Partially Functional Electrode Modifications for Rapid Detection of Dopamine in Urine

Designing functional materials as electrode coatings to transduce high-quality information about redox molecules in biofluids is crucial for developing the next-generation medical devices. Rapidly analyzing the neurotransmitter dopamine (DA) urinary levels can enable point-of-care testing for neuroendocrine tumors. A novel sensing electrodes array modified with biopolymer chitosan and electrocatalytic carbon nanotube films that can generate cross-reactive electrochemical signals from complex biofluids, such as undiluted urine, is presented. By generating cross-reactive signals, the feasibility of quantifying DA levels from unprocessed urine samples is demonstrated. The films' electrochemical activity is characterized and modeled the additive effect of the main redox interferants in urine (norepinephrine and uric acid) on the generated electrochemical signals that overlap and mask the electrochemical signature of DA. Finally, the feasibility of successfully quantifying urinary DA levels is demonstrated by investigating two calibration approaches: 1) using a synthetic solution (1.15 mu m root mean squared error (RMSE) and 4.2 mu m limit-of-detection (LoD) values), and 2) directly using the urine samples (2.5 mu m RMSE and 9.3 mu m LoD values). The outcome of this work will enhance the understanding of the overlapping and masking electrochemical signatures and their interactions with functional materials, providing better analytical tools to differentiate redox molecules in highly complex biofluids.