and recovery time of the sensor. In this work we discuss synthesis and characterization of nanowire arrays made using nanosecond ultraviolet wavelength (266 nm) laser interference processing of ultrathin SnO2 films on SiO2 substrates. The laser energy was chosen to be above the melting point of the films. The results show that the final nanowire formation is dominated by preferential evaporation as compared to thermocapillary flow. The nanowire height (and hence wire aspect ratio) increased with increasing initial film thickness h0 and with increasing laser energy density Eo. Furthermore, a self-limiting effect was observed where-in the wire formation ceased at a specific final remaining thickness of SnO2 that was almost independent of h0 for a given Eo. To understand these effects, finite element modeling of the nanoscale laser heating was performed. This showed that the temperature rise under laser heating was a strong non-monotonic function of film thickness. As a result, the preferential evaporation rate varies as wire formation occurs, eventually leading to a shut-off of evaporation at a characteristic thickness. This results in the stoppage of wire formation. This combination of nanosecond pulsed laser experiments and thermal modeling shows that several unique synthesis approaches can be utilized to control the nanowire characteristics.

Nanoceria as Antioxidant: Synthesis and Biomedical Applications.

The therapeutic application of nanomaterials has been a focus of numerous studies in the past decade. Due to its unique redox properties, cerium oxide (ceria) is finding widespread use in the treatment of medical disorders caused by the reactive oxygen intermediates (ROI). The radical-scavenging role of ceria nanoparticles (nanoceria) have been established, as well as the autocatalytic ability of nanoceria to regenerate under various environmental conditions. The synthesis of nanoceria in biocompatible media has also been reported along with cell viability in order to determine the potential use of nanoceria in biomedical applications.

Room temperature hydrogen detection using 1-D nanostructured tin oxide sensor.

Room temperature sensing of hydrogen using randomly oriented tin oxide nanowires has been demonstrated successfully. The role of surface functionalization of nanowires with platinum catalyst in rapid hydrogen detection is also studied. These nanowires were successfully incorporated into a micro-electro-mechanical (MEMS) device. The device can successfully detect hydrogen gas (as low as 500 ppm) with response time as low as 10 sec. Effect of aspect ratio of the nanowires on diffusion of hydrogen molecules in the tin oxide nanowires is elucidated in detail.

Spiral growth of one dimensional titania nanostructures using anodic oxidation.

One dimensional spiral titania nanostructures were obtained by anodization of pure titanium from fluoride containing solutions of phosphoric acid. The formation of nanotubes was found to be dependant on current density. Field Emission Scanning Electron Microscopy (FESEM) shows the diameter of tubes around 70-100 nm which is consistent with the High Resolution Transmission Electron Micrographs (HRTEM) and Atomic Force Microscopy (AFM) images. HRTEM showed the one dimensional growth as spiral in nature which was also supported by AFM images. This anisotropic growth is compared with the possible growth mechanisms.