Vol.3 No.1 2010

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Research paper : Biomarker analysis on microchips (M. Kataoka et al.)−44−Synthesiology - English edition Vol.3 No.1 (2010) require immediate diagnosis, particularly in acute diseases and infections, such as cardiac infarction, influenza diagnostic kit, blood glucose measurement, as well as blood gas measurements in the operating room. However, these products target biomarkers only of specific diseases, and have problems since many detection methods are qualitative. The development a POCT device that can solve these current problems and quantitatively analyze multiple biomarkers will be a core technology for a personal-level multiple biomarker monitoring in the future. Only when the POCT technology is established and its efficacy is recognized in clinical practice, the personal health monitoring technology will be recognized by society (Fig. 2). To do so, it is necessary to realize the POCT device that allows quantitative analysis of multiple biomarkers as soon as possible. Due to the advances in recent analysis technology using nanotechnology, high speed, smaller sample, and higher sensitivity are achieved in testing, as well as the downsizing of device. The development of a device using various microchips is a typical topic of such technological development. Such a device provides benefits to POCT, as explained in the following chapter, and as a personal-level biomarker device. Therefore, as a step for achieving the above goal, we present the application of the nano biodevice to the development of the POCT device by combining the existing microchip core technologies such as the glucose analysis using the commercially-available microchip electrophoresis device for nucleic acid analysis, and the construction of the antigen-antibody reaction system on the micro flow channel using microfluidics. The issues that are yet to be solved will be described from the standpoint of a biological user with clinical experiences.2 Requirements of the POCT deviceThe POCT device must allow measurement of a biomarker quickly in the doctor’s office or the hospital ward, provide analysis within 30 min[1], possess sensitivity and reproducibility usable for clinical diagnosis, enable measurement equivalent or superior to the current clinical test method, have compactness that enables installation in the office, and be operable for physicians while interviewing patients. Regular blood tests require several ml of blood per test item, and that is not only stressful to the patients, but also is costly since it necessitates large quantities of reagents for the test tube analysis. Therefore, analysis with microscale samples is in demand not only in POCT but also in clinical tests in general. Also, since the test samples include blood, the device material must be easily sterilized after testing. Also, considering the needs of a device that allows the detection of multiple test items, we focused on the microchemical chip technology based on the microfabrication technology, or the microchemical analysis system where the procedures for chemical and biochemical analyses such as the pretreatment, separation, reaction, and detection are integrated on a microchip of few centimeter square size. Aiming at the application to the POCT device, we clarified the conditions for optimal detection of commercially-available individual biomarkers using the microchip electrophoresis and microfluidics, and worked on the on-chip mounting of the biomarker detection system.3 Application of the microchip substrate to the POCT device3.1 Construction of the biomarker measurement method using the glucose analysis by microchip electrophoresis3.1.1 Application of the microchip electrophoresis to biological and biochemical analysisMicrochip electrophoresis devices have been developed and are commercially available. In these devices, electrophoresis is conducted in the micro flow channel with µm-level width and depth formed on the microchip made of plastic or glass material of a few centimeter square size using the microfabrication technology for semiconductors. Compared to the conventional electrophoresis method for the separation analysis of nucleic acid and proteins, the microchip electrophoresis has high separation capacity by application of high voltage, because the sample volume can be reduced by using the micro flow channel, and because the efficiency of heat release during electrophoresis is increased due to the increased surface volume against the sample volume in the flow channel. Moreover, higher sensitivity can be achieved by using the LED-excited fluorescence detection system. These devices, however, are not sufficiently diffused in the biology and biochemistry labs of the universities that are expected to be the main users. The main reasons are because their usage is limited to the separation analysis of nucleic acids, the price of the electrophoresis device is higher compared to the conventional agarose electrophoresis, and the cost of microchips and gel necessary for the analysis per sample is about 200 times higher. Therefore, we attempted using the device for purposes other than nucleic acid separation without changing the electrophoresis chip, the device, or ResultBloodClinical testDiagnosisMarker informationDatabaseMultiple biomarkerdetection technologyPOCTVisit to hospitalClinical testMultiple biomarkerdetection at homeFig. 2 Requirements for POCT and the schematic diagram of the integrated microchip substrate.The plasma separation mechanism is installed onto the microchip substrate. There are flow channels for microchip electrophoresis and microfluidics system.

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