Electrochemical Detection of Dopamine at Fe3O4/SPEEK Modified Electrode

Reported here is the design of an electrochemical sensor for dopamine (DA) based on a screen print carbon electrode modified with a sulphonated polyether ether ketone-iron (III) oxide composite (SPCE-Fe₃O₄/SPEEK). L. serica leaf extract was used in the synthesis of iron (III) oxide nanoparticles (Fe₃O₄NPs). Successful synthesis of Fe₃O₄NP was confirmed through characterization using Fourier transform infrared (FTIR), ultraviolet–visible light (UV–VIS), X-ray diffractometer (XRD), and scanning electron microscopy (SEM). Cyclic voltammetry (CV) was used to investigate the electrochemical behaviour of Fe₃O₄/SPEEK in 0.1 M of phosphate buffer solution (PBS) containing 5 mM of potassium ferricyanide (III) solution (K₃[Fe(CN)₆]). An increase in peak current was observed at the nanocomposite modified electrode SPCE-Fe₃O₄/SPEEK) but not SPCE and SPCE-Fe₃O₄, which could be ascribed to the presence of SPEEK. CV and square wave voltammetry (SWV) were employed in the electroxidation of dopamine (0.1 mM DA). The detection limit (LoD) of 7.1 μM and 0.005 μA/μM sensitivity was obtained for DA at the SPCE-Fe₃O₄/SPEEK electrode with concentrations ranging from 5–50 μM. LOD competes well with other electrodes reported in the literature. The developed sensor demonstrated good practical applicability for DA in a DA injection with good resultant recovery percentages and RSDs values.

Smartphone-Based Electrochemical Potentiostat Detection System Using PEDOT: PSS/Chitosan/Graphene Modified Screen-Printed Electrodes for Dopamine Detection

In this work, a smartphone-based electrochemical detection system was designed and developed for rapid and real-time detection of dopamine (DA). The system included a screen-printed electrode (SPE) used as a sensor, a hand-held electrochemical potentiostat and a smart phone with a specially designed app. During the detection period, the SPEs modified with poly(3,4-ethylenedioxythiophene) (PEDOT), chitosan (CS) and graphene (G) were used to convert and amplify the electrochemical reaction signals. The electrochemical potentiostat was used to generate excitation electrical signals and collect the electrical signals converted from the sensor. The smartphone—connected to the detector via Bluetooth-was used to control the detector for tests, further process the uploaded data, and plot graphs in real time. Experimental results showed that the self-designed sensing system could be employed for highly selective detection of DA in the presence of interfering substances such as ascorbic acid (AA) and uric acid (UA). CV was carried out to characterize the electrochemical properties of the modified SPEs and the electrochemical behaviors of DA on the modified SPEs. Finally, according to the analysis of DPV responses of DA, the system could detect DA with a detection sensitivity of 0.52 ± 0.01 μA/μM and a limit of detection of 0.29 μM in the linear range of DA concentrations from 0.05 to 70 μM.

Recent Advances in Electrochemical and Optical Sensing of Dopamine

Nowadays, several neurological disorders and neurocrine tumours are associated with dopamine (DA) concentrations in various biological fluids. Highly accurate and ultrasensitive detection of DA levels in different biological samples in real-time can change and improve the quality of a patient's life in addition to reducing the treatment cost. Therefore, the design and development of diagnostic tool for in vivo and in vitro monitoring of DA is of considerable clinical and pharmacological importance. In recent decades, a large number of techniques have been established for DA detection, including chromatography coupled to mass spectrometry, spectroscopic approaches, and electrochemical (EC) methods. These methods are effective, but most of them still have some drawbacks such as consuming time, effort, and money. Added to that, sometimes they need complex procedures to obtain good sensitivity and suffer from low selectivity due to interference from other biological species such as uric acid (UA) and ascorbic acid (AA). Advanced materials can offer remarkable opportunities to overcome drawbacks in conventional DA sensors. This review aims to explain challenges related to DA detection using different techniques, and to summarize and highlight recent advancements in materials used and approaches applied for several sensor surface modification for the monitoring of DA. Also, it focuses on the analytical features of the EC and optical-based sensing techniques available.

SnO2 nanoparticle-coated ZnO nanotube arrays for high-performance electrochemical sensors

Novel 1D nanostructures offer new opportunities for improving the performance of electrochemical sensors. In this study, highly ordered 1D nanostructure array electrodes composed of SnO2 nanoparticle-coated ZnO (SnO2 @ZnO) nanotubes are designed and fabricated. The composite nanotube array architecture not only endows the electrochemical electrodes with large surface areas, but also allows electrons to be quickly transferred along the nanotubes. Modifying the SnO2 @ZnO nanotube arrays with negatively charged polymer film and employing them as a working electrode, sensitive and selective electrochemical detection of an important neurotransmitter, i.e., dopamine, is realized via the cycle voltammetry (CV) and differential pulse voltammetry (DPV) techniques. Interference from ascorbic acid can be successfully eliminated. The oxidative peak currents recorded from CV linearly depend on the dopamine concentrations from 0.1 to 100 μM with a sensitivity of 2.16 × 10(-7) A μM(-1) cm(-2) and detection limit of 45.2 nM. Using the DPV technique, an improved sensitivity and detection limit of 1.94 × 10(-6) A μM(-1) cm(-2) and 17.7 nM are respectively achieved. Moreover, the SnO2 @ZnO nanotube array electrodes can be reused through simple ultrasonical cleaning and no obvious deterioration is observed in the performance.