A New Acetylcholine Optical Fiber Biosensor Based on Gold Film-GNRs Resonance Coupling Enhancement

An enhanced resonance coupling of gold film-gold nanorods (GNRs) based optical fiber acetylcholine (Ach) biosensor was fabricated with increased sensitivity for refractive index (RI) sensing. Gold film with a thickness of about 50 nm is sputtered on the surface of the optical fiber by the magnetron sputtering, and then the GNRs synthesized by seed-mediated were immobilized on the surface of the gold film by using 1,6-hexodithiol as a crosslinker via cross-link method. The RI sensitivities (SRI) improvement rate of the sensors was 24.09% higher than that of the sensor without GNRs functionalization. Acetylcholinesterase (AchE), as the specific recognition substance of the biosensor, was immobilized on the surface of GNRs by the chemical crosslinking method to prepare optical fiber sensing probes. Under the optimum preparation conditions of the optical fiber sensing probe, the wavelength shift of the surface Plasmon resonance (SPR) peak has a good linear relationship with the concentration of Ach (CAch) in the range of 0.5–
$5 \mu \text{g}$
/mL with the sensitivity of 0.4912 nm/(
$\mu \text{g}$
/mL) and limit of detection (LOD) was
$0.45 \mu \text{g}$
/mL. In addition, the optical fiber biosensor has good stability and selectivity, which makes it have broad application prospects in the early diagnosis of degenerative disease.