Localized Plasmon-Based Multicore Fiber Biosensor for Acetylcholine Detection

Abstract

In this work, tapered/etched multicore fiber (MCF) probes are spliced with multimode fiber (MMF) to fabricate the sensor structure. To improve sensitivity, gold nanoparticles (AuNPs) and molybdenum disulfide nanoparticles (MoS ₂ -NPs) are used to immobilize both probes. Synthesized AuNPs and molybdenum disulfide (MoS ₂ )-nanoparticles (NPs) have peak absorption wavelengths of 519 and 330 nm, respectively. High-resolution transmission electron microscopy is used to examine the morphology of the NPs. The scanning electron microscope (SEM) is used to characterize the NP-immobilized optical fiber sensor structures, and SEM-EDX is used to verify the NP-coating over fiber structure. The functionalization of the acetylcholinesterase enzyme over the NP-immobilized probe increases the specificity of the sensor later on. Finally, the developed sensor probes are tested by detecting various acetylcholine concentrations. In addition, performance analyses, such as reusability, reproducibility, and selectivity (in the presence of ascorbic acid, glucose, dopamine, and uric acid), are carried out, and proposed biosensors are experimentally evaluated. The developed tapered fiber sensor with a sensitivity of 0.062 nm/ $\mu \text{M}$ can detect even very low concentrations, such as 14.28 $\mu \text{M}$ , over a wide detection range of 0–1000 $\mu \text{M}$ .