Electrochemical activities of Fe2O3-modified microelectrode for dopamine detection using fast-scan cyclic voltammetry

Dopamine (DA) is the most important neurotransmitter involved in motor control. Abnormalities in neurotransmitter levels may indicate brain disorders, such as Parkinson’s disease and depression. Herein, electrochemical sensors containing metal oxide nanoparticles were fabricated for detecting DA. Specifically, iron oxide nanoparticles were applied onto a flexible polyimide substrate to obtain a flexible microelectrode and their DA detection performance was evaluated in vitro and in vivo. The electrochemical performance of the fabricated sensor was evaluated via fast-scan cyclic voltammetry conducted in a DA solution at concentrations between 0 and 50 nM. The peak current corresponding to the oxidation reaction of the Fe2O3-modified microelectrode for DA was observed at an applied potential of 0.49 V. The modified microelectrode exhibited a DA response with a high sensitivity of 34.14 nA/μm2 nM and a low limit of detection of 8.76 nM. In vivo experiments were performed using a freely moving mouse. Notably, 15 min after nicotine injection, the current increased considerably. The peak current corresponded to a 10 nM concentration in the calibration curve. The co-detection of DA and serotonin was also analyzed. The results showed that only the oxidation peak of DA appeared upon applying a triangular voltage waveform. Therefore, the proposed detector is capable of overcoming the drawbacks associated with conventional detectors and can be integrated with other implantable devices.