Enzyme‐Mediated Sulfhydryl Exposure‐Induced Etching Suppression of Gold Nanostars for Biosensing

ABSTRACT

Cholinesterase (ChE) is an important biomarker for organophosphate pesticide poisoning, liver function, and Alzheimer's disease. However, current methods are limited by poor matrix tolerance, insufficient portability, and unstable enzyme activity for their application in point‐of‐care detection. Plasmonic biosensors have emerged as innovative analytical tools for the colorimetric sensing of biomarkers. Herein, we report an enzyme‐mediated sulfhydryl exposure‐induced etching suppression of gold nanostars for colorimetric detection of ChE activity. Sulfhydryl‐containing molecules (─SH) prevent the iodide‐mediated surface etching surface of gold nanostars by forming stable Au─S bonds. The presence of acetylcholinesterase (AChE) can hydrolyze acetylthiocholine to produce acetate and sulfhydryl‐containing thiocholine, thus suppressing the surface etching of gold nanostars. By combining the AChE–catalyzed sulfhydryl exposure with sulfhydryl‐mediated etching suppression, this strategy enables to quantitatively detect AChE activity in the range of 1.2 mU/L to 12 kU/L with a LOD of 0.129 mU/L by monitoring localized surface plasmon resonance (LSPR) shifts of gold nanostars. Additionally, it enables the screening of AChE inhibitors and reactivators. The biosensing strategy developed in this work presents a novel plasmonic approach that holds significant potential as a point‐of‐care platform for clinical diagnosis, food safety, and environmental monitoring.