Poly-γ-glutamate Binder To Enhance Electrode Performances of P2-Na_2/3Ni_1/3Mn_2/3O₂ for Na-Ion Batteries

P2-Na_2/3Ni_1/3Mn_2/3O₂ (P2-NiMn) is one of the promising positive electrode materials for high-energy Na-ion batteries because of large reversible capacity and high working voltage by charging up to 4.5 V versus Na⁺/Na. However, the capacity rapidly decays during charge/discharge cycles, which is caused by the large volume shrinkage of ca. 23% by sodium deintercalation and following electric isolation of P2-NiMn particles in the composite electrode. Serious electrolyte decomposition at the higher voltage region than 4.1 V also brings deterioration of the particle surface and capacity decay during cycles. To solve these drawbacks, we apply water-soluble sodium poly-γ-glutamate (PGluNa) as an efficient binder to P2-NiMn instead of conventional poly­(vinylidene difluoride) (PVdF) and examined the electrode performances of P2-NiMn composite electrode with PGluNa binder for the first time. The PGluNa electrode shows Coulombic efficiency of 95% at the first cycle and capacity retention of 89% after 50 cycles, whereas the PVdF electrode exhibits only 80 and 71%, respectively. The alternating current impedance measurements reveal that the PGluNa electrode shows a much lower resistance during the cycles compared with the PVdF one. From the surface analysis and peeling test of the electrodes, the PGluNa binder was found to cover the surface of the P2-NiMn particles and suppresses the electrolyte decomposition and surface degradation. The PGluNa binder further enhance the mechanical strength of the electrodes and suppresses the electrical isolation of the P2-NiMn particles during sodium extraction/insertion. The efficient binder with noticeable adhesion strength and surface coverage of active materials and carbon has paved a new way to enhance the electrochemical performances of high-voltage positive electrode materials for Na-ion batteries

Endoscopic findings in the esophagus on postirradiation day 1.

<p>In all dogs except one in the 25 J/cm² group, the mucosa at the site of irradiation (the area at 9 o’clock) showed reddish color changes on day 1 (A–C). Redness and ischemic color changes were observed at the site of irradiation in all dogs in the 50 J/cm² and 100 J/cm² groups (D–I).</p

Macroscopic findings in the esophagus.

<p>Mucosal redness and ulceration were observed in all dogs in the 25 J/cm² group (A–C). The areas of redness, erosion, and ulceration were more extensive in the 50 J/cm² and 100 J/cm² groups (D–I).</p

Laboratory data before and after irradiation.

<p>Compared with the baseline values, WBC count and CRP and LDH concentrations were increased with increasing radiation dose. WBC count and CRP and LDH concentrations returned to the baseline values on day 7 in the 25 J/cm² group but remained high, especially in the 100 J/cm² group.</p

Pathological findings in the injury areas.

<p>Notes) -: No abnormal changes, ±: Very slight, + : Slight, 2+: Moderate, 3+: Marked, NE: Not examined.</p><p>Cellular infiltration was observed in the mucosa, submucosa, muscle layer, and adventitia in the 25 J/cm² group. Cellular infiltration was observed within and outside of the adventitia in the 50 J/cm² and 100 J/cm² groups. Fibrosis and hemorrhage were observed in the submucosa, muscle layer, and adventitia in the 25 J/cm² group, and fibrosis and hemorrhage were observed within and outside of the adventitia in the 50 J/cm² and 100 J/cm² groups. Necrosis was observed in the submucosa and muscle layer in the 25 J/cm² group and within and outside of the adventitia in the 50 J/cm² and 100 J/cm² groups. These changes tended to become more severe as the irradiation dose increased.</p

Standard operation procedure for laser irradiation.

<p>The site of laser irradiation was fixed at 9 o’clock (A) in all animals because this direction was easiest for holding an endoscope stably and irradiating with a laser. Before laser irradiation, the site at 5 o’clock (B) was marked in advance with a clip. After completion of the laser irradiation (C), the site at 3 o’clock (D) was tattooed to identify the irradiation site for follow-up and autopsy.</p

Endoscopic findings in the esophagus on postirradiation day 7.

<p>Redness and slight bleeding were observed at the site of irradiation in all dogs on day 7. Ulceration was observed in the 25 J/cm² group (A–C) but was more extensive in both the 50 J/cm² and 100 J/cm² groups (D–I).</p

Controlled Growth and the Maintenance of Human Pluripotent Stem Cells by Cultivation with Defined Medium on Extracellular Matrix-Coated Micropatterned Dishes

<div><p>Here, we introduce a new serum-free defined medium (SPM) that supports the cultivation of human pluripotent stem cells (hPSCs) on recombinant human vitronectin-N (rhVNT-N)-coated dishes after seeding with either cell clumps or single cells. With this system, there was no need for an intervening sequential adaptation process after moving hPSCs from feeder layer-dependent conditions. We also introduce a micropatterned dish that was coated with extracellular matrix by photolithographic technology. This procedure allowed the cultivation of hPSCs on 199 individual rhVNT-N-coated small round spots (1 mm in diameter) on each 35-mm polystyrene dish (termed “patterned culture”), permitting the simultaneous formation of 199 uniform high-density small-sized colonies. This culture system supported controlled cell growth and maintenance of undifferentiated hPSCs better than dishes in which the entire surface was coated with rhVNT-N (termed “non-patterned cultures”). Non-patterned cultures produced variable, unrestricted cell proliferation with non-uniform cell growth and uneven densities in which we observed downregulated expression of some self-renewal-related markers. Comparative flow cytometric studies of the expression of pluripotency-related molecules SSEA-3 and TRA-1-60 in hPSCs from non-patterned cultures and patterned cultures supported this concept. Patterned cultures of hPSCs allowed sequential visual inspection of every hPSC colony, giving an address and number in patterned culture dishes. Several spots could be sampled for quality control tests of production batches, thereby permitting the monitoring of hPSCs in a single culture dish. Our new patterned culture system utilizing photolithography provides a robust, reproducible and controllable cell culture system and demonstrates technological advantages for the mass production of hPSCs with process quality control.</p></div

Culture of hPSCs with SPM on rhVNT-N coated dishes.

<p>(A) Phase contrast microscopic observation of iPSC cell line PFX#9 at passage 15. (B) Expression of SSEA-3 and TRA-1-60 by flow cytometric analysis of PFX#9 in indicated culture conditions at passage 15. (C) Time course of cell proliferation in patterned dish from days 1 to 4 (left to right). (D) Cell proliferation area that was occupied inrhVTN-N-coated spot area (spot Φ = 1 mm, 0.79 mm²/spot, X axis). Plot also shows the number of spots and their areas (out of 199 rhVNT-N-coated spots, Y axis) on days 1 to 4 (left to right). (E) Microscopic observations of clump cultures, single cell non-patterned or single cell patterned cultures with the higher magnified area in red rectangles at passage 20. A representative undifferentiated clump colony is shown in the upper left photo. Scale bars are appended. (F) Time course (0–100 h) of the area occupied by PFX#9 cells (in mm²) in 5 randomly selected spots (0.79 mm²/spot) measured by captured image analysis software (ImageJ 1.450, National Institutes of Health, Bethesda, MD, USA) every hour. Average of cell occupation area at every hour is plotted as a dot. The dot graph shows representative results from 3 independent trials. (G) Cell density (cells/mm²) of PFX#9 in single cell non-patterned or in single cell patterned culture was calculated by dividing harvested cell number by 962 mm² (35-mm non-patterned culture dish) or dividing harvested cell number by 156 mm² (total 199 spots of 1 mm diameter in 35-mm patterned culture dish). The results were obtained by scoring harvested cell numbers from 18 passages of indicated cultures and are shown as a bar (mean) with error bar (standard deviation). The significance of difference between 2 groups, p = 1.45 x 10⁻⁹. Representative results of 3 independent trials are shown. (H) Growth curve of PFX#9 in non-patterned culture, patterned culture or clump culture are shown in logarithmic graphs. PFX#9 cells in patterned culture or non-patterned culture were passaged every 4 days and in clump culture on feeder-free every 6 days and on feeder (SNL) every 5 days respectively.</p

Differentiation potential of hPSCs.

<p>(A) Gene expression profiles of PFX#9 cells in the indicated culture condition (clump culture, single cell non-patterned culture or single cell patterned culture) before (undifferentiated state) and after induction of differentiation via embryoid body (EB) formation. Average of gene expression values for self-renewal (undifferentiated state), ectoderm-, mesoderm- or endoderm-related genes is shown in comparison with reference standards of TaqMan hPSC Scorecard Panel (Life Technology). (B) EB formation at day 14 from PFX#9 cells (top left). EB attached to culture dish and continued to differentiate (top right). Cells were then stained with antibodies against β-tubulin (ectoderm), α-SMA (mesoderm), AFP (endoderm) and DAPI. (C) Tissue section of teratoma in NOG mouse generated by inoculating PFX#9 cells maintained in cell clumps is shown after staining with HE. Three germ layers of tissue consisting of neural rosette (ectoderm), muscle/cartilage (mesoderm) and gut-like epithelium (endoderm) are observed. Scores in Tables are visualized in bar graph below.</p