Feasibility of optical waveguide immunosensors for pesticide detection: physical aspects

The feasibility of detecting small molecules such as pesticides using optical evanescent-wave sensors is discussed with emphasis on the Mach-Zehnder sensor and a newly developed sensor called a ‘critical’ sensor. For direct detection of an estimated average pesticide layer growth of 2×10−4 nm, the sensitivity of the Mach-Zehnder sensor is almost adequate (1×10−3 nm within one hour), whereas that of the ‘critical’ sensor (2×10−2 nm) is not sufficient. However, the simplicity of this latter sensor is very attractive. Results of α-hSA/hSA immunoreaction experiments obtained with this last type of sensor are presented.