Enhanced electrochemical sensor sensitivity by using molecular imprinting techniques for the detection of dopamine

This study investigates a molecularly imprinted electrochemical sensor for sensitive dopamine (DA) determination. The purpose of this work is to develop high- performance and miniaturizable sensors for DA, a neurotransmitter (NT) involved in many neurological diseases. The concentration of NTs in the human body is extremely low and, for this reason, the sensor utilized for their detection should have physiologically relevant sensitivity. Molecular imprinting consists in the formation of a polymeric layer modified with recognition sites to a particular target analyte. This is carried out through the polymerization of the functional monomer in the presence of the target. The electrodes developed in this study are based on a silicon substrate, modified with a tetraheadral amorphous carbon (ta-C) layer and a DA imprinted polypyrrole (PPy) layer. The molecular imprinting of pyrrole was carried out electrochemically through cyclic voltammetry (CV) in presence of DA. The ta-C layer has been involved in order to further improve the performance of the electrode, as it provides extremely interesting properties. The proposed MIP-based sensors have been studied electrochemically by CV, differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) and they showed an enhanced performance with respect to their non-imprinted counterpart. The limit of detection (LOD) was measured to be in the nanomolar range (48.6 nM), which ensures a physiologically relevant sensitivity (162 nM). At first, the experimental conditions for molecular imprinting were optimized in order to improve the performance of the electrodes. Electrochemical and physical (SEM, AFM, Raman spectroscopy) characterizations have been carried out in order to better understand the behaviour of the sample in the sensing system. The performance of the designed MIP/ta-C electrodes toward DA has been studied at different DA concentrations and in the presence of interferents. At last, the effect of the thickness of the ta-C layer and of the presence of a titanium adhesion layer have been considered. The current work has been carried out at the Department of Electrical Engineering and Automation at Aalto University (Espoo, FI). In particular, the facilities in which the studies have mainly taken place are at Micronova, Finland’s national research infrastructure for micro- and nanotechnology.