Continuous Real-Time Detection of Serotonin using Aptamer-Based Electrochemical Biosensor

Serotonin (5-HT) is a critical neurotransmitter involved in many neuronal functions, and 5-HT depletion has been linked to several mental diseases. The fast release and clearance of serotonin in the extracellular space, low analyte concentrations and a multitude of interfering species make detection of serotonin challenging. This work presents an electrochemical aptamer-based biosensing platform that can monitor 5-HT continuously with high sensitivity and selectivity. Our electrochemical sensor showed a response time of approximately 1 minute to a step change in the serotonin concentration (from 0 to 25 nM) in continuous monitoring using single frequency EIS (electrochemical impedance spectroscopy) technique. The developed sensing platform was able to detect 5-HT in the range 25 nM – 100 nM in the continuous sample fluid flow. The electrochemical sensor showed promising selectivity against other species with similar chemical structures and redox potentials including dopamine (DA), norepinephrine (NE), L-tryptophan (L-TP), 5-hydroxyindoleacetic acid (5-HIAA), and 5-hydroxytryptophan (5-HTP). The proposed sensing platform is able to achieve time resolution on the order of a minute with high selectivity in the nanomolar range demonstrating a potential for monitoring serotonin from neurons in organ-on-a-chip or brain-on-a-chip-based platforms.