Katsutoshi Ooe

Blood Plasma Separation Device using Capillary Phenomenon

A microdevice for blood plasma separation using capillary phenomenon has been proposed in this work. Blood plasma can be separated by microcapillary channels fabricated by silicon bulk- micromachining process. The 2 times 3 cm2 device with 1 mm-thick consists of a silicon separation chip and a glass cover. The separation was relatively fast (less than 2 minutes) after a blood-drop (20 mul) was drawn into the channels until the flow stopped. The device was designed for collecting 1 mul of plasma. Due to the advantages in a small sample volume, no power consumption, made the device possible for a blood diagnosis on a chip which promises the applications in point-of-care testing (POCT).

Immobilization of e-polylysine onto the probe surface for molecular adsorption type endotoxin detection system

Patients with renal failure become not able to expel the waste product, and they accumulate the toxic products for themselves. They therefore must use the hemodialysis to weed out the metabolic decomposition product. Hemodialysis for chronic renal failure is the most popular treatment method with artificial organs. However, hemodialysis patients must continue the treatment throughout their life, the results of long term extracorporeal dialysis, those patients develop the various complications and diseases, for example, dialysis amyloidosis etc. Dialysis amyloidosis is one of the refractory complications, and the prevention of this complication is important. Recently, endotoxin is thought to be the most likely cause of the complication. Endotoxin is one of the major cell wall components of gram-negative bacteria, and it forms the complex with proteins and lipopolysaccharide (LPS). It has various biological activities, e.g. attack of fever, when it gets mixed into human blood. In addition, it is known that large amount of endotoxin exists in living environment, and medicine is often contaminated with endotoxin. When contaminated dialyzing fluids are used to hemodialysis, above-mentioned dialysis amyloidosis is developed. Therefore, it is important that the detection and removal of endotoxin from dialyzing fluids. Until now, the measurement methods using Limulus Amebosyte Lysate (LAL) reagent were carried out as the tests for the presence of endotoxin. However, these methods include several different varieties of measurement techniques. The following are examples of them, gelatinization method, turbidimetric assay method, colorimetric assay method and fluoroscopic method. However, these techniques needed 30-60 minutes for the measurement. From these facts, they are not able to use as a real-time endotoxin detector. The detection of endotoxin has needed to carry out immediately, for that reason, a new real-time detection method is desired. We focused attention to adsorption reaction between &egr;-polylysine and endotoxin. &egr;-polylysine has the structure of straight chain molecule composed by 25-30 residues made by lysine, and it is used as an antimicrobial agent, moreover, cellulose beads with immobilized &egr;-polylysine is used as the barrier filter for endotoxin removal. Therefore, it is expected that the endotoxin be adsorbed to the immobilized &egr;-polylysine onto the probe. As the result of this reaction, the mass of the probe is increased, and endotoxin can be detected by using of Quartz Crystal Microbalance (QCM). In our previous research, we have already acquired the proteins immobilization technique onto Au and Si surface. In this report, the proposal of molecular adsorption type endotoxin detection system, and the immobilization of &egr;-polylysine onto the probe are described. We use X-ray Photoelectron Spectroscopy (XPS) to confirm the &egr;-polylysine immobilization, and the adsorptive activity of immobilized &egr;-polylysine is measured by XPS and AFM. The purpose of this study is to bring about the realization of Real-time endotoxin detection system.

Evaluation of the MOSFET-type enzyme biosensor

As the population ages, the management of the health is one of the important problems. Development of the harmless medical machine based on MEMS technologies for human body will be the mainly research projects in the future. Before now, we developed the glucose sensor for using at Health Monitoring System (HMS) as one of the medical device based on micromechatronics. HMS is the device that monitors human health conditions continuously. For example, the monitoring target of HMS is the blood. The whole blood contains the manifold health index markers, and it is very important to measure them in the health care. Glucose sensor specifically detects the glucose of the blood, and it monitors the glucose concentration as blood sugar level. This glucose sensor had separated Au electrode’ which immobilized GOx. By utilizing this style, it becomes possible that the sensor part is easily miniaturized. In our previous work, GOx was immobilized onto Au electrode by using of SAMs (Self-Assembled Monolayor) method, and the sensor using this working electrode detected the glucose concentration of glucose aqueous solution. Furthermore, the miniaturization of Au electrode was realized. In this report, glucose sensor which immobilized GOx using the cross-link method was produced, and the performance comparison with the sensor using SAMs method was carried out. And we carried out operation confirmation of produced glucose sensor using dilution human serum and whole blood. In addition, the cholesterol sensor which immobilized cholesterol oxidase (ChOx), which specifically detects the cholesterol on the blood, onto separated Au electrode by cross-link method was produced. The immobilization of the ChOx was evaluated from the spectra of XPS, and the performance as a sensor was evaluated.

Evaluation of the MOSFET type biosensor using glucose oxidase

A lot of researches and developments of medical device based on micromechatronics are performed. We develop the glucose sensor for using at HMS (Health Monitoring System) as one of the devices of those. In the development of a glucose sensor, it is necessary that the efficient hybridization between enzyme (glucose oxidase : GOD) as receptor and semiconductor as transducer. We devised the biosensor which used GOD immobilized gold plate as a gate electrode of the MOSFET. By utilizing this type, it becomes possible that the sensor part is easily miniaturized. When the glucose was detected using this sensor, there was a signal with concentration dependence. Therefore, it was confirmed that the prototype glucose sensor operated as a biosensor. From the above results, MOSFET type biosensor with gate electrode which immobilized GOD produced in this paper seems to be enough available as a glucose sensor. For miniaturization of the system, we examined the relationship between size of the working electrode and detection sensitivity. Consideration of the electrode area was not needed to detect the signal sensitively from the glucose sensor. And when we changed glass reference electrode to Au electrode, the enough sensitivity was obtained, too.

Vibration-type particle separation device with piezoceramic vibrator

During hemanalysis, it is necessary to separate blood cells from whole blood. Many blood separation methods, for example, centrifugation and filtering, are in practical use. However, the use of these methods involves problems from the perspectives of processing speed and processing volume. We develop new types of blood separation devices that use piezo-ceramic vibrators. The first device uses a capillary. One end of the capillary is fixed to the device frame, and the other is fixed to a piezo-ceramic vibrator. The vibrator transmits bending waves to the capillary. This device can process only a small amount of solution; therefore, it is not suitable for hemanalysis. In order to solve this problem, we developed a second device; this device has a pair of thin glass plates with a small gap as a substitute for the capillary used in the first device. These devices are based on the fact that particles heavier than water move toward transverse velocity antinodes while those lighter than water move toward velocity nodes. In this report, we demonstrate the highspeed separation of silica microbeads and 50-vol% glycerol water by using these devices. The first device can separate the abovementioned solution within 3 min while the second can separate it within 1 min. Both devices are driven by a rectangular wave of 15 to 20 Vpp. Furthermore, it has been confirmed that red blood cells are separated from diluted whole blood using the first device within approximately 1 min. These devices have transparency, so they can compose as the analysis system with the chemical analyzer easily.

Examination of bacterial toxin measurement using Quartz crystal microbalance method

When renal failure patients undergo the hemodialysis, the endtoxin (ET) that is the bacterial toxin that causes the symptom such as generation of heat is measured as one of the pollution markers. Presently, because the high performance filtration equipment develops, the amount of ET in dyalysate water and solution was achieved under the ET standard value set by Japanese Society for Dialysis Therapy etc. However, the ET measurement is obligated to the moon a couple of degrees at the dialysis center etc. the measurement is needed for 30 minutes or more since it use batch method and rely on the chemical reaction. In this study, we paid attention to the polyamino acid named epsiv-polylisine (epsiv-PL) that can select and adsorb ET and the mass measurement using quartz crystal microbalance method (QCM). We aim to the development of the real-time ET measuring system using these. If it is achieved, the amount of ET can be monitored while blood is dialyzed. Moreover, it seems that treatment that discontinues dialyzing can be taken when it exceeds the reference value.

Passive Operating On-chip Plasma Isolation From Whole Blood

In clinical chemistry, a necessary step performed is the isolation of plasma from whole blood, and effective sample preparation techniques are needed for the development of miniaturized clinical diagnostic devices. This study demonstrates the use of passive microfluidic devices, which operating entirely on capillary action, for on-chip isolation of plasma from whole blood. Using these devices, several to several tens nanoliter volumes of plasma were effectively separated from a single drop of whole blood in 2 minutes. This study may have broad implications in the design of lab-on-a-chip devices for bioanalytical applications.

Work of PZT ceramics sounder for sound source artificial larynx

We aim to develop the easy-to-use artificial larynx with high tone quality. We focus on using a PZT ceramics sounder as its sound source, because it is small size, low power consumption, and harmless to humans. But conventional PZT ceramics sounder have the problem that it cannot generate an enough sound in the low frequency range, thus they cannot be used for artificial larynx. Then, we aim to develop the PZT ceramics sounder which can generate enough volume in the low frequency range. If we can lower the resonance frequency of the sounder, it can generate low pitch sound easily. Therefore I created the new diaphragm with low resonance frequency. In addition, we could obtain the high amplitude by changing method of driving. This time, we report on the characteristic comparison of this new PZT ceramics sounder and conventional one. Furthermore, for this new one, we analyzed the best alignment of PZT ceramics and the shape of the diaphragm to obtain low resonance frequency and big amplitude. In fact we analyzed the optimization of the structure. The analysis is done by computer simulation of ANSYS and Laser Doppler Vibrometer. In the future, we will add intonation to the generated sound by input wave form which is developed concurrently, and implant the sounder inside of the body by the method of fixing metal to biomolecule which is done too. And so high tone quality and convenient artificial larynx will be completed.

The molecular adsorption-type endotoxin detection system using immobilized ε-polylysine

Hemodialysis for chronic renal failure is the most popular treatment method with artificial organs. However, hemodialysis patients must continue the treatment throughout their life, the results of long term extracorporeal dialysis, those patients develop the various complications and diseases, for example, dialysis amyloidosis etc. Dialysis amyloidosis is one of the refractory complications, and endotoxin is thought to be the most likely cause of it, recently. Endotoxin is one of the major cell wall components of gram-negative bacteria, and it has various biological activities. In addition, it is known that a mount of endotoxin exists in living environment, and medicine is often contaminated with endotoxin. When contaminated dialyzing fluids are used to hemodialysis, above-mentioned dialysis amyloidosis is developed. Therefore, it is important that the detection and removal of endotoxin from dialyzing fluids. Until now, the measurement methods using Limulus Amebosyte Lysate (LAL) reagent were carried out as the tests for the presence of endtoxin. However, these methods include several different varieties of measurement techniques. The following are examples of them, gelatinization method, turbidimetric assay method, colorimetric assay method and fluoroscopic method. However, these techniques needed 30-60 minutes for the measurement. From these facts, they are not able to use as a real-time endotoxin detector. The detection of endotoxin has needed to carry out immediately, for that reason, a new detection method is desired. In this research, we focused attention to adsorption reaction between ε-polylysine and endotoxin. ε-polylysine has the structure of straight chain molecule composed by 25-30 residues made by lysine, and it is used as an antimicrobial agent, moreover, cellulose beads with immobilized ε-polylysine is used as the barrier filter for endotoxin removal. The endotoxin is adsorbed to immobilized ε-polylysine, as the result of this reaction, the mass incrementation is occurred, and the existence of endtoxin can be detected immediately, by using of Quartz Crystal Microbalance (QCM). In this report, the immobilization of ε-polylysine onto the Au and Si substrate and its adsorptive activity are described. We use X-ray Photoelectron Spectroscopy (XPS) to confirm the ε-polylysine immobilization, and the adsorptive activity of immobilized ε-polylysine is measured by AFM and QCM. This molecular adsorption type endotoxin sensor aims to the realization of real-time endotoxin detection system.

Acoustic characteristics improvement of PZT ceramic sounder for sound source of artificial larynx

私達は修得が容易であり高音質な人工喉頭の開発を目標としている．その音源として，小型・低消費電力・人体に悪影響を与えない圧電スピーカーに着目した．しかし，従来の圧電スピーカーは低周波数域において十分な音を生成できないという問題点がある．そこで，低周波数域においても十分な音を生成することができる圧電スピーカーを開発することを研究の目的とする． 低周波数の音声を生成するために，圧電スピーカーの共振周波数を低くするという方法が考えられる．そこで，共振周波数の低い振動板を使用した圧電スピーカーの特性評価を行なった．その特性評価方法として，有限要素解析によるコンピュータシミュレーション，また，高速フーリエ変換による音響解析を行なった． コンピュータシミュレーションの結果から，振動板の剛性を調整すれば，その共振周波数を下げることができることが確認できた．そして，その振動板を用いた圧電スピーカから生成された音の音響解析の結果においても，共振周波数の低下を確認することができた．