FAST (Flexible Acetylcholine Sensing Thread): Real-Time Detection of Acetylcholine with a Flexible Solid-Contact Potentiometric Sensor

Abstract

Acetylcholine (ACh) is involved in memory and learning and has implications in neurodegenerative diseases; it is therefore important to study the dynamics of ACh in the brain. This work creates a flexible solid-contact potentiometric sensor for in vitro and in vivo recording of ACh in the brain and tissue homogenate. We fabricate this sensor using a 250 μm diameter cotton yarn coated with a flexible conductive ink and an ACh sensing membrane that contains a calix[4]arene ionophore. The exposed ion-to-electron transducer was sealed with a 2.5 μm thick Parylene C coating to maintain the flexibility of the sensor. The resulting diameter of the flexible ACh sensing thread (FAST) was 400 μm. The FAST showed a linear response range from 1.0 μM to 10.0 mM in deionized water, with a near-Nernstian slope of 56.11 mV/decade and a limit of detection of 2.6 μM. In artificial cerebrospinal fluid, the limit of detection increased to 20 μM due to the background signal of ionic content of the cerebrospinal fluid. The FAST showed a signal stability of 226 μV/h over 24 h. We show that FAST can measure ACh dynamics in sheep brain tissue and sheep brain homogenate after ACh spiking. FAST is the first flexible electrochemical sensor for monitoring ACh dynamics in the brain.

Review—Electrochemical Sensors for Acetylcholine Detection

“…where K I is an experimentally determined constant potential value and a I is the primary ion activity. If interfering ions are introduced for ACh detection, the well-established Nikolsky-Eisenman equation would be more appropriate, 143 ( )…”

“…6 A. 145 Amirghasemi et al in 2023 143 developed a flexible solid-contact potentiometric sensor enriched with a calix [4]arene ionophore for ACh concentration detection in the brain. The sensor demonstrated impressive linearity and a low limit of detection (LOD) in HEPES buffer pH 4.0, although the LOD increased when tested in artificial cerebrospinal fluid due to background signals.…”

Recent advances in nanomaterial-based solid-contact ion-selective electrodes

“…4 shows the main steps for preparing the TMA sensor, its morphological image, as well as photos of the portable sensing device. Carbon black has also been used as a solid contact in SC-ISEs for the determination of Na + , K + , NO 3 − , and acetylcholine, 103–108 exhibiting a Nernstian response with low LODs.…”