An integrated metal clad leaky waveguide sensor for detection of bacteria

An integrated optical metal clad leaky waveguide (MCLW) sensor device has been developed for the detection of bacteria. This is more sensitive than waveguide sensors currently in use. The MCLW device has been fabricated to extend the evanescent field to provide significant light intensity over the entire volume of the bacteria bound on the chip surface within this field. This in turn increases the interaction of the light with the entire volume of the bacteria. MCLW devices have been used for detecting refractive index changes, scattering, and fluorescence from bacterial spores captured on an immobilized antibody. The detection limit of Bacillus subtilis var. niger bacterial spores using refractive index detection was 8 x10(4) spores/mL. The scattering intensity of the BG spores was found to be three times greater than the scattering intensity generated using surface plasmon resonance. The extended light propagation along the direction of flow for a few millimeters provides an effective interrogation approach to increase the area of detection to detect low concentrations down to 1 x 10(4) spores/mL. The sensor was then optimized by studying the key factors affecting sensor performance including changing the pH of the medium, type of antibody immobilization matrix, sensor surface regeneration approaches, and longevity of the sensor.