Electrochemical detection of dopamine with poly-glutamic acid patterned carbon nanotube electrodes

We selectively detected dopamine using poly-glutamic acid patterned single-walled carbon nanotube (PGA-SWCNT) films. Glutamic acid was electropolymerized on the surfaces of SWCNT films by repeated potential scanning, and the resulting sensor electrodes were used to detect dopamine in the presence of ascorbic acid and uric acid. Field emission scanning electron microscopy images characterizing SWCNT and PGA-SWCNT film electrodes showed a uniform carbon nanotube layer with homogeneous island clusters of PGA on the SWCNT film electrode. Cyclic voltammetry studies indicated that dopamine underwent two-electron, two-proton electrochemical oxidation at the PGA-SWCNT film that pH dependent. Different pulse voltammetry for dopamine oxidation at the PGA-SWCNT film electrode yielded a well-defined oxidation peak at 0.140V(vs. a saturated calomel electrode) in 0.1 M PBS buffer (pH 7.2). Dopamine detection was linear in the range of 3.3 to 26.6 μM(R²=0.994) and the limit of detection was estimated to be 0.38 μM. The proposed sensor is stable and reproducible with relative standard deviations of 2.58% and 0.98-3. 45%, respectively. The PGA-SWCNT film electrode also exhibited high selectivity for dopamine in the presence of interfering ascorbic acid and uric acid.