Vol.8 No.2 2015

Research paper : Detection of influenza viruses with the waveguide mode sensor (K. AWAZU et al.)−99−Synthesiology - English edition Vol.8 No.2 (2015) skilled clinical lab technicians and 43.8 % for lab personnel. Baccam et al. reported that the A/Hong Kong/123/77H1N1 strain sampled by nose smear reached the maximum value in two to three days after infection, and the value was about 5 × 102-1 × 103 TCID 50/mL nasal wash.[13] Considering the above three studies, it can be seen that the detection with good precision cannot be obtained by immuno-chromatography unless the virus count reached the maximum after infection.According to the National Institute of Infectious Diseases, the false positive (true negative) by immuno-chromatography method is seen most frequently in the early stages of an outbreak when the influenza is not yet common in the community, as well as in the final stages.[14] Also, the false negative (true positive) by immuno-chromatography is seen commonly during an outbreak when the influenza is rampant in the community.The situation is similar for avian flu, and the Ministry of Environment reported that the problem of immuno-chromatography was that infected birds might show negative.[15] For example, the manual presents a case where of the 60 birds that were positive in the definitive test, only 27 were tested positive in the simplified test. Conversely, there were cases where the birds were positive in the simplified test but negative in the definitive test. As a reason, it is explained that the virus in the sample became inactive due to drying or not being kept in low temperature during the period when the virus was taken to the lab and became subject to the definitive test of virus isolation. This means a technology for highly sensitive and quick detection at several digits higher than the current method is needed.3 Developed content3.1 Development of portable waveguide mode sensorWe have been developing our original waveguide mode sensors.[16][17] As reported in Synthesiology,[1] in the earliest waveguide mode sensor, the waveguide modes were formed in the reflective film layer and the waveguide layer at a certain angle of incidence. When the angle sweep is done using the He-Ne laser at a wavelength of 632.8 nm as the light source, the reflection intensity declines at a certain angle. When the surface condition changes such as by the adsorption of molecules on the surface, it is possible to measure the accompanying changes in the refraction index of the surface. However, in this case, it was necessary to conduct the sweep by synchronizing the two goniometers on the light source and detector sides as shown in the optical system in Fig. 1, and there was a problem that the optical system itself became large and complex. Therefore, we thought perhaps we could not satisfy the user demand for a potable sensor using the angle sweep type. Rather than sweeping the angle, we devised a method for sweeping the wavelength. If a spectrum is obtained by sweeping the wavelength, it would be possible to discard the two goniometers that were barriers to size reduction.[18] Figure 2 shows the simulation results of reflectivity changes before and after adsorption, assuming the adsorption of protein with 5 nm diameter (refractive index 1.45). The calculation was done with monocrystalline silicon layer thickness of 220 nm, silica waveguide layer thickness of 360 nm, prism material of silica, and at s-polarization. Several peaks were observed. For example, there was a peak in the range where the reflectivity change reached maximum at around 500 nm and 68º. From this calculation result, it was found that the target substance could be detected by fixing the angle of incidence and observing the reflection spectrum of the incoming light.Fig. 1 (a) Optical arrangement of the angle sweeping waveguide mode sensor. Monocrystalline silicon (c-Si) film was laminated onto a SiO2 glass substrate beneath the prism. The c-Si was thermally oxidized to form an amorphous SiO2 (a-Si) film, and waveguide modes were formed inside this SiO2 film. The reflection intensity was observed to change rapidly at a certain angle 2. When the molecule adhered to the amorphous silica surface, the value of 2 changed. The angle 2 synchronized the two goniometers.(b) Conceptual image of the molecules adsorbing onto the amorphous silica surface in the optical system (a). The horizontal axis became 2. is before the molecules were adsorbed and is after they were adsorbed.(b)(a)Amorphous silicaPrismLight sourceDetectorPolarizerSilicon0. of incidence7271706968


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