Real-time interrogation of fiber optic biosensor using TiO₂ coated etched long-period grating

In this work, a TiO₂ coated etched long-period grating (e-LPG) fiber optic biosensor is developed for the detection of Escherichia coli (E. coli) bacteria in food items. Label-free Escherichia coli bacteria monitoring is done over the detection range of 0 cfu/ml-50 cfu/ml using an advanced spectral interrogation mechanism. The thin film deposition of 40 nm TiO₂ over the e-LPG is confirmed by the microscopy method, such as scanning electron microscopy. In our proposed biosensor design, T4-bacteriophage is covalently immobilized over the TiO₂ coated fiber surface. This biosensor system has reached sensitivity at 2.55 nm/RIU. Our experiments confirm the resolution and the limit of detection (3σ/S) of 0.0039 RIU and 10.05 ppm, respectively. The proposed biosensor with enhanced sensitivity is suitable for monitoring harmful pathogens/infectious agents in various food products.