Elsevier BV Acta Medica Okayama 2214-1804 51 2026 Highly sensitive detection of cancer cells using a voltage-tuned terahertz chemical microscope 100972 EN Xue Ding Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Yuto Ohmi Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Jin Wang Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Hirofumi Inoue Department of Medical Support, Okayama University Hospital Toshihiko Kiwa Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Terahertz chemical microscopy (TCM) is a promising label-free technique for detecting biochemical interactions by monitoring changes in terahertz (THz) wave emission from semiconductor sensing plates. However, quantitative biological detection has been hindered by large plate-to-plate variations originating from uncontrolled depletion-layer electric fields formed during fabrication. These variations shift the response curve of THz amplitude and reduce reproducibility and sensitivity. Here, we introduce a voltage-tuned sensing plate that allows direct control of the depletion-layer electric field by applying a bias voltage to the Si layer of the sensing plate. This enables deliberate adjustment of surface potential and alignment of the THz response curve to the region of highest gain. Using lung adenocarcinoma cells (PC9) captured via AE1/AE3 antibodies targeting specific cell-surface antigens, we demonstrate that voltage tuning enhances detection sensitivity by up to 50-fold and restores linearity between THz amplitude and the logarithm of cell concentration, even in plates with negligible response at 0 V. These findings establish voltage control as a simple, universally applicable strategy to stabilize TCM performance, reduce fabrication-induced variability, and improve analytical sensitivity for biosensing and materials-analysis applications. No potential conflict of interest relevant to this article was reported.

MDPI AG Acta Medica Okayama 2079-6374 16 1 2026 Magnetic Detection of Cancer Cells Using Tumor-Homing Peptide-Modified Magnetic Nanoparticles 45 EN Shengli Zhou Department of Interdisciplinary Science and Engineering in Health Systems, Okayama University Yuji Furutani Department of Interdisciplinary Science and Engineering in Health Systems, Okayama University Kei Yamashita Department of Interdisciplinary Science and Engineering in Health Systems, Okayama University Sakuya Kako Department of Interdisciplinary Science and Engineering in Health Systems, Okayama University Kazunori Watanabe Department of Interdisciplinary Science and Engineering in Health Systems, Okayama University Toshihiko Kiwa Department of Interdisciplinary Science and Engineering in Health Systems, Okayama University Takashi Ohtsuki Department of Interdisciplinary Science and Engineering in Health Systems, Okayama University Magnetic nanoparticles (MNPs) provide a platform for target detection because of their magnetic responsiveness to alternating magnetic fields (AMFs). We developed a detection method using MNPs modified with tumor-homing peptides (THPs), PL1 and PL3, which selectively bind to protein components enriched in malignant tissues. THP-MNPs were synthesized using maleimide-PEG-NHS linkers and characterized using transmission electron microscopy. Human glioblastoma cancer U87MG and normal tissue-derived HEK293 cells were incubated with THP-MNPs, and the magnetic signals were measured using a high-temperature superconducting quantum interference device (SQUID) magnetometer under an AMF (1.06 kHz). Dark-field microscopy confirmed the preferential binding of THP-MNPs to U87MG cells. In the absence of cells, THP-MNPs exhibited AMF-dependent signal enhancement, which correlated with particle size reduction due to THP release. This increase was completely suppressed in the presence of U87MG cells, indicating a strong THP-mediated interaction. PL3-MNPs exhibited superior discrimination between malignant and non-malignant cells. These results demonstrate that SQUID-based magnetic measurements using THP-MNPs enable rapid and label-free cancer cell detection. No potential conflict of interest relevant to this article was reported.

MDPI Acta Medica Okayama 2079-6374 15 1 2025 Mapping Surface Potential in DNA Aptamer-Neurochemical and Membrane-Ion Interactions on the SOS Substrate Using Terahertz Microscopy 46 EN Kosei Morita Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Yuta Mitsuda Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Sota Yoshida Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Toshihiko Kiwa Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Jin Wang Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University In this study, we utilized a terahertz chemical microscope (TCM) to map surface potential changes induced by molecular interactions on silicon-on-sapphire (SOS) substrates. By functionalizing the SOS substrate with DNA aptamers and an ion-selective membrane, we successfully detected and visualized aptamer-neurochemical complexes through the terahertz amplitude. Additionally, comparative studies of DNA aptamers in PBS buffer and artificial cerebrospinal fluid (aCSF) were performed by computational structure modeling and terahertz measurements. Beyond neurochemicals, we also investigated calcium ions, measuring their concentrations in PDMS-fabricated micro-wells using minimal sample volumes. Our results highlight the capability of TCM as a powerful, label-free, and sensitive platform for the probing and mapping of surface potential arising from molecular interactions, with broad implications for biomedical diagnostics and research. No potential conflict of interest relevant to this article was reported.

Royal Society of Chemistry (RSC) Acta Medica Okayama 2635-0998 2 3 2023 All-in-one terahertz taste sensor: integrated electronic and bioelectronic tongues 620 626 EN Jin Wang Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Kenji Sakai Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Toshihiko Kiwa Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Taste sensors, also known as electronic tongues or bioelectronic tongues, are designed to evaluate food and beverages, as well as for medical diagnostics. These devices mimic the ability of the human tongue to detect and identify different tastes in liquid samples, such as sweet, sour, salty, bitter, and umami. In this study, a novel all-in-one terahertz taste sensor was proposed, which differs from traditional electrochemical approaches. This sensor utilizes terahertz technology for imaging and sensing chemical reactions on the terahertz semiconductor emitter surface. The surface can be functionalized with ion-sensitive membranes, proteins, DNA aptamers, and organic receptors, enabling the detection of various substances, such as solution pH, physiological ions, sugars, toxic chemicals, drugs, and explosives. Terahertz taste sensors offer several advantages, including being label-free, high sensitivity and selectivity, rapid response, minimal sample consumption, and the ability to detect non-charged chemical substances. By integrating multiple receptors or sensing materials on a single chip, the all-in-one terahertz taste sensor has significant potential for future taste substance detection, nutrition evaluation, metabolite and drug monitoring, and biomarker sensing. No potential conflict of interest relevant to this article was reported.

岡山大学大学院ヘルスシステム統合科学研究科 Acta Medica Okayama 2436-3227 4 2024 ヘルスシステム統合科学研究科国際シンポジウム報告 27 29 EN Toshihiko KIWA Faculty of Interdisciplinary Science and Engineering in Health Systems, Okayama University Naoki KANAYAMA Faculty of Interdisciplinary Science and Engineering in Health Systems, Okayama University Nahoko HARADA Faculty of Interdisciplinary Science and Engineering in Health Systems, Okayama University Rei HAKAMADA Faculty of Interdisciplinary Science and Engineering in Health Systems, Okayama University 10.18926/interdisciplinary/66895 No potential conflict of interest relevant to this article was reported.

MDPI Acta Medica Okayama 1424-8220 24 2 2024 Ultrathin Platinum Film Hydrogen Sensors with a Twin-T Type Notch Filter Circuit 548 EN Shoki Wakabayashi Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Yuki Oh Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Haruhito Nakayama Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Jin Wang Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Toshihiko Kiwa Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University In recent years, hydrogen energy has garnered attention as a potential solution for mitigating greenhouse gas emissions. However, concerns regarding the inherent risk of hydrogen gas leakage and potential explosions have necessitated the development of advanced sensors. Within our research group, we have innovated an ultrathin platinum (Pt) film hydrogen sensor that gauges resistance changes in Pt thin films when exposed to hydrogen gas. Notably, the sensitivity of each sensor is contingent upon the thickness of the Pt film. To address the challenge of detecting hydrogen using multiple sensors, we integrated the ultrathin Pt film as a resistance element within a twin-T type notch filter. This filter exhibits a distinctive reduction in output signals at a specific frequency. The frequency properties of the notch filter dynamically alter with changes in the resistance of the Pt film induced by hydrogen exposure. Consequently, the ultrathin Pt film hydrogen sensor monitors output signal variations around the notch frequency, responding to shifts in frequency properties. This innovative approach enables the electrical control of sensor sensitivity by adjusting the operating frequency in proximity to the notch frequency. Additionally, the simultaneous detection of hydrogen by multiple sensors was successfully achieved by interconnecting sensors with distinct notch frequencies in series. No potential conflict of interest relevant to this article was reported.

MDPI Acta Medica Okayama 1424-8220 23 1 2022 Thickness Measurement at High Lift-Off for Underwater Corroded Iron-Steel Structures Using a Magnetic Sensor Probe 380 EN Shoya Adachi Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Minoru Hayashi Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Taisei Kawakami Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Yuto Ando Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Jin Wang Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Kenji Sakai Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Toshihiko Kiwa Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Toshiyuki Ishikawa Department of Civil, Environmental and Applied System Engineering, Faculty of Environmental and Urban Engineering, Kansai University Keiji Tsukada Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Infrastructure facilities that were built approximately half a century ago have rapidly aged. Steel sheet piles, the inspection object in this study, are severely corroded, resulting in cave-in damages at wharfs. To solve such a problem, non-destructive inspection techniques are required. We previously demonstrated plate thickness measurement using extremely low-frequency eddy current testing. However, when the steel sheet piles are located in water, shellfish adhere to their surface, causing a lift-off of several tens of millimeters. Therefore, this large lift-off hinders the thickness measurement owing to fluctuations of magnetic signals. In this study, sensor probes with different coil diameters were prototyped and the optimum size for measuring steel sheet piles at high lift-off was investigated. Using the probes, the magnetic field was applied with a lift-off range from 0 to 80 mm, and the intensity and phase of the detected magnetic field were analyzed. Subsequently, by increasing the probe diameter, a good sensitivity was obtained for the thickness estimation with a lift-off of up to 60 mm. Moreover, these probes were used to measure the thickness of actual steel sheet piles, and measurements were successfully obtained at a high lift-off. No potential conflict of interest relevant to this article was reported.

MDPI Acta Medica Okayama 2072-666X 13 8 2022 Optimization of Microchannels and Application of Basic Activation Functions of Deep Neural Network for Accuracy Analysis of Microfluidic Parameter Data 1352 EN Feroz Ahmed Graduate School of Interdisciplinary Science and Engineering in Health Systems, Department of Medical Bioengineering, Okayama University Masashi Shimizu Graduate School of Interdisciplinary Science and Engineering in Health Systems, Department of Medical Bioengineering, Okayama University Jin Wang Graduate School of Interdisciplinary Science and Engineering in Health Systems, Department of Medical Bioengineering, Okayama University Kenji Sakai Graduate School of Interdisciplinary Science and Engineering in Health Systems, Department of Medical Bioengineering, Okayama University Toshihiko Kiwa Graduate School of Interdisciplinary Science and Engineering in Health Systems, Department of Medical Bioengineering, Okayama University The fabrication of microflow channels with high accuracy in terms of the optimization of the proposed designs, minimization of surface roughness, and flow control of microfluidic parameters is challenging when evaluating the performance of microfluidic systems. The use of conventional input devices, such as peristaltic pumps and digital pressure pumps, to evaluate the flow control of such parameters cannot confirm a wide range of data analysis with higher accuracy because of their operational drawbacks. In this study, we optimized the circular and rectangular-shaped microflow channels of a 100 mu m microfluidic chip using a three-dimensional simulation tool, and analyzed concentration profiles of different regions of the microflow channels. Then, we applied a deep learning (DL) algorithm for the dense layers of the rectified linear unit (ReLU), Leaky ReLU, and Swish activation functions to train and test 1600 experimental and interpolation of data samples which obtained from the microfluidic chip. Moreover, using the same DL algorithm, we configured three models for each of these three functions by changing the internal middle layers of these models. As a result, we obtained a total of 9 average accuracy values of ReLU, Leaky ReLU, and Swish functions for a defined threshold value of 6 x 10(-5) using the trial-and-error method. We applied single-to-five-fold cross-validation technique of deep neural network to avoid overfitting and reduce noises from data-set to evaluate better average accuracy of data of microfluidic parameters. No potential conflict of interest relevant to this article was reported.

MDPI Acta Medica Okayama 1420-3049 27 12 2022 Rational Design of Peptides Derived from Odorant-Binding Proteins for SARS-CoV-2-Related Volatile Organic Compounds Recognition 3917 EN Jin Wang Faculty of Interdisciplinary Science and Engineering in Health Systems, Okayama University Kenji Sakai Faculty of Interdisciplinary Science and Engineering in Health Systems, Okayama University Toshihiko Kiwa Faculty of Interdisciplinary Science and Engineering in Health Systems, Okayama University Peptides are promising molecular-binding elements and have attracted great interest in novel biosensor development. In this study, a series of peptides derived from odorant-binding proteins (OBPs) were rationally designed for recognition of SARS-CoV-2-related volatile organic compounds (VOCs). Ethanol, nonanal, benzaldehyde, acetic acid, and acetone were selected as representative VOCs in the exhaled breath during the COVID-19 infection. Computational docking and prediction tools were utilized for OBPs peptide characterization and analysis. Multiple parameters, including the docking model, binding affinity, sequence specification, and structural folding, were investigated. The results demonstrated a rational, rapid, and efficient approach for designing breath-borne VOC-recognition peptides, which could further improve the biosensor performance for pioneering COVID-19 screening and many other applications. No potential conflict of interest relevant to this article was reported.

AIP Publishing Acta Medica Okayama 2158-3226 12 3 2022 Magnetic thickness measurement for various iron steels using magnetic sensor and effect of electromagnetic characteristics 035109 EN Keiji Tsukada Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Minoru Hayashi Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Taisei Kawakami Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Shoya Adachi Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Kenji Sakai Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Toshihiko Kiwa Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Toshiyuki Ishikawa Faculty of Environmental and Urban Engineering Department of Civil, Environmental and Applied System Engineering, Kansai University Mohd Mawardi Saari Faculty of Electrical and Electronic Engineering, Universiti Malaysia Pahang Kengo Hori Nippon Steel Metal Products Co., Ltd. Kazumasa Hisazumi Nippon Steel Corp. Tomonori Tominaga Nippon Steel Corp. The diagnosis and prevention of the deterioration of iron-steel infrastructure has become an important social issue in recent years. The thickness measurement technique (extremely low-frequency eddy current testing (ELECT)) using a magnetic sensor for detecting steel corrosion at extreme frequency ranges has been previously reported. Using the calibration curves based on the correlation between the phase of the detected magnetic signal and the plate thickness, the plate thickness reduction caused by corrosion can be estimated from the detected phase signal. Iron-steel materials have large changes in electromagnetic characteristics; therefore, the reference calibration data for each type of iron-steel are required for plate thickness estimation. In this study, the effect of electromagnetic characteristics on the magnetic thickness measurement was investigated to improve the thickness estimation. Four types of iron-steel plates (SS400, SM400A, SM490A, and SMA400AW) with thicknesses ranging from 1 mm to 18 mm were measured by ELECT, and the phase change at multiple frequencies of each plate were analyzed. The shift in the phase and linearity regions of the calibration curves for each type of steel plate was observed. To analyze this shift phenomenon, the electromagnetic characteristics (permeability mu and conductivity sigma) of each type of steel were measured. Compared with the permeability mu and conductivity sigma of each steel plate in the applied magnetic field strength range, the product (sigma mu) for various steel plates decreased in the following order: SM400 > SS400 >SMA400AW > SM490A. The product of mu and sigma is related to the skin depth, indicating the electromagnetic wave attenuation and eddy current phase shift in the material. Therefore, each shift in the calibration curve of each type of iron steel is explained by the changes in the parameters sigma and mu. No potential conflict of interest relevant to this article was reported.

岡山大学全学教育・ 学生支援機構 Acta Medica Okayama 2432-9665 6 2021 Advances in Superconductivity as a road to meet Energy and Health SDGs: joint Japanese and European research teams may take the lead 148 165 EN Toshihiko Kiwa Okayama University Takayoshi Yokoya Okayama University Bernard Chenevier Okayama University Valeria Di Cosmo University of Turin Marco Truccato University of Turin William Sacks Sorbonne University, Faculty of Science and Engineering, Paris Wolfgang Sauerwein DGBNCT (Deutsche Gesellschaft für Bor-Neutroneneinfangtherapie e.V.) and University of Duisburg-Essen 10.18926/63338 Based on a statistical analysis of R&D activities in the field of superconductivity (SC) in a broad sense, the paper reports that Japan's leadership is strong over the past 20 years, in terms of researchers publications and patents. It also essentially shows that among the main world players, the Japanese normalized contribution is significantly dominating, although some trend towards a diminished leadership is observed in the data over the period 2005 -present time. Finally, the paper highlights that by taking advantage of their internationally recognized expertise in the field, joint Japanese and European research teams may advance superconductivity as a reliable road to meet Energy and Health SDGs (Sustainable Development Goals -UNESCO 2015). No potential conflict of interest relevant to this article was reported.

MDPI Acta Medica Okayama 2304-6732 9 1 2022 A Versatile Terahertz Chemical Microscope and Its Application for the Detection of Histamine 26 EN Jin Wang Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Kosuke Sato Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Yuichi Yoshida Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Kenji Sakai Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Toshihiko Kiwa Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Terahertz waves have gained increasingly more attention because of their unique characteristics and great potential in a variety of fields. In this study, we introduced the recent progress of our versatile terahertz chemical microscope (TCM) in the detection of small biomolecules, ions, cancer cells, and antibody-antigen immunoassaying. We highlight the advantages of our TCM for chemical sensing and biosensing, such as label-free, high-sensitivity, rapid response, non-pretreatment, and minute amount sample consumption, compared with conventional methods. Furthermore, we demonstrated its new application in detection of allergic-related histamine at low concentration in buffer solutions. No potential conflict of interest relevant to this article was reported.

MDPI Acta Medica Okayama 1424-8220 21 22 2021 Detection of Lung Cancer Cells in Solutions Using a Terahertz Chemical Microscope 7631 EN Yuichi Yoshida Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Xue Ding Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Kohei Iwatsuki Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Katsuya Taniizumi Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Hirofumi Inoue Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University Jin Wang Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Kenji Sakai Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Toshihiko Kiwa Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Cancer genome analysis has recently attracted attention for personalized cancer treatment. In this treatment, evaluation of the ratio of cancer cells in a specimen tissue is essential for the precise analysis of the genome. Conventionally, the evaluation takes at least two days and depends on the skill of the pathologist. In our group, a terahertz chemical microscope (TCM) was developed to easily and quickly measure the number of cancer cells in a solution. In this study, an antibody was immobilized on a sensing plate using an avidin-biotin reaction to immobilize it for high density and to improve antibody alignment. In addition, as the detected terahertz signals vary depending on the sensitivity of the sensing plate, the sensitivity was evaluated using pH measurement. The result of the cancer cell detection was corrected using the result of pH measurement. These results indicate that a TCM is expected to be an excellent candidate for liquid biopsies in cancer diagnosis. No potential conflict of interest relevant to this article was reported.

AIP Publishing Acta Medica Okayama 2158-3226 11 7 2021 Design and validation of microfluidic parameters of a microfluidic chip using fluid dynamics 75224 EN Feroz Ahmed Graduate School of Natural Science and Technology, Department of Medical Bioengineering, Okayama University Yuichi Yoshida Graduate School of Interdisciplinary Science and Engineering in Health Systems, Department of Medical Bioengineering, Okayama University Jin Wang Graduate School of Interdisciplinary Science and Engineering in Health Systems, Department of Medical Bioengineering, Okayama University Kenji Sakai Graduate School of Interdisciplinary Science and Engineering in Health Systems, Department of Medical Bioengineering, Okayama University Toshihiko Kiwa Graduate School of Interdisciplinary Science and Engineering in Health Systems, Department of Medical Bioengineering, Okayama University The internal fluidic parameters of microfluidic channels must be analyzed to solve fundamental microfluidic problems, including microscale transport problems involving thermal analysis, chemical reactivity, velocity, pressure drop, etc., for developing good-quality chemical and biological products. Therefore, the characterization and optimization of the interaction of chemical and biological solutions through microfluidic channels are vital for fluid flow design and engineering for quality assurance in microfluidic platforms. As the internal structures and kinetics of microfluidic channels are becoming increasingly complex, experiments involving optimal fluidic and transport designs are challenging to perform with high accuracy. However, highly integrated simulation tools can guide researchers without specialized computational fluid backgrounds to design numerical prototypes of highly integrated devices. In this study, a microfluidic chip with two inlet wells and one outlet well was fabricated from polydimethylsiloxane following which simulations were performed using an ANSYS Fluent tool influenced by computational fluid dynamics at a nearly identical scale. The pressure drop and velocity profiles of the interaction of two pH buffer solutions (pH 4 and 10) through the designed microfluidic chip were qualitatively estimated from experimental data analysis and validated with the simulation results obtained from the CFD-influenced ANSYS Fluent tool. No potential conflict of interest relevant to this article was reported.

AIP Publishing Acta Medica Okayama 2158-3226 10 1 2020 Laser monitoring of dynamic behavior of magnetic nanoparticles in magnetic field gradient EN Kenta Tsunashima Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Katsuya Jinno Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Bunta Hiramatsu Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Kayo Fujimoto Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Kenji Sakai Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Toshihiko Kiwa Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Mohd Mawardi Saari Faculty of Electrical & Electronic Engineering, Universiti Malaysia Pahang Keiji Tsukada Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Manipulation of magnetic nanoparticles (MNP) by an external magnetic field has been widely studied in the fields of biotechnology and medicine for collecting and/or reacting biomaterials in the solutions. Here, dynamic behaviors of MNP in solution under changing gradient magnetic field were investigated using our newly developed laser transmission system (LTS) with a variable magnetic field manipulator. The manipulator consists of a moving permanent magnet placed beside the optical cell filled with MNP solution. A laser beam was focused on the cell and the transmitted laser beam was detected by a silicon photodiode, so that the localized concentration of the MNP at the focused area could be evaluated by the intensity of transmitted laser beam. In this study, the LTS was applied to evaluate dynamic behaviors of MNP in serum solution. Dispersion and aggregation of MNP in the solution were evaluated. While time evolution of dispersion depends on the serum concentration, the behavior during aggregation by the magnetic field was independent of the serum concentration. A series of measurements for zeta-potentials, distributions of particle size, and magnetization distributions was carried out to understand this difference in the behavior. The results indicated that a Brownian motion was main force to distribute the MNP in the solution; on the other hand, the magnetic force to the MNP mainly affected the behavior during aggregation of the MNP in the solution. No potential conflict of interest relevant to this article was reported.

American Institute of Physics Acta Medica Okayama 2158-3226 9 12 2019 Magnetic characterization change by solvents of magnetic nanoparticles in liquid-phase magnetic immunoassay 125317 EN Katsuya Jinno Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Bunta Hiramatsu Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Kenta Tsunashima Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Kayo Fujimoto Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Kenji Sakai Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Toshihiko Kiwa Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Keiji Tsukada Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Liquid-phase magnetic immunoassay (MIA) using magnetic nano-particles (MNPs) has been studied as a more rapid method compared to optical methods for inspecting proteins and viruses. MIA can estimate the number of conjugated antibodies without being washed differently from conventional optical immunoassay. However, in the case of the liquid phase, it is considered that the magnetic properties of MNPs are affected by physical properties such as viscosity and impurity substances such as biological substances contained in the blood. In this study, the effect of sodium chloride (NaCl) in buffer and serum solution was evaluated to reveal the effect of serum because the sodium (Na+) and chloride (Cl-) ions in the serum dominate ion balance of blood. The measurement results of AC magnetic susceptibility and a dynamic light scattering (DLS) showed that the aggregation of MNPs was largely affected by the concentration of NaCl. This effect of the NaCl could be explained by shielding of the surface charge of MNPs by ions in the solution. Although the concentrations of NaCl in the buffer and serum solution were almost same, we found that MNPs were aggregated more in their size for those in the serum solution because of other impurities, such as proteins. These results suggest evaluation of effects of the contaminants in serum and optimization of polymer coatings of MNPs could be important factors to realize measurements of magnetic immunoassay with high accuracy. (C) 2019 Author(s). No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 133 2 2008 Analysis of response mechanism of a proton-pumping gate FET hydrogen gas sensor in air 538 542 EN Tomiharu Yamaguchi Masanori Takisawa Toshihiko Kiwa Hironobu Yamada Keiji Tsukada <p>Two different types of hydrogen response signals (DC and AC) of a proton-pumping gate FET with triple layer gate structure (Pd/proton conducting polymer/Pt) were obtained. The proton-pumping gate FET showed good selectivity against other gases (CH₄, C₂H₆, NH₃, and O₂). For practical use, the hydrogen response characteristics of the proton-pumping gate FET were investigated in air (a gaseous mixture of oxygen and nitrogen). The proton-pumping gate FET showed different hydrogen response characteristics in nitrogen as well as in air, despite the lack of oxygen interference independently. To clarify the response mechanism of the proton-pumping gate FET, a hydrogen response measurement was performed, using a gas flow system and electrochemical impedance spectroscopy. Consequently, the difference in response between nitrogen and air was found to be due to the hydrogen dissociation reaction and the interference with the proton transfer caused by the adsorbed oxygen on the upper Pd gate electrode</p> No potential conflict of interest relevant to this article was reported.