Nanomolecularly Imprinted Polymer Modified U-Bent Optical Fiber for Selective Detection of L -Tyrosine

Accurate detection of L-tyrosine is critical due to its significant role in regulating insulin and glucose metabolism, making it essential for effective diabetes management and related clinical diagnostics. To address this requirement, an optical fiber-based nano molecularly imprinted polymer (MIP) sensor specifically designed for the selective detection of L-tyrosine is developed. This sensor utilizes MIPs synthesized from pyrrole, with L-tyrosine serving as the template molecule. The nano-sized MIPs, characterized by dynamic light scattering (DLS) and scanning electron microscopy (SEM), exhibited a hydrodynamic diameter of 287 nm and uniform morphology. The optical sensing platform is constructed using a U-bent optical fiber with its core modified with 3-Aminopropyl) triethoxysilane (APTES) to enhance its sensitivity by functionalizing the optical fiber surface with amine groups, which improve the adhesion and uniformity of the MIP layer. The MIP layer is applied through an optimized dipping process, achieving the thickness with a 1-hour dipping time, and demonstrated stability for 15 days. With a repeatability of 4 washes. Evaluated using UV-VIS spectrophotometry, the sensor showed high selectivity for L-tyrosine over other analytes, such as dopamine, uric acid, glucose, and creatinine. It exhibited a linear range of 1 μM to 300 μM and a Limit of detection (LOD) of 0.36 μM with strong correlation coefficients (R² = 0.99). This novel in situ MIP-based optical sensor offers a robust, sensitive, and specific tool for clinical diagnostics, food safety monitoring, and environmental analysis. The developed device is finally tested on a portable μSens optical device as well as real-time analysis on human blood and serum samples.