Ryo Ishihara

Artificial chaperone polymer-enhanced hybridisation enabled the sensitive and specific detection of hsa-miR-500a-3p, a liquid biopsy biomarker, from a 1.0 µL sample within 15 minutes using a portable surface-functionalised power-free microchip.

Extracellular vesicles (EVs) have emerged as promising biomarkers for liquid biopsies because of their responsiveness to various physiological conditions. However, their dynamic physical properties pose significant analytical challenges, which necessitates the development of novel detection methods. In this study, a portable surface-functionalized power-free microchip (SF-PF microchip) was developed that enables the detection of EVs without external pumps. In particular, the SF-PF microchip specifically detected EVs derived from metastatic breast cancer cells with a limit of detection of 5.0 × 10¹⁰ particles/mL. Moreover, the SF-PF microchip required only 2.0 µL of sample volume and completed the detection within approximately 20 min, offering a rapid and convenient approach for EV analysis. Furthermore, the SF-PF microchip successfully detected EVs in serum samples, which highlights its potential for clinical application in liquid biopsies. Graphical abstract

セルフリー核酸（cfNA）と呼ばれるわれわれの体液中に存在するDNAやRNAが低侵襲診断を可能とするリキッドバイオプシーのバイオマーカーとして注目を集めている。本稿ではcfNAを概説した後に，cfNAが体液中で安定に存在するメカニズムを紹介し，cfNAを“色”を利用して検出た研究をいくつか紹介する。

Extracellular vesicles (EVs), which are small membrane vesicles secreted from cells into bodily fluids, are promising candidates as biomarkers for various diseases. We propose a simple, highly sensitive method for detecting EVs using a microchip. The limit of detection (LOD) for EVs was improved 29-fold by changing the microchannel structure of the microchip and by optimizing the EV detection protocols. The height of the microchannel was changed from 25 to 8 µm only at the detection region, and the time for EV capture was extended from 5 to 10 min. The LOD was 6.3 × 10¹⁰ particles/mL, which is lower than the concentration of EVs in the blood. The detection time was 19 min, and the volume of EV solution used was 2.0 µL. These results indicate that an efficient supply of EVs to the detection region is effective in improving the sensitivity of EV detection. The proposed EV detection method is expected to contribute to the establishment of EV-based cancer point-of-care testing.

Hydrogen gas is a promising, clean, and highly efficient energy source. However, to use combustible H₂ gas safety, high-performance and safe gas leakage sensors are required. In this study, transparent and flexible platinum-catalyst-loaded tungsten trioxide (Pt/WO₃) nanoparticle-dispersed membranes were prepared as H₂ gas leakage sensors. The nanoparticle-dispersed membrane with a Pt:W compositional ratio of 1:13 was transparent and exhibited a sufficient color change in response to H₂ gas. The membrane containing 0.75 wt.% of Pt/WO₃ nanoparticles exhibited high transparency over a wide wavelength range and the largest transmittance change in response to H₂ gas among the others. The heat treatment of the particles at 573 K provided sufficient crystallinity and an accessible area for a gasochromic reaction, resulting in a rapid and sensitive response to the presence of H₂ gas. The lower limit of detection of the optimized Pt/WO₃ nanoparticle-dispersed membrane by naked eye was 0.4%, which was one-tenth of the minimum explosive concentration. This novel membrane was transparent as well as flexible and exhibited a clear and rapid color response to H₂. Therefore, it is an ideal candidate sensor for the safe and easy detection of H₂ gas leakage.

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Radiation-induced graft polymerization provides industrially superior functionalization schemes by selection of existing polymer substrates and design of graft chains. In this review, by a pre-irradiation method of the radiation-induced graft polymerization and subsequent chemical modifications, charged polymer chains grafted onto various components and shapes of the polymer substrates are described. The charged graft chains immobilized onto a porous hollow-fiber membrane captured proteins in multilayers via multipoint binding. A membrane onto which positively charged graft chains are immobilized, i.e., an anion-exchange porous hollow-fiber membrane, was commercialized in 2011 for the removal of undesirable proteins in the purification of pharmaceuticals. On the other hand, a membrane onto which negatively charged graft chains are immobilized, i.e., a cation-exchange porous hollow-fiber membrane, exhibited a low permeation flux for pure water; however, the prepermeation of an aqueous solution of magnesium chloride through the membrane restored the permeation flux because of ionic crosslinking of graft chains with magnesium ions. The charged graft chains provide a precipitation field for inorganic compounds such as insoluble cobalt ferrocyanide. The graft chains entangle or penetrate a precipitate owing to electrostatic interactions with the surface charge on the precipitate. Braids and wound filters composed of insoluble-cobalt-ferrocyanide-impregnated fibers are used for the removal of radiocesium from contaminated water at Tokyo Electric Power Co. (TEPCO) Fukushima Daiichi Nuclear Power Plant.