A birefringent waveguide biosensor platform for label-free live cell detection of Listeria monocytogenes

We demonstrate a waveguide biosensor system integrated with a microfluidic channel, enabling label-free live cell detection of Listeria monocytogenes. It consists of a waveguide sensor platform to determine the immune reaction and a birefringence measurement system that measures the phase difference between two orthogonal polarizations, arising from the refractive index change of the immune reaction in the channel of the sensor platform. Fabrication of the waveguide sensor for this pathogen detection system is compatible with conventional integrated circuit processes. The waveguide platform is overlaid with TiO2 films of different thicknesses to optimize sensitivity. The implemented sensor was evaluated by L. monocytogenes detection. We experimentally confirmed a method for controlling the length of the TiO2 film to efficiently increase the detection sensitivity in our waveguide composition. We also demonstrated the proof of concept of our approach with a milk buffer to see similar detection results in a complex food matrix. We further tested the specificity of the L. monocytogenes detection platform with another pathogen, namely, Escherichia coli. The proposed system, which has a simple and compact composition, would be able to detect immune reactions for pathogenic bacteria, including L. monocytogenes as well as all other food poisoning bacteria