Novel Optical Biosensing System Using Mach–Zehnder-Type Optical Waveguide for Influenza Virus Detection

In order to minimize the damage from viral epidemics, early detection of the causative agent of a viral epidemic and prevention of its immediate spread are urgent social demands. Therefore, in this study, we evaluated the utility of a Mach–Zehnder-type optical waveguide as a sensing device for influenza virus detection. However, it is impossible to detect a 100-nm-size virus using a sol-gel optical biosensor because sol-gel glass has a pore size of only a few nanometers, which makes it impossible for the virus to diffuse into the silica thin film. In order to construct the influenza-specific Mach–Zehnder optical biosensor for influenza detection, a stable antibody immobilization method with resulting high density on the sol-gel surface is strongly required. In this study, the sol-gel glass surface was modified with amino and carboxyl groups, and an anti-H1N1/HA1 antibody was covalently immobilized using a cross-linking agent. We successfully prepared a carboxyl-modified sol-gel surface, using NHS/EDC as the cross-linker, for antibody immobilization, and confirmed the detection of influenza virus using the antibody-immobilized sol-gel glass. After treatment with a 100 μg/mL influenza virus solution for 15 min, a peak wavelength shift (~24 nm) was observed in the output light spectrum.