[The role of abnormal mitochondrial fusion and fission in PBDE-47-induced change in mitochondrial mass in PC12 cells].

Objective: To investigate the effect of 2, 2', 4, 4'-tetrabromodiphenyl ether (PBDE-47) on the mitochondrial mass in rat adrenal pheochromocytoma (PC12) cells and the potential mechanisms. Methods: Highly differentiated PC12 cells were divided into control, 1, 10 or 20 µmol/L PBDE-47-treated groups and cultured for 24 h. Transmission electron microscopy was employed to observe the changes in mitochondrial morphology and quantity in PC12 cells. Flow cytometry was used to measure the fluorescence intensity of Nonyl Acridine Orange (NAO) , a fluorescent indicator of mitochondrial membrane cardiolipin, to reflect mitochondria mass. Western blotting was used to determine the expression levels of Mitofusion 1 (Mfn1) and Fission 1 (Fis1) proteins. To further explore the role of abnormal mitochondrial fusion and fission in PBDE-47-induced mitochondrial mass changes, PC12 cells were divided into control group, 5 µmol/L M1 treatment group, 20 µmol/L PBDE-47 treatment group and 5 µmol/L M1+20 µmol/L PBDE-47 combined treatment group and cultured for 24 h, then the fluorescence intensity of NAO and expression levels of Mfn1 and Fis1 proteins were detected. Results: The control group showed numerous mitochondria with normal morphology, while the number of mitochondria decreased after PBDE-47 treatment. Especially, the disappeared cristae, swelling and vacuoles of mitochondria and decreased fluorescence intensity of NAO (P<0.05) were observed in 10 and 20 µmol/L PBDE-47-treated groups. Meanwhile, the expression levels of Mfn1 and Fis1 proteins in the 10 and 20 µmol/L PBDE-47-treated groups were significantly decreased compared with control group (P<0.05) . However, 5 µmol/L M1 co-treatment with 20 µmol/L PBDE-47 significantly increased the levels of Mfn1 and Fis1 proteins and fluorescence intensity of NAO compared with the 20 µmol/L PBDE-47 group (P<0.05) . Conclusion: PBDE-47 can inhibit the mitochondrial fusion and fission process, thus leading to damage of mitochondria mass in PC12 cells.

Edge effect of strained bilayer nanofilms for tunable multistability and actuation.

We employed both theoretical and computational models supported by experiments to study the multistable behavior of an edge-effect driven Si/Cr micro-claw. Our study showed that individual micro-claws demonstrate either monostability or bistability as the magnitude of the edge effect is varied.

Mechanically tough, elastic and stable rope-like double nanohelices.

Double helix nanostructures have been the object of intense theoretical and experimental investigations in recent years due to their various types of available materials and unique morphology. Among these structures, rope-like double nanohelices of two strands in contact along a line can be obtained using any one-dimensional nanostructure. In this work, we establish a novel theory for quantitatively exploring the statics and dynamics of rope-like double nanohelices by employing the concept of the extensible Cosserat curve. The rope-like double nanohelices are tough, relatively elastic, and mechanically stable, which agrees well with the experiments. The characteristics of the interaction between the two strands, the tensile modulus and the torque are precisely described and explained across the entire stretching region. The proposed model offers in depth quantitative insight into the mechanics of double helix nanostructures, and supplies a reliable reference for further experimental research.

Inter-sheet-effect-inspired graphene sensors: design, fabrication and characterization.

With their sub-nanometer inter-sheet spacing, few-layer graphenes (FLGs) are alignment-free building blocks for nanosensors based on the inter-sheet effects. In this paper, we have tackled the challenges towards batch fabrication of inter-sheet graphene sensors through controlled layer engineering, edge tailoring and selective electrode fabrication on different atomic layers. An oxygen plasma etching (OPE) technique is developed to remove graphene layer by layer, enabling the batch fabrication of FLGs in a controllable fashion because of the faster speed and readiness of patterning of this process as compared to the conventional mechanical exfoliation. Vapor sensing experiments have shown that 'inter-sheet' sensors possess a higher sensitivity than conventional 'intra-sheet' ones. Vapor sensitivity is improved more than two times in normalized resistance changes by taking the 'inter-sheet' design upon exposure to 0.5% ethanol-nitrogen mixture and 500 Pa water vapor environments, respectively. These remarkable improvements can mainly be attributed to the inter-sheet effects such as electron tunneling, chemical doping, physical insertion and enhanced edge effects. Such effects may result from molecule adsorption/desorption, force/displacement, pressure, surface tension or thermal energy, and can potentially remarkably enrich the applicable transduction mechanisms.

Long-range linear elasticity and mechanical instability of self-scrolling binormal nanohelices under a uniaxial load.

Mechanical properties of self-scrolling binormal nanohelices with a rectangular cross-section are investigated under uniaxial tensile and compressive loads using nanorobotic manipulation and Cosserat curve theory. Stretching experiments demonstrate that small-pitch nanohelices have an exceptionally large linear elasticity region and excellent mechanical stability, which are attributed to their structural flexibility based on an analytical model. In comparison between helices with a circular, square and rectangular cross-section, modeling results indicate that, while the binormal helical structure is stretched with a large strain, the stress on the material remains low. This is of particular significance for such applications as elastic components in micro-/nanoelectromechanical systems (MEMS/NEMS). The mechanical instability of a self-scrolling nanohelix under compressive load is also investigated, and the low critical load for buckling suggests that the self-scrolling nanohelices are more suitable for extension springs in MEMS/NEMS.

Image-based 3D reconstruction using helical nanobelts for localized rotations.

A variety of different methods exist for gathering three-dimensional information for micro- and nanoscale objects. Tilting of samples in a scanning electron microscope provides a non-destructive way of generating these data. Traditionally, the reconstruction of this image data is performed by stereo photogrammetric methods that compare features from two or three frames. We propose the application of techniques from the structure-from-motion community as being efficient, high-precision alternatives to stereo methods, which allows for automated utilization of a large number of sampled images. We propose the use of nanobelts to generate localized rotational motions. Using this method alleviates the demand of high-precision actuators, allows 360 degrees rotations, and provides a useful tool for micro- and nanomanipulation.

Stability and analysis of configuration-tunable bi-directional MWNT bearings.

We report on the energetic and structural stability of configuration-tunable, bi-directional linear bearings based on cap-less, partial segments engineered within individual multi-walled carbon nanotubes (MWNTs). Using computational models, we show that an externally applied excitation force can be used to select an operating bearing configuration with a desired stiffness and operating frequency. Our models also demonstrate the possibility of simultaneous, independent operation of multiple bearings within a single NT segment, paving the way towards ultra-high device densities with molecular-scale footprints.

Batch fabrication of carbon nanotube bearings.

Relative displacements between the atomically smooth, nested shells in multiwalled carbon nanotubes (MWNTs) can be used as a robust nanoscale motion enabling mechanism. Here, we report on a novel method suited for structuring large arrays of MWNTs into such nanobearings in a parallel fashion. By creating MWNT nanostructures with nearly identical electrical circuit resistance and heat transport conditions, uniform Joule heating across the array is used to simultaneously engineer the shell geometry via electric breakdown. The biasing approach used optimizes process metrics such as yield and cycle-time. We also present the parallel and piecewise shell engineering at different segments of a single nanotube to construct multiple, but independent, high density bearings. We anticipate this method for constructing electromechanical building blocks to be a fundamental unit process for manufacturing future nanoelectromechanical systems (NEMS) with sophisticated architectures and to drive several nanoscale transduction applications such as GHz-oscillators, shuttles, memories, syringes and actuators.