Vol.8 No.2 2015
Research paper : Detection of influenza viruses with the waveguide mode sensor (K. AWAZU et al.)−103−Synthesiology - English edition Vol.8 No.2 (2015) From the results of the above quantitative tests, it was found that the waveguide mode sensor was one to two digits higher in sensitivity compared to the immuno-chromatography and direct adsorption ELISA methods. The Sandwich ELISA method was troublesome to conduct since the preliminary treatment was complicated and the procedure took several hours to a day until detection, and also it depended on the skill of the testing personnel. Therefore, the waveguide mode sensor technology is thought to have overwhelming superiority over other methods in terms of simplicity of preliminary treatment and time required.3.3 Nonspecific adsorption inhibiting surfaceThe important point in the detection by antigen-antibody reaction is to prevent nonspecific adsorption. Surface formation as shown in Fig. 11 was created in a joint research with the Biomedical Research Institute, AIST. Methoxyoligoethyleneglycol-triethoxysilane was used as the modifying material for the silane surface to inhibit nonspecific adsorption of protein. This is an oligoethyleneglycol group where the terminal has been methylated, and it is capable of almost completely inhibiting nonspecific adsorption. Succinimide ester-triethoxysilane was used as the silane surface modifying material to fix the antibodies. The succinimide group was present on the surface terminal to which the antibodies were fixed. By soaking the detection plates with these silica surfaces in two types of hybrid solutions, a high level blocking property and an antibody fixing property were achieved. Currently, it has been confirmed that nonspecific adsorption could be efficiently inhibited in the detection of viruses in serum and plasma. It is expected to specifically detect influenza viruses in nose smear samples.3.4 Synthesiological discussionFigure 12 shows the synthesiological description of the above process. The “realization of a simple and highly sensitive influenza virus detector” is the demand and the goal. On the other hand, we already have significant accumulation of elemental technologies of silicon technology, optics, and electromagnetics. To achieve an integrated technology, the fusion of the four fields of elemental technologies, where there were hardly any overlaps, was necessary. By conducting Wavelength (nm)Wavelength (nm)5005060708090100Reflectivity (%)(b)(a)2,6-sialic acid coated gold nanoparticles2,3-sialic acid coated gold nanoparticlesantibodyH3N2520540560580600H3N2500520540560580600Reflectivity (%)708090100(c)(d)H3N2(b)2,6-sialic acid coated gold nanoparticles(a)H5N1HA(d)Reflectivity (%)Wavelength (nm)Wavelength (nm)(c)5605405205006070809010060708090100560530550510540520500Reflectivity (%)2,3-sialic acid coated gold nanoparticlesFig. 9 The H3N2 virus was fixed on the waveguide mode detection plate using antibodies. The gold nanoparticles with diameter of 5 nm were coated with 2,6-sialic acid and 2,3-sialic acid, and were used as labels. High sensitivity was achieved by using such gold nanoparticles. (a) The 2,6-sialic acid on gold nanoparticle surface bonded with the HA protein of H3N2. (b) The 2,3-sialic acid on gold nanoparticle surface did not bond with the HA protein of H3N2. When the reactions of (a) and (b) were actually observed using the waveguide mode sensor, (c) the 2,6-sialic acid on gold nanoparticle surface bonded with the HA protein of H3N2 and the spectrum changed (from black line to red line). (d) The 2,3-sialic acid on gold nanoparticle surface did not bond with the HA protein of H3N2 and the spectrum did not change.Fig. 10 The H5N1 HA was fixed using antibodies. The gold nanoparticles with diameter of 5 nm were coated with 2,6-sialic acid and 2,3-sialic acid, and were used as labels. (a) The 2,6-sialic acid on gold nanoparticle surface did not bond with the H5N1. (b) The 2,3-sialic acid on gold nanoparticle surface bonded with the H5N1. When the reactions of (a) and (b) were actually observed using the waveguide mode sensor, (c) the 2,6-sialic acid on gold nanoparticle surface did not bond with the H5N1 and the spectrum did not change. (d) The 2,3-sialic acid on gold nanoparticle surface bonded with the H5N1 and the spectrum changed (from red line to brown line).