This bioartificial renal tubule device functioned to reabsorb water, glucose and sodium for approximately 10 days. This is the first report of successful long-term evaluation of a bioartificial renal tubule device. This device, in combination with continuous haemofiltration, may provide treatment to prevent complications of dialysis and raise the quality of life in chronic renal failure patients.
In recent years, all-solid-state batteries (ASSBs) have been attracting attention as the next generation batteries for electric vehicles, energy storage systems, etc. Despite the growing interest, there are still many challenges faced in the commercial use of ASSBs. One of the biggest issues is the internal resistance, especially generated at the interface between solid electrolyte and electrode. The internal resistance at the interface limits the charge-discharge cycling performances. In order to solve this issue, it is necessary to examine the chemical and physical interactions at the interface. In this study, we have performed a detailed characterization of a LiPON/LiCoO2 interface using time-of-flight secondary ion mass spectrometry, x-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and low-energy inverse photoelectron spectroscopy to obtain information on chemical species, chemical compositions, chemical states, and energy band diagrams. These powerful techniques have revealed that an interlayer between LiPON and LiCoO2 was formed due to the temperature rise during the manufacturing process. The temperature rise caused a change of the LiPON network structure and stimulated Co reduction in the LiCoO2 layer near the interface. Energy band diagram analysis suggests that the electron diffusion from LiPON to LiCoO2 may have triggered the reduction of Co. We concluded that the chemical changes that occur at the interface caused an increase in interfacial impedance. Preventing the chemical reduction of Co would be a key to minimize the internal resistance. In this article, the detailed chemical interactions between the LiPON and LiCoO2 layers will be discussed.
We investigated a portable bioartificial renal tubule device (BRTD) consisting of renal tubule cells and hollow fibers, to improve the quality of life of patients. It is necessary for a BRTD system to be compact. A compact portable BRTB requires transfection of an appropriate water channel or electrical pump genes in tubular epithelial cells, which should be based on physiological similarities to human kidney function. LLC-PK(1) cells, into which rat kidney aquaporin 1 (AQP1) cDNA was stably transfected, were evaluated for water transport ability. The expression and localization of water AQP1 were examined by Western blotting, RT-PCR, and immunofluorescence. To measure transcellular water permeation, a simple method was applied, using phenol red as a cell-impermeant marker of concentration. In contrast to wild-type LLC-PK(1) cells, rat AQP1-transfected cells had high transcellular osmotic water permeability. The expression of rat AQP1 mRNA (ratio of AQP1 to beta-actin mRNA) and protein bands (a 28-kDa band and a broad, 35- to 45-kDa band) was confirmed to be stably maintained until a population doubling level of 24. In AQP1-transfected LLCPK(1) cells, the protein was localized mainly to the basolateral side, but also the apical side, of the plasma membrane. Wild-type LLC-PK(1) cells were not stained at the plasma membrane. It is possible that enough AQP1-transfected tubule epithelial cells were supplied for a bioartificial renal tubule device.
To develop a bioartificial renal tubule system using renal tubular cells and porous polymer membrane hollow fibers, long-term maintenance of a confluent monolayer and the functionally differentiated condition of cells is essential. We examined the proliferation and functional differentiation of LLC-PK1 (Lewis-lung cancer porcine kidney 1) cells on two types of membranes: polysulfone and cellulose acetate. Cell proliferation was significantly higher on the polysulfone membrane than on the cellulose acetate membrane, and was enhanced by coating the membranes with various extracellular matrices. Confluent monolayer formation of cells was observed on matrix-coated polysulfone membrane but not on matrix-coated cellulose acetate membrane within 1 week. Cell proliferation continued for 3 weeks after confluent monolayer formation. Messenger RNA (mRNA) expression of glucose transporters, indicators of the functional differentiation of the LLC-PK1 cells, was observed in the polysulfone and cellulose acetate membrane groups, but was not observed in the nonporous polystyrene plate group under subconfluent conditions. Expression of glucose transporters mRNA was maintained for 3 weeks after confluent monolayer formation. Polysulfone membrane is more suitable than cellulose acetate membrane for a bioartificial renal tubule system with regard to LLC-PK1 cell proliferation. Extracellular matrix coating of the membrane further improves cell proliferation.
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