Ultra-sensitive fiber optic LSPR biosensor with enhanced enzyme functionalization for real-time putrescine detection

Putrescine is a kind of physical diamine that is closely related to food deterioration and food quality safety. This study employs a novel fiber optic biosensor based on S-tapered and waist extension techniques, as well as localized surface plasmon resonance (LSPR), to detect putrescine accurately. The gold nanoparticles (AuNPs) are fixed on the fiber to excite LSPR. Furthermore, the multi-walled carbon nanotubes (MWCNTs) and niobium carbide (Nb2CTx) are used to increase the binding sites of enzymes to improve the sensing performance of probes. In this work, the fiber probe surface is functionalized by diamine oxidase (DAO) to improve selectivity. The sensitivity and limit of detection of the fiber optic biosensor are 2.04 nm/lg(µM) and 0.267 µM over a linear range of 0-100 µM, respectively. In addition, the tests of repeatability, reusability, selectivity, pH value, and real samples of the sensor probe are assessed to demonstrate the potential in measuring putrescine. © 2025 Optica Publishing Group (formerly OSA). All rights reserved.