During growth of Geobacter species able to transfer electrons to electrodes, biofilms consisting of multiple cell layers accumulate on surfaces. These biofilms require pathways for efficient electron relay towards the electrode, and diffusion of protons and end products away from the electrode. We hypothesized that altering the geometry of current-collecting electrodes would improve diffusion of substrates into electricity-producing biofilms, and allow testing of hypotheses related to the limits of long-range electron transfer. Two designs exposing equal gold surface areas to cultures of Geobacter sulfurreducens were compared: one consisting of a rectangular gold electrode and the other an array of 10 mm wide lines separated by 100 mm of non-conductive material. In all experiments, the line array electrode stabilized at a current density 4-fold higher (per unit electrode surface area) after 140 h of growth (1600 mA cm À2 vs. 400 mA cm À2 ). Confocal imaging and cyclic voltammetry analysis demonstrated that because cells could grow at least 15 mm outward in a semicylinder from the gold lines, 4-fold more biomass could share each line electrode, compared to the rectangular geometry. The semicylinder-shaped biofilms did not fill in gaps between the electrodes after 300 h of growth, suggesting a limitation to the distance of useful between-cell electron transfer. The wider spacing of biofilms also improved the affinity of cells for acetate, especially under quiescent conditions.
Isolating and analyzing tumor-derived exosomes (TEX) can provide important information about the state of a tumor, facilitating early diagnosis and prognosis. Since current isolation methods are mostly laborious and expensive, we propose herein a fast and cost-effective method based on a magnetic nanoplatform to isolate TEX. In this work, we have tested our method using three magnetic nanostructures: (i) Ni magnetic nanowires (MNWs) (1500 × 40 nm), (ii) Fe3O4 nanorods (NRs) (41 × 7 nm), and (iii) Fe3O4 cube-octahedral magnetosomes (MGs) (45 nm) obtained from magnetotactic bacteria. The magnetic response of these nanostructures has been characterized, and we have followed their internalization inside canine osteosarcoma OSCA-8 cells. An overall depiction has been obtained using a combination of Fluorescence and Scanning Electron Microscopies. In addition, Transmission Electron Microscopy images have shown that the nanostructures, with different signs of degradation, ended up being incorporated in endosomal compartments inside the cells. Small intra-endosomal vesicles that could be precursors for TEX have also been identified. Finally, TEX have been isolated using our magnetic isolation method and analyzed with a Nanoparticle tracking analyzer (NanoSight). We observed that the amount and purity of TEX isolated magnetically with MNWs was higher than with NRs and MGs, and they were close to the results obtained using conventional non-magnetic isolation methods.
In this paper, we discuss the use of low frequency (up to 300 MHz) radio waves (RF) to detect and characterize electrical defects present in the dielectrics of emerging integrated circuit devices. As an illustration, the technique is used to monitor the impact of thermal cycling on the RF signal characteristics (S-parameters, such as S11 and S21) of electrically active defects in three dimensional (3D) interconnects. The observed changes in the electrical characteristics of the interconnects were traced to changes in the chemistry of the isolation dielectric used in the through silicon via (TSV) construction; specifically to the conversion of chemical intermediates such as non-bridging silanol (Si-OH) to bridging siloxane (Si-O-Si). We suggest that these “chemical defects” inherent in the ‘as-manufactured’ products may be responsible for some of the unexplained early reliability failures observed in TSV enabled 3D devices. This low frequency RF technique could be optimized to complement, and in some cases compete favorably with, other thin film metrology techniques, such as ellipsometry and Fourier transform infrared spectroscopy (FTIR), for mass production environments.
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