Development and Application of Dopamine Biosensor Using Nano-gold Materials/Self-assembled Monolayers Modified Microelectrodes

• Main Authors: Tien-ChunTsai, 蔡田畯
• Other Authors: Jia-Jin Chen
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/34430045178253933904

博士 === 國立成功大學 === 生物醫學工程學系 === 100 === Parkinson’s disease (PD) resulted from a deficiency of dopaminergic neurons in the substantia nigra of midbrain is characterized by muscular rigidity, tremor, and gait problems. Electrochemical detections of in vivo dopamine (DA) can provide direct evidences for monitoring the DA depletion on animal model of PD but faces substantial amount of electroactive interferences in the brain, such as ascorbic acid (AA) and uric acid (UA). In this study, we proposed that utilization of nano-gold materials and self-assembled monolayer (SAM) to modify macroelectrodes and needle-type microelectrodes for improving sensitivity of DA recording as well as repelling AA and UA interferences. As regards Au-NP/SAM modified microelectrodes coupling with amperometric i–t measurements, in vitro tests have shown that the sensitivity of platinum microelectrode coated with Au-NP and 3-mercaptopropionic acid (MPA) was 2.7-fold that of conventional Nafion modification. Moreover, the DA sensing features of Au-NP/MPA modified microelectrodes including the fast response time (below 2 s), a low detection limit (7 nM), good reproducibility (± 2.4% relative standard deviation) as well as the resistances of AA interference and albumin adhesion were observed. In order to validate the feasibility of DA monitoring in rat’s brain, Au-NP/MPA modified microelectrodes have been successfully applied for the implantable detections in the striatum of anethetized rats with various parameters of deep brain electrical stimulations including different intensities, frequencies or inhibitor administration (e.g. nomifensine) of DA uptake. The determination of DA in urine samples is a promising technique for the non-invasive DA monitoring, but current electrochemical techniques face substantial interferences from UA due to similar electroactive characteristics. A combination of three-dimensional gold nanodendrite (Au-DT) and SAM onto the gold electrodes was proposed to improve sensitivity and specificity to DA and alleviate UA interference. With the optimum choice of ω-mercaptoalkane carboxylic acid chain length, the differential pulse voltammetry (DPV) of Au-DT deposited electrode coated with 8-mercaptooctanoic acid (MOA) showed two remarkable voltammetric peaks representing the oxidation potentials of DA and UA with a potential separation of 260 mV. Using amperometric measurement, the responsive current of Au-DT/MOA linearly depends on DA over the range of 0.01–5 μM with a correlation coefficient of 0.999 and more importantly the sensitivity is 20-fold of the MOA coated electrode. Other important features include a low detection limit of 0.02 μM for DA at a signal to noise ratio of 3 and resistance to UA interference, showing no responsive currents for UA additions and no obvious decrease on the sensitivity of DA detections in the presence of UA. Moreover, the performances of our designed electrode, such as a good sensibility, recovery and reproducibility, were successfully validated for detecting DA in non-diluted human urine with satisfactory results. The developed electrodes present more attractive features than conventional options for the urinary DA monitoring.