Electroenzymatic choline sensing at near the theoretical performance limit

Area of Science:

• Biosensor Technology
• Neuroscience
• Electrochemistry

Background:

• Electroenzymatic sensors are crucial for monitoring neurochemicals like choline, a surrogate for acetylcholine, in vivo.
• Existing sensors often lack the sensitivity and response speed required for real-time neurotransmitter signaling studies.
• Mathematical modeling can guide the optimization of microsensor design for improved performance.

Purpose of the Study:

• To create a high-performance electroenzymatic microsensor for choline with sensitivity approaching theoretical limits.
• To improve sensor response time for better resolution of transient neurochemical signals.
• To enable denser microelectrode array (MEA) probe designs for cellular-level spatial resolution.

Main Methods:

• Immobilization of choline oxidase (ChOx) on platinum-coated electrodes.
• Coating electrodes with permselective polymer layers (poly(m-phenylenediamine) and Nafion).
• Optimization of ChOx layer thickness and polymer film thickness guided by mathematical modeling.
• Characterization of sensor sensitivity, response time, and selectivity at 37 °C.

Main Results:

• Developed a choline microsensor exhibiting unprecedented sensitivity (660 ± 40 nA μM⁻¹ cm⁻²) and rapid response time (0.36 ± 0.05 s).
• Achieved excellent selectivity, crucial for accurate in vivo measurements.
• Optimized sensor design involved a ∼5 μm ChOx layer and 200 nm permselective films.

Conclusions:

• The developed electroenzymatic choline microsensor significantly enhances sensitivity and response time.
• This advancement facilitates the design of denser MEA probes for high-resolution in vivo neurochemical monitoring.
• Improved sensor performance will advance the study of brain function by enabling better correlation of neurochemical signals with electrophysiology.