Dopamine is a critical neurotransmitter and a clinically important biomarker in the human body. The abnormalities of dopamine levels can potentially lead to various neurological disorders like Parkinson’s and Alzheimer’s diseases.
Therefore, the rapid point-of-care recognition of dopamine levels would contribute to the advancement of nerve physiology and assist in diagnosis. Therefore, developing a single-use point-of-care dopamine sensor with excellent sensitivity and selectivity is of great interest.
The electrodes that use carbon-based nanomaterials have shown a great potential in various sensing devices. In that regard, graphene is a two-dimensional carbon material with unique properties: excellent conductivity, electrochemical activity, and a large surface area. Graphene is considered an excellent material platform for the development of electrochemical devices, including sensors, with a high-performance level. However, the scalable, low-cost production of graphene is a major issue that researchers of graphene would like to solve.
Laser scribed graphene (LSG) is a new member of the graphene family . Laser scribing provides a one-step route for graphene materials. In one approach, the LSG electrodes are generated by irradiation of a polyimide sheet with a universal CO2 laser. The resulting LSG was discovered to consist of few-layer graphene with excellent electrical and thermal conductivity and prominent electrochemical performance . The advantage of the LSG process is its cost efficiency compared with other graphene production methods, such as chemical vapor deposition (CVD), liquid phase exfoliation, and chemical reduction of graphene oxide.
In their recent report, Ph.D. candidate Guangyuan Xu, working in the laboratories of Prof. Jadranka Travas-Sejdic at the University of Auckland, New Zealand, developed a disposable dopamine-sensing device based on a modification of polyimide-LSG electrodes with a conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT). This work is the first to combine the unique electronic properties of LSG and PEDOT to make a superior sensing electrode for dopamine. The work has demonstrated that the active surface area of PEDOT-modified LSG electrodes is significantly larger compared to that of parent LSG electrodes, leading to better sensing. The PEDOT-modified LSG electrode measures the electrocatalytic activity towards the dopamine oxidation reaction. The PEDOT-modified LSG sensor also shows a significantly enhanced selectivity to dopamine sensing in the presence of common interference substances, in particular, ascorbic acid (AA) and uric acid (UA) (Figure 1).The electrochemical responses seen in Figure 1 show that the PEDOT-modified LSG electrode provides a significantly more sensitive response for the detection of dopanine. Guangyuan and his colleagues found an optimized 15 sec. of electrochemical deposition of PEDOT on the LSG electrodes gives a sensor with the highest sensitivity, where the DPV anodic peak current is a linear function of dopamine concentration, in the range from 1 to 150 µM, even in the presence of UA and AA interferences (Figure 2). The detection limit of the sensors for dopanine was evaluated to be 0.33 µΜ with a sensitivity of 0.22 ± 0.01 µA/µM, better than many other reported single-use sensors for dopamine. These findings are described in the article entitled, Sensitive, selective, disposable electrochemical dopamine sensor based on PEDOT-modified laser scribed graphene, recently published in the journal Biosensors and Bioelectronics. This work was conducted by Guangyuan Xu and Zahraa A. Jarjesa, supervised by Prof. Jadranka Travas-Sejdic, with further contributions from Valentin Desprez and Prof. Paul A. Kilmartin from the Polymer Electronics Research Centre at the University of Auckland.
Figures 1 and 2 are reused from Biosensors and Bioelectronics, Vol 107, Guangyuan Xu, Zahraa A. Jarjes, Valentin Desprez, Paul A. Kilmartin, Jadranka Travas-Sejdic., Sensitive, selective, disposable electrochemical dopamine sensor based on PEDOT-modified laser scribed graphene, Pages 184-191, Copyright (2018), with permission from Elsevier.
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