Uptake of TiO₂ Nanoparticles into C. elegans Neurons Negatively Affects Axonal Growth and Worm Locomotion Behavior

We employ model organism Caenorhabditis elegans to effectively study the toxicology of anatase and rutile phase titanium dioxide (TiO₂) nanoparticles (NPs). The experimental results show that nematode C. elegans can take up fluorescein isothiocyanate-labeled TiO₂ NPs and that both anatase and rutile TiO₂ NPs can be detected in the cytoplasm of cultured primary neurons imaged by transmission electron microscopy. After TiO₂ NP exposure, these neurons also grow shorter axons, which may be related to the detected impeded worm locomotion behavior. Furthermore, anatase TiO₂ NPs did not affect the worm’s body length; however, we determined that a concentration of 500 μg/mL of anatase TiO₂ NPs reduced the worm population by 50% within 72 h. Notably, rutile TiO₂ NPs negatively affect both the body size and worm population. Worms unable to enter the L4 larval stage explain a severe reduction in the worm population at TiO₂ NPs LC₅₀/3d. To obtain a better understanding of the cellular mechanisms involved in TiO₂ NP intoxication, DNA microarray assays were employed to determine changes in gene expression in the presence or absence of TiO₂ NP exposure. Our data reveal that three genes (with significant changes in expression levels) were related to metal binding or metal detoxification (mtl-2, C45B2.2, and nhr-247), six genes were involved in fertility and reproduction (mtl-2, F26F2.3, ZK970.7, clec-70, K08C9.7, and C38C3.7), four genes were involved in worm growth and body morphogenesis (mtl-2, F26F2.3, C38C3.7, and nhr-247), and five genes were involved in neuronal function (C41G6.13, C45B2.2, srr-6, K08C9.7, and C38C3.7)

SPR setups and experimental procedures.

<p>(A) Schematic illustration of the SPR device: The He-Ne laser penetrated through a polarizer and a beam splitter, which split the beam 50/50. One was detected by a photodiode and the other one was coupled by a prism to generate Surface Plasmon Wave on the Au chip in which the angle shift was detected by a photodiode. (B) The OB-cadherin expressing cells flowing into the chamber were captured by the Au chip pre-coated with OB-cadherin antibodies, which changed the angle of the reflected laser beam. (C) A typical graphical data from SPR measurements.</p

Molecular biology detection of MSC-osteoblast differentiation.

<p>(A) Real-time PCR of OB-cadherin expression. (B) Western blot of OB-cadherin expression during osteogenic induction of MSCs. SaOS2 served as positive control. (C) The OB-cadherin expression level intensity analyzed by semi-quantitative method and was normalized to the intensity of SaOS2. (D) Alkaline phosphatase (AP) staining and von kossa (VK) staining.</p

HNO₃‑Assisted Polyol Synthesis of Ultralarge Single-Crystalline Ag Microplates and Their Far Propagation Length of Surface Plasmon Polariton

We developed a HNO₃-assisted polyol reduction method to synthesize ultralarge single-crystalline Ag microplates routinely. The edge length of the synthesized Ag microplates reaches 50 μm, and their top facets are (111). The mechanism for dramatically enlarging single-crystalline Ag structure stems from a series of competitive anisotropic growths, primarily governed by carefully tuning the adsorption of Ag⁰ by ethylene glycol and the desorption of Ag⁰ by a cyanide ion on Ag(100). Finally, we measured the propagation length of surface plasmon polaritons along the air/Ag interface under 534 nm laser excitation. Our single-crystalline Ag microplate exhibited a propagation length (11.22 μm) considerably greater than that of the conventional E-gun deposited Ag thin film (5.27 μm)

Surfactant-Directed Fabrication of Supercrystals from the Assembly of Polyhedral Au–Pd Core–Shell Nanocrystals and Their Electrical and Optical Properties

Au–Pd core–shell nanocrystals with cubic, truncated cubic, cuboctahedral, truncated octahedral, and octahedral structures have been employed to form micrometer-sized polyhedral supercrystals by both the droplet evaporation method and novel surfactant diffusion methods. Observation of cross-sectional samples indicates shape preservation of interior nanocrystals within a supercrystal. Low-angle X-ray diffraction techniques and electron microscopy have been used to confirm the presence of surfactant between contacting nanocrystals. By diluting the nanocrystal concentration or increasing the solution temperature, supercrystal size can be tuned gradually to well below 1 μm using the surfactant diffusion method. Rectangular supercrystal microbars were obtained by increasing the amounts of cubic nanocrystals and surfactant used. Au–Ag core–shell cubes and PbS cubes with sizes of 30–40 nm have also been fabricated into supercrystals, showing the generality of the surfactant diffusion approach to form supercrystals with diverse composition. Electrical conductivity measurements on single Au–Pd supercrystals reveal loss of metallic conductivity due to the presence of insulating surfactant. Cubic Au–Pd supercrystals show infrared absorption at 3.2 μm due to extensive plasmon coupling. Mie-type resonances centered at 9.8 μm for the Au–Pd supercrystals disappear once the Pd shells are converted into PdH after hydrogen absorption