Engineering Cobalt-Doped Nickel Oxide/Gadolinium-Doped Cerium Dioxide Heterojunction Nanofibers for Highly Selective and Sensitive Dopamine Detection.

Dopamine (DA) and serotonin (SN) are important catecholamine neurotransmitters in the central nervous system that play key roles in muscle stimulation and transmission of signals. DA release in the brain plays a key role in the regulations of pleasure and pain while SN helps to relay messages from one area of the brain to another. Abnormal DA levels are associated with serious diseases such as Schizophrenia and Parkinson’s. Imbalance in SN levels affects the muscles and cardiovascular system. Thus developing methods for detection of DA and SN in the presence of interfering species is an important area of research. Electrochemical methods for DA and SN detection have been developed since there is increasing demand for more reliable and rapid methods. Excess levels of interfering species such as ascorbic acid (AA) and uric acid (UA) co-exist in biological samples. These pose problems for DA and SN detection during electrochemical measurements since they all oxidize around the same potential region. Several types of electrode modifications have been reported for selective detection of DA and SN, but each one has its own advantages and limitations. The use of clay-composite modified electrodes have not been exploited. This work aims to employ clay composite modified glassy carbon electrodes for selective detection of DA and SN. The goal is to use clay composites to exclude AA and UA while enhancing DA and SN detection. Clay film serves as the polymeric membrane as clays are able to form membrane-like films. Clays are naturally occurring and much more stable than synthetic membranes. Clay film on an electrode surface provides important functions such as charge-exclusion and catalysis of electrochemical reactions. The clay composite was prepared by incorporating methylene blue and xanthate into clay interlayers by simply mixing them with clay suspension and sonicating. Several voltammetric experiments were undertaken to investigate the behavior of DA, SN, AA, and UA at the bare electrode (BE), clay modified electrode (CME), glycerol-clay modified electrode (GCME), glycerol-methylene blue-clay modified electrode (GMBCME), glycerol-xanthate-clay modified electrode (GXTCME), and glycerol-methylene blue-xanthate-clay modified electrode (GMBXTCME). Voltammetric techniques used were Cyclic Voltammetry (CV), Square-Wave Voltammetry (SWV), and Differential-Pulse Voltammetry (DPV). Experiments were performed at the physiological pH of 7.4. Glycerol was added to prevent cracks in films. At GCME, calibration curves by CV show linear range of 0.0010 – 0.25 and 0.0010 – 0.10 mM for DA and SN, respectively. The DA and SN oxidation peak potentials are around 0.26 and 0.27 V versus Ag/AgCl, respectively. For a mixture of DA and SN, the CV shows an oxidation peak around 0.43 V (due to SN) with a small hump around 0.28 V (due to DA). The hump is more pronounced at the GCME than at the BE, indicating catalytic effect by the clay on DA. For a mixture of DA, SN, AA, and UA, one broad oxidation peak is observed. Oxidation currents for both AA and UA at GCME are much lower than those at BE. This is evidenced by the fact that at pH of 7.4, AA and UA exist in their anionic form while DA and SN exist in the cationic form. Most clay layer surfaces are negatively charged so readily attract the cationic DA/SN into the interlayers and repel the anionic AA/UA. This enhances DA/SN detection while diminishing AA/UA detection. Only clay does not efficiently exclude AA/UA, hence the incorporation of methylene blue and xanthate. At GMBCME, both DA and SN exhibit oxidation potential at 0.20 V. However, a mixture of DA and SN exhibits peak potentials at 0.22 (DA) and 0.32 V (SN). Hence, the GMBCME film is able to separate and distinguish between the two peaks. It is also observed that both DA and SN peak potentials shift slightly negative compared to the BE. The DA peak currents increased at GMBCME compared to BE, while those of SN decreased. This confirms the catalytic effect of clay on DA stated above, but little or insignificant catalytic effect on SN. Again, GMBCME is unable to efficiently exclude AA and UA. With the addition of xanthate to form GMBXTCME, no oxidation peaks for AA and UA are seen. This is true for all three voltammetric techniques. This implies that the glycerol-methylene blue-xanthate-clay composite film efficiently discriminates against AA and UA detection. GMBXTCME film stability was also investigated and was observed that all old films exhibited great stability, reproducible results, and efficiently exclude both AA and UA. REFERENCES 1. T. Selvaraju, R. Ramaraj, J. Appl. Electrochem., 33, 759 (2003). 2. J.-M. Zen, P.-J. Chen, Anal. Chem., 69, 5087 (1997).

Effect of the carboxyl functional group at the edges of graphene on the signal sensitivity of dopamine detection

Clay Composite Modified Electrodes I: Voltammetric Method for Selective Analysis of Dopamine and Ascorbic Acid

Dopamine (DA) is a catecholamine neurotransmitter secreted by the human adrenal medulla and is related to many medical diseases. The rapid and sensitive detection of DA levels in physiological media is attracting attention. This paper has developed a fluorescence paper-based sensor using CdTe quantum dots (QDs)-rod nanozinc 5, 10, 15, 20-tetra (4-pyridyl)-21H-23H-porphine (nanoZnTPyP) for sensitive and visual detection of DA. After adding DA, the original quenching fluorescence of the CdTe QDs-rod nanoZnTPyP sensor was effectively restored. The detection mechanism may be that the oxidation of DA to the alkaline CdTe QDs-rod nanoZnTPyP solution produced DA-quinine, and the recovery of fluorescence was caused by the electronic effect of DA-quinine and rod-shaped nanoZnTPyP. The detection range is 0.5∼10 nmol/L, and the limit of detection (LOD) is 0.38 nmol/L (S/N = 3). The sensor system was used on paper device to detect significant changes in the fluorescent color of DA at different concentrations. In addition, this method has been successfully used for the determination of DA in human plasma. The sensor system is simple, easy to operate, and has high selectivity for possible DA interfering substances, which provided new ideas for detecting DA and Parkinson's disease, Alzheimer's disease, and other DA-related diseases.

Highly sensitive and selective electrochemical detection of dopamine based on CuCrO2-TiO2 composite decorated screen-printed modified electrode

Dopamine (DA) is a small biological molecule that causes a variety of diseases when its concentration is abnormal. Therefore, highly sensitive detection of DA is very important for the development of biomedicine and monitoring of human health. Herein, we prepared a carbon cloth (CC)/Ti3C2Tx/NiCoP composite as a highly sensitive electrochemical sensor for DA detection. Porous NiCoP was grown on the surface of CC and Ti3C2Tx by hydrothermal and phosphating treatments. The composite integrated the advantages of large specific surface area of zero-dimensional NiCoP quantum dots, rich electrochemical active sites of one-dimensional porous NiCoP nanowires, hydrophilicity of two-dimensional Ti3C2Tx nanosheets, and high conductivity of three-dimensional CC substrates. The sensor has high sensitivity (31.4101 μA μM–1 cm–2), wide detection range (0.17–784.55 μM), low detection limit (0.18 nM), elevated stability, and anti-interference ability. By analyzing the conductivity, hydrophilicity, and electrochemically active surface area of the CC/Ti3C2Tx/NiCoP composite, the reasons for its excellent performances are revealed for DA detection. At present, the research on NiCoP mainly focuses on hydrogen evolution, oxygen evolution, and supercapacitor. This research provides a regulatory strategy for the application of phosphide materials in sensors.

NO2-functionalized metal–organic framework incorporating bimetallic alloy nanoparticles as a sensor for efficient electrochemical detection of dopamine

Facile detection of dopamine (DA) in biological samples for diagnostics remains a challenge. This paper reported an effective fluorescent sensor based on adenosine capped CdSe/ZnS quantum dots (A-QDs) for highly sensitive detection of DA in human urine samples. In this assay, adenosine serves as a capping ligand or stabilizer for QDs to render high-quality QDs dispersed in water, and as a receptor for DA to attach DA onto the surface of A-QDs. DA molecules can bind to A-QDs via non-covalent bonding, leading to the fluorescence quenching of A-QDs due to electron transfer. The A-QDs based fluorescence probe showed a limit of detection (LOD) of ca. 29.3 nM for DA detection. This facile method exhibited high selectivity and anti-interference in the presence of amino acid, ascorbic acid (AA), uric acid (UA) and glucide with 100-fold higher concentration in PBS solution. Furthermore, it was also successfully used in the detection of DA in the human urine samples with quantitative recoveries (94.80-103.40%).

Electrochemical biosensors for dopamine

Interference of ascorbic and uric acids on dopamine behavior at graphene composite surface: An electrochemical, spectroscopic and theoretical approach

P.1.h.046 - A novel method to study behavioral strategy in probabilistic learning in group housed mice

Abnormal dopamine (DA) levels in the human body are associated with severe health conditions, making their accurate detection crucial for early diagnosis and monitoring. Therefore, the development of a highly sensitive electrochemical sensor for DA detection is of significant importance in physiological, biochemical, pharmaceutical, and medical applications. In this study, screen-printed electrodes (SPEs) were fabricated using MoS2-based conductive inks containing varying concentrations of silver nanoparticles (Ag NPs) to enhance electrocatalytic activity. The ink composition included ethyl cellulose and polyvinylpyrrolidone (PVP) as binders, providing structural integrity and adhesion, while terpineol was used as the solvent to achieve the desired viscosity for smooth and consistent printing. The printed electrodes underwent comprehensive electrochemical characterization to assess their performance, including stability, reproducibility, and sensitivity. Electrochemical analysis revealed that the SPCE/MoS2-Ag,4 electrode exhibited the best sensing characteristics due to the optimized interaction between MoS2 and Ag NPs, which facilitated improved electron transfer and enhanced detection capability. The electroanalytical performance of the sensors was assessed using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry. The SPCE/MoS2-Ag,4 sensor demonstrated a wide linear detection range from 0.01 to 0.08 mM and an exceptionally low limit of detection (LOD) of 0.016 μM for DA. Additionally, the sensor exhibited excellent reproducibility, high sensitivity, and strong selectivity, making it a promising candidate for reliable dopamine detection in biomedical and clinical applications.

Electrochemical detection of dopamine using a bare indium–tin oxide electrode and scan rate control

A facile photoelectrochemical sensing platform for highly sensitive detection of dopamine secreted from nerve cells based on polydopamine sensitized TiO2 as photoelectric material.

Resorcinol (Res) and Res-motif-containing molecules have been explored for the design and construction of fluorometric probes toward dopamine (DA) detection. However, the self-polymerization of DA under alkaline conditions competes with the probe-DA reaction, reducing the stability and sensitivity of detection. In this study, a target-triggered cascade reaction strategy has been explored for the development of DA detection probe based on the formation of borate ester intermediates. As a case study, 3-hydroxybenzeneboronic acid (HBBA) was exploited for stable and sensitive DA detection by inhibiting DA self-polymerization. The mechanism study disclosed that DA first reacts with HBBA and forms borate ester, which is then oxidized and hydroxylated to produce Res and DA, further forming fluorescent azamonardine compounds. Using HBBA as the probe, DA detection was achieved with a detection limit of 0.4 nM. In addition, the practical application of the HBBA probe was verified by accurate DA analysis in urine and cerebrospinal fluid samples.