Electrochemical Sensing of Dopamine with an Implantable Microelectrode Array Microprobe Including an On-Probe Iridium...

Area of Science:

• Neuroscience
• Biomedical Engineering
• Electrochemistry

Background:

• Monitoring dopamine (DA) signaling in vivo is crucial for understanding brain disorders such as Parkinson's disease and substance abuse.
• External reference electrodes (e.g., Ag/AgCl) can be unstable and induce inflammatory responses in vivo.
• Integrating a stable reference electrode directly onto the microelectrode array (MEA) is desirable for reliable neural recordings.

Purpose of the Study:

• To develop and evaluate an implantable microelectrode array (MEA) with an integrated on-probe iridium oxide (IrOx) reference electrode (RE) for sensitive and selective dopamine (DA) detection.
• To compare the performance of DA sensing using an on-probe IrOx RE in two- and three-electrode configurations against traditional external reference electrodes.
• To assess the selectivity of the integrated system against common electroactive interferents for in vivo applications.

Main Methods:

• Fabrication of a microprobe MEA featuring an integrated on-probe IrOx RE using electrochemical deposition.
• Testing of the integrated MEA in both two-electrode (working electrode [WE] and RE) and three-electrode (WE, RE, and counter electrode) configurations for DA sensing.
• Quantification of DA sensing sensitivity, limit of detection (LOD), and selectivity against interferents.

Main Results:

• Comparable DA sensing sensitivity (∼2500 nA/(μM·cm²) between integrated and external reference systems.
• The integrated three-electrode configuration achieved a 6-fold lower LOD (∼9 nM) for DA detection compared to external referencing.
• An 82% reduction in baseline noise was observed in the integrated three-electrode setup, contributing to the improved LOD.
• Demonstrated excellent selectivity (1000:1) against common electroactive interferents.

Conclusions:

• The on-probe IrOx RE integrated onto an MEA significantly enhances dopamine sensing performance, offering an ultralow LOD and high selectivity.
• This integrated system provides a stable and less inflammatory alternative to external reference electrodes for in vivo neuroscience research.
• The developed microprobe is highly suitable for precise in vivo monitoring of dopamine signaling in the context of neurological and psychiatric disorders.