A Flexible Carbon Nanofiber-Modified Multi-Channel Electrode Enables High-Sensitivity Electrochemical Detection of Multiple Neuroactive Molecules.

Electrochemical detection is widely acknowledged as a promising technique for quantifying neuroactive molecules, credited to its low cost, portable hardware, and distinctive ability to enable in vivo real-time dynamic monitoring. However, key hurdles still block the technology's standardization, commercial clinical translation, and on-site application, including poor biocompatibility at the sensing interface, inadequate mechanical stability, and restricted detection generality. To address these drawbacks, this work introduces a multi-channel flexible microwire electrode array. Here, carbon-based nanomaterials build a high-conductivity internal backbone and an analyte-concentrating sensing surface, while chitosan (CS) supports film formation and boosts biocompatibility. These two composite film layers were modified onto the gold surface of MEMS-fabricated flexible microelectrodes via electrophoretic deposition. At optimized voltage and deposition duration, the carbon nanofiber (CNF)-modified electrode outperformed both nitrogen-doped reduced graphene oxide (NGO) electrodes and unmodified gold electrodes. It delivered strong, well-resolved responses for tyrosine, tryptophan, norepinephrine, melatonin, and tryptamine, with detection limits of 9, 45, 50, 15, and 20 μM, respectively, alongside high reproducibility and promising initial stability. Capitalizing on the CS/CNF-Au electrode's excellent mechanical and electrical performance, this study verifies that tuned carbon-based composite layers enable high-performance electrochemical interfaces, offering a new route to develop flexible universal detection platforms that integrate both biocompatibility and structural reliability.