A field effect gas sensor based on self-standing nanowire arrays

In this thesis we have introduced a novel gas sensor that works by fingerprinting the ionization breakdown characteristics of the unknown gases. This technique provides excellent selectivity; it is well established that at a constant temperature and pressure, every gas displays a unique breakdown electric field. In addition, because this technique does not involve adsorption or desorption of gases, the sensor exhibits a fast response and is not limited by considerations of reversibility and recovery. We employed vertically-aligned, self-standing arrays of gold nanowires (AuNWs) at one of the electrodes of a miniature parallel-plate ionization cell. The AuNW arrays were synthesized using a tailored version of the electrochemical template-assisted technique, resulting freestanding structures with controlled sparseness. Individual AuNWs, owing to their nanoscale tips, generate very high non-linear electric fields near their tips that provoke the breakdown process due to formation of a corona and allow self-sustaining discharges to be created at relatively low voltages. In an alternative approach, we exploited the tunneling field ionization characteristics of the gases to identify the unknown gas type and measure its concentration. The phenomenon of field ionization consists of electron tunneling from gas atoms (molecules) through a potential barrier into a vacant energy level of the conduction band of a metal. It has been widely used in field-ion microscopy and mass spectrometry. However, the electric fields required to field-ionize gaseous species are in the range of 2-5 V/Å, orders of magnitude higher than the breakdown fields. With the provision of low voltage operation, this method can be utilized in detection of gases at very low concentrations. In this research, we also fabricated sensors using AuNWs with particular tip geometry and composition capable of field-ionizing gas particles at sub-10V voltages. The devices were successfully characterized using several gas specie

Cells sorted off hiPSC-derived kidney organoids coupled with immortalized cells reliably model the proximal tubule

Abstract Of late, numerous microphysiological systems have been employed to model the renal proximal tubule. Yet there is lack of research on refining the functions of the proximal tubule epithelial layer—selective filtration and reabsorption. In this report, pseudo proximal tubule cells extracted from human-induced pluripotent stem cell-derived kidney organoids are combined and cultured with immortalized proximal tubule cells. It is shown that the cocultured tissue is an impervious epithelium that offers improved levels of certain transporters, extracellular matrix proteins collagen and laminin, and superior glucose transport and P-glycoprotein activity. mRNA expression levels higher than those obtained from each cell type were detected, suggesting an anomalous synergistic crosstalk between the two. Alongside, the improvements in morphological characteristics and performance of the immortalized proximal tubule tissue layer exposed, upon maturation, to human umbilical vein endothelial cells are thoroughly quantified and compared. Glucose and albumin reabsorption, as well as xenobiotic efflux rates through P-glycoprotein were all improved. The data presented abreast highlight the advantages of the cocultured epithelial layer and the non-iPSC-based bilayer. The in vitro models presented herein can be helpful in personalized nephrotoxicity studies

Stem Cell Differentiation Toward the Myogenic Lineage for Muscle Tissue Regeneration: A Focus on Muscular Dystrophy

Skeletal muscle tissue engineering is one of the important ways for regenerating functionally defective muscles. Among the myopathies, the Duchenne muscular dystrophy (DMD) is a progressive disease due to mutations of the dystrophin gene leading to progressive myofiber degeneration with severe symptoms. Although current therapies in muscular dystrophy are still very challenging, important progress has been made in materials science and in cellular technologies with the use of stem cells. It is therefore useful to review these advances and the results obtained in a clinical point of view. This article focuses on the differentiation of stem cells into myoblasts, and their application in muscular dystrophy. After an overview of the different stem cells that can be induced to differentiate into the myogenic lineage, we introduce scaffolding materials used for muscular tissue engineering. We then described some widely used methods to differentiate different types of stem cell into myoblasts. We highlight recent insights obtained in therapies for muscular dystrophy. Finally, we conclude with a discussion on stem cell technology. We discussed in parallel the benefits brought by the evolution of the materials and by the expansion of cell sources which can differentiate into myoblasts. We also discussed on future challenges for clinical applications and how to accelerate the translation from the research to the clinic in the frame of DMD.World Premier International Research Center Initiative (WPI

Online Monitoring of Superoxide Anions Released from Skeletal Muscle Cells Using an Electrochemical Biosensor Based on Thick-Film Nanoporous Gold

Online detection and accurate quantification of superoxide anions released from skeletal muscle tissue is important in both physiological and pathological contexts. Above certain physiologically redundant levels, superoxides may exert toxic effects. Here we present design, fabrication, and successful testing of a highly sensitive electrochemical superoxide biosensor based on nanoporous gold (NPG) immobilized with cytochrome-<i>c</i> (cyt-<i>c</i>). A significant 14-fold enhancement in the biosensor sensitivity was achieved using NPG instead of nonporous gold, enabling the device to quantify minuscule levels of superoxides. Such improvement was attributed to the very large surface-to-volume ratio of the NPG network. The average values of superoxide sensitivity and analytical limit of detection (LOD) were 1.90 ± 0.492 nA nM^–1 cm^–2 and 3.7 nM, respectively. The sensor was employed to measure the rates of superoxide release from C2C12 myoblasts and differentiated myotubes upon stimulation with an endogenous superoxide-producing drug. To account for the issue of sensor-to-sensor sensitivity variations, each sensor was individually calibrated prior to measurements of biologically released superoxides. For the drug concentrations studied, C2C12 superoxide generation rates varied from 0.03 to 0.2 pM min^–1 cell^–1, within the range of superoxide release rates from normally contracting to fatiguing skeletal muscle tissue. Electrochemically obtained results were validated using a fluorescent superoxide probe. Compared to other destructive methods, the NPG-based electrochemical biosensor provides unique advantages in tissue engineering because of its higher sensitivity and the ability to measure the levels of biologically released superoxides in real-time

Microphysiological systems in early stage drug development: Perspectives on current applications and future impact

Microphysiological systems (MPS) are making advances to provide more standardized and predictive physiologically relevant responses to test articles in living tissues and organ systems. The excitement surrounding the potential of MPS to better predict human responses to medicines and improving clinical translation is overshadowed by their relatively slow adoption by the pharmaceutical industry and regulators. Collaboration between multiorganizational consortia and regulators is necessary to build an understanding of the strengths and limitations of MPS models and closing the current gaps. Here, we review some of the advances in MPS research, focusing on liver, intestine, vascular system, kidney and lung and present examples highlighting the context of use for these systems. For MPS to gain a foothold in drug development, they must have added value over existing approaches. Ideally, the application of MPS will augment in vivo studies and reduce the use of animals via tiered screening with less reliance on exploratory toxicology studies to screen compounds. Because MPS support multiple cell types (e.g. primary or stem-cell derived cells) and organ systems, identifying when MPS are more appropriate than simple 2D in vitro models for understanding physiological responses to test articles is necessary. Once identified, MPS models require qualification for that specific context of use and must be reproducible to allow future validation. Ultimately, the challenges of balancing complexity with reproducibility will inform the promise of advancing the MPS field and are critical for realization of the goal to reduce, refine and replace (3Rs) the use of animals in nonclinical research

Development of Flexible Cell-Loaded Ultrathin Ribbons for Minimally Invasive Delivery of Skeletal Muscle Cells

Cell transplantation therapy provides a potential solution for treating skeletal muscle disorders, but cell survival after transplantation is poor. This limitation could be addressed by grafting donor cells onto biomaterials to protect them against harsh environments and processing, consequently improving cell viability in situ. Thus, we present here the fabrication of poly­(lactic-<i>co</i>-glycolic acid) (PLGA) ultrathin ribbons with “canal-like” structures using a microfabrication technique to generate ribbons of aligned murine skeletal myoblasts (C2C12). We found that the ribbons functionalized with a solution of 3,4-dihydroxy-l-phenylalanine (DOPA) and then coated with poly-l-lysine (PLL) and fibronectin (FN) improve cell attachment and support the growth of C2C12. The viability of cells on the ribbons is evaluated following the syringe-handling steps of injection with different needle sizes. C2C12 cells readily adhere to the ribbon surface, proliferate over time, align (over 74%), maintain high viability (over 80%), and differentiate to myotubes longer than 400 μm. DNA content quantification carried out before and after injection and myogenesis evaluation confirm that cell-loaded ribbons can safely retain cells with high functionality after injection and are suitable for minimally invasive cell transplantation

デバイス内で動き出す新しいイノチ

京都大学アカデミックデイ2019開催日時: 2019年9月15日（日）10:00-16:00会場: 京都大学吉田キャンパス 百周年時計台記念館主催: 学術研究支援室（URA室）, 研究推進部研究推進課, 国民との科学・技術対話ワーキンググループ京都大学の学術研究成果発信の一環として包括的に登