Selective detection of dopamine in urine with electrodes modified by gold nanodendrite and anionic self-assembled monolayer

The determination of dopamine (DA) in urine is a promising technique for non-invasive DA monitoring, but current electrochemical techniques face substantial interference from uric acid (UA). This study applies three-dimensional gold nanodendrite (Au-DT) and self-assembled monolayer (SAM) to modify gold electrodes to improve their sensitivity and specificity to DA and alleviate UA interference. With the optimal ω-mercaptoalkane carboxylic acid chain length, the differential pulse voltammograms of Au-DT deposited electrode coated with 8-mercaptooctanoic acid (MOA) exhibit two voltammetric peaks that represent the oxidation potentials of DA and UA, respectively, with a separation of 260 mV. Amperometric measurements show that the response current of Au-DT/MOA linearly depends on DA in the range of 0.01–5 μM. The sensitivity of the Au-DT/MOA modified electrode is 20-fold that of the MOA-coated electrode. The proposed electrode has a low detection limit of 20 nM for DA at a signal to noise ratio of 3 and resistance to UA interference, showing no response current with UA addition and no obvious decrease in the sensitivity of DA detection in the presence of UA. Moreover, the performances of the developed electrode, including sensitivity, recovery, and reproducibility, are validated for detecting DA in non-diluted human urine, with satisfactory results.