Simple leaky-waveguide devices for the detection of bacterial spores

A variety of biocompatible optical leaky waveguide sensors were developed for bacterial detection. Divalent sensitive polymer waveguides incorporating the chelating agent nitrilotriacetic acid (NTA) were used to monitor the release of Ca2+ ions from Bacillus subtilis spores during the first stage of germination. Co-polymer waveguides incorporating hydrolyzed starch were used to detect the presence of exo-enzymes released during the later stages of vegetative growth. The limit of detection for calcium, based on changes in the intensity of the TE0 mode was 60 μM. Changes in refractive index were demonstrated by measuring the change in the angular position of the TE1 mode resulting from the degradation of the waveguide by α-amylase.