LAUSR

Abstract A label-free fiber optic biosensor based on single mode-tapered multimode-single mode (SMS) structure for bacteria detection has been reported. The main aim of the present study was the sensitive detection of Salmonella Typhimurium in phosphate buffer saline (PBS) and spiked samples of milk. The multimode interference based SMS sensor was developed for biosensing application by removal of cladding region of the multimode fiber, followed by modification of the etched region with anti-S. Typhimurium monoclonal antibodies. The antibodies functionalized SMS biosensor provided S. Typhimurium detection in a wide linear range (500 CFU/mL − 5000 CFU/mL) to attain limit of detection (LOD) of 247 CFU/mL. The complete analysis process for each sample including regeneration was completed in less than 20 min. A comprehensive theoretical study of the developed biosensor regarding beam propagation and power distribution has been presented. The developed biosensor showed high selectivity in the presence of Escherichia coli and Staphylococcus aureus. It provides an alternative platform for rapid and specific detection of S. Typhimurium without any prior sampling processes. The proposed biosensing technique could be used for sensitive detection (275.86 nm/RIU) of the broad spectrum of pathogens.