Porous Carbon Nanofiber-Modified Carbon Fiber Microelectrodes for Dopamine Detection

We present a method to modify carbon fiber microelectrodes (CFME) with porous carbon nanofibers (PCFs) to improve detection and to investigate the impact of porous geometry for dopamine detection with fast-scan cyclic voltammetry (FSCV). PCFs were fabricated by electrospinning, carbonizing, and pyrolyzing poly­(acrylonitrile)-b-poly­(methyl methacrylate) (PAN-b-PMMA) block copolymer nanofiber frameworks. Commonly, porous nanofibers are used for energy storage applications, but we present an application of these materials for biosensing, which has not been previously studied. This modification impacted the topology and enhanced redox cycling at the surface. PCF modifications increased the oxidative current for dopamine (2.0 ± 0.1)-fold (n = 33) with significant increases in detection sensitivity. PCFs are known to have more edge plane sites which we speculate lead to the 2-fold increase in electroactive surface area. Capacitive current changes were negligible, providing evidence that improvements in detection are due to faradaic processes at the electrode. The ΔE_p for dopamine decreased significantly at modified CFMEs. Only a 2.2 ± 2.2% change in dopamine current was observed after repeated measurements and only 10.5 ± 2.8% after 4 h, demonstrating the stability of the modification over time. We show significant improvements in norepinephrine, ascorbic acid, adenosine, serotonin, and hydrogen peroxide detection. Lastly, we demonstrate that the modified electrodes can detect endogenous, unstimulated release of dopamine in living slices of rat striatum. Overall, we provide evidence that porous nanostructures significantly improve neurochemical detection with FSCV and echo the necessity for investigating the extent to which geometry impacts electrochemical detection.