Biomimetic Coatings on Thin-Film Electrodes for Neurotransmitter Sensing Applications

Achieving real-time monitoring of neurotransmitters enables one to monitor cognitive performance, diagnose mental health issues, and build the correlation between neurotransmitters and cognitive state. A subset of neurotransmitters, monoamine neurotransmitters (e.g. dopamine, serotonin, epinephrine), are commonly targeted for electrochemical biosensors, as they are inherently redox active, and thus can be detected directly by an electrical pulse. However, sensitivity and selectivity remain key challenges towards the fabrication and deployment of these sensors in wearable platforms. Au and Carbon-based electrodes have previously shown to be highly effective electrode materials as they are both biocompatible and easily modified for sensor fabrication. However, the current state-of-the-art form of the aforementioned electrodes show poor resolution at low analyte concentrations. Here we show multiple strategies to enhance the sensing capabilities for the Au and Carbon-based surfaces which have been specifically tailored to directly target neurotransmitters such as Serotonin and Dopamine. We demonstrate that electrodeposited PSS (polystyrene sulfonate) alone, likely due to its negative charge and aromatic structure, has improved sensitivity compared to the previously tested PEDOT:PSS (3,4-ethylenedioxythiphene polystyrene sulfonate). We have electrodeposited various thicknesses of pure PSS atop of a Carbon-based electrode sensor allowing us to detect Serotonin concentrations as low as 10 nM, well below the physiological levels in both the blood and Interstitial fluid (ISF). Furthermore we show two specifically designed peptides with enhanced sp₂ stacking which regain selectivity to Serotonin with a detection limit as low as 10-20 nM, mimicking the hybridization observed on graphene/carbon electrodes with an exceeding sensitivity.