Detection Of Dopamine Research Articles

Simultaneous Dopamine and Serotonin Monitoring in Freely Moving Crayfish Using a Wireless Electrochemical Sensing System.

Dopamine (DA) and serotonin (5-HT) are neurotransmitters that regulate a wide range of physiological and behavioral processes. Monitoring of both neurotransmitters with real-time analysis offers important insight into the mechanisms that shape animal behavior. However, bioelectronic tools to simultaneously monitor DA and 5-HT interactive dynamics in freely moving animals are underdeveloped. This is mainly due to the limited sensor sensitivity with miniaturized electronics. Here, we present a semi-implantable electrochemical device achieved by integrating a multi-surface-modified carbon fiber microelectrode with a miniaturized potentiostat module to detect DA and 5-HT in vivo with high sensitivity and selectivity. Specifically, carbon fiber microelectrodes were modified through electrochemical treatment and surface coatings to improve sensitivity, selectivity, and antifouling properties. A customized, lightweight potentiostat module was developed for untethered electrochemical measurements. Integrated with the microelectrode, the microsystem is compact (2.8 × 2.3 × 2.1 cm) to minimize its impacts on animal behavior and achieved simultaneous detection of DA and 5-HT with sensitivities of 48.4 and 133.0 nA/μM, respectively, within submicromolar ranges. The system was attached to the crayfish dorsal carapace, allowing electrode implantation into the heart of a crayfish to monitor DA and 5-HT dynamics, followed by drug injections. The semi-implantable biosensor system displayed a significant increase in oxidation peak currents after DA and 5-HT injections. The device successfully demonstrated the application for in vivo simultaneous monitoring of DA and 5-HT in the hemolymph (i.e., blood) of freely behaving crayfish underwater, yielding a valuable experimental tool to expand our understanding of the comodulation of DA and 5-HT.

Morin‐enabled ratiometric dopamine detection by forming azamonardine product

AbstractThe important role to neuron communication and brain functions makes the selective and accurate detection of dopamine (DA, a typical neurotransmitter) significant. In this study, a morin‐based probe has been reported for the ratiometric DA detection. The mechanism study discloses that the inside resorcinol motif can specifically react with DA and form fluorescent azamonardine‐like product. In addition, the intrinsic emission from the internal chromophore endows ratiometric variation. With these features, selective DA sensing is realized using morin probe with a limit of detection of 2.2 nM (S/N = 3). Moreover, the practical application of the proposed method is further validated by the accurate DA determination in urine samples. This work demonstrates the possible exploration of novel small molecule‐based ratiometric‐sensing systems toward various analytes with the combination of proper reaction motif and chromophore. It is expected that the development of versatile probes for the ratiometric and accurate recognition of environmental and biological markers can refer such a design strategy.

Butea monosperma aided green synthesis of α-MoO3 nanoparticles: Biosensing and photocatalytic activity towards hazardous dyes and rangoli colorants

Increasing environmental pollutants and the need for efficient photocatalytic and biosensing materials have led to the development of novel green synthesis methods. In this study, MoO3 nanoparticles (NPs) were successfully synthesized by using green chemistry approach. In that respect, Butea monosperma leaf powder was used as a novel fuel. Structural parameters, optical properties, shape and morphology of MoO3 NPs are examined using XRD, FTIR, UV–Vis spectrophotometer, Photoluminescence (PL), SEM - EDAX and TEM analysis. The use of MoO3 NPs as a dusting agent in fingerprint applications results in improved fingerprint visibility, which is useful in forensic investigation. In this study, we modified the GCE electrode surface with MoO3 NPs to develop a highly sensitive dopamine (DA) sensor. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV) were used to investigate the electrochemical behaviour and electrocatalytic property of the MoO3 NPs. The synthesized NPs have excellent performance for detection of highly sensitive biologically active DA. The sensor exhibits a low detection limit of 0.45 μM. Additionally, it shows good stability, simplicity, and selectivity for the rapid detection of DA. MoO3 NPs shows good photocatalytic activity under UV light for the degradation of important textile industries dye such as methylene blue (MB) and harmful rangoli colors which are available in local shops of Tumkur, Karnataka. The photocatalyst exhibits a remarkable 97 % degradation efficiency for MB dye. Coumarin studies ensure the effective generation of OH radicals on the surface of the photocatalyst, leading to the degradation of organic dyes. Additionally, the MoO3 NPs reusability was examined, and even after four cycles, the level of photocatalytic activity did not drop much. Therefore, it is a potential photocatalyst for the processing of organic colours.

Optimized Fabrication of Carbon-Fiber Microbiosensors for Codetection of Glucose and Dopamine in Brain Tissue.

Dopamine (DA) signaling is critically important in striatal function, and this metabolically demanding process is fueled largely by glucose. However, DA and glucose are typically studied independently and, as such, the precise relationship between DA release and glucose availability remains unclear. Fast-scan cyclic voltammetry (FSCV) is commonly coupled with carbon-fiber microelectrodes to study DA transients. These microelectrodes can be modified with glucose oxidase (GOx) to generate microbiosensors capable of simultaneously quantifying real-time and physiologically relevant fluctuations of glucose, a nonelectrochemically active substrate, and DA, which is readily oxidized and reduced at the electrode surface. A chitosan hydrogel can be electrodeposited to entrap the oxidase enzyme on the sensor surface for stable, sensitive, and selective codetection of glucose and DA using FSCV. This strategy can also be used to entrap lactate oxidase on the carbon-fiber surface for codetection of lactate and DA. However, these custom probes are individually fabricated by hand, and performance is variable. This study characterizes the physical nature of the hydrogel and its effects on the acquired electrochemical data in the detection of glucose (2.6 mM) and DA (1 μM). The results demonstrate that the electrodeposition of the hydrogel membrane is improved using a linear potential sweep rather than a direct step to the target potential. Electrochemical impedance spectroscopy data relate information on the physical nature of the electrode/solution interface to the electrochemical performance of bare and enzyme-modified carbon-fiber microelectrodes. The electrodeposition waveform and scan rate were characterized for optimal membrane formation and performance. Finally, codetection of both DA/glucose and DA/lactate was demonstrated in intact rat striatum using probes fabricated according to the optimized protocol. Overall, this work improves the reliable fabrication of carbon-fiber microbiosensors for codetection of DA and important energetic substrates that are locally delivered to the recording site to meet metabolic demand.

Reliable ratiometric colorimetric monitoring of dopamine in practice based on the catalytic signal amplification of nano CeO2/CuO modified carboxylated chitosan

To reliably monitor dopamine (DA), a common neurotransmitter, a kind of nano CeO2/CuO modified carboxylated chitosan nanozyme (CeO2/CuO@CC) was constructed under microwave-assisted conditions. The proposed CeO2/CuO@CC exhibited superior synergistic- enhancement oxidase-like activity, with high specific surface area and superior stability. It could accelerate the oxidization of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) into blue oxTMB in the air. What’s more, the presence of trace DA could exclusively change the enzyme-like activity of CeO2/CuO@CC, accompanied with visual color changes from blue to colorless. Under the optimized conditions, there expressed double ratiometric linear relationships between lg(A652/A285)/lg(A370/A285) and cDA, with a large linear range between 6.0 × 10−9 and 1.0 × 10−5 M of DA. When applied for visual detection of DA in real samples, the detection limit was low to 2.0 × 10−9 M with RSD % less than 4.14 %. The mechanisms for enhanced oxidase-mimic activity of CeO2/CuO@CC and its selective detection of DA were proposed. This work will offer an insight to design efficient nanozyme for visual detection of bio-analytes in practice.

Graphene Nanocomposite Ink Coated Laser Transformed Flexible Electrodes for Selective Dopamine Detection and Immunosensing.

Novel and flexible disposable laser-induced graphene (LIG) sensors modified with graphene conductive inks have been developed for dopamine and interleukin-6 (IL-6) detection. The LIG sensors exhibit high reproducibility (relative standard deviation, RSD = 0.76%, N = 5) and stability (RSD = 4.39%, N = 15) after multiple bendings, making the sensors ideal for wearable and stretchable bioelectronics applications. We have developed electrode coatings based on graphene conductive inks, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (G-PEDOT:PSS) and polyaniline (G-PANI), for working electrode modification to improve the sensitivity and limit of detection (LOD). The selectivity of LIG sensors modified with the G-PANI ink is 41.47 times higher than that of the screen-printed electrode with the G-PANI ink modification. We have compared our fabricated bare laser-engraved Kapton sensor (LIG) with the LIG sensors modified with G-PEDOT (LIG/G-PEDOT) and G-PANI (LIG/G-PANI) conductive inks. We have further compared the performance of the fabricated electrodes with commercially available screen-printed electrodes (SPEs) and screen-printed electrodes modified with G-PEDOT:PSS (SPE/G-PEDOT:PSS) and G-PANI (SPE/G-PANI). SPE/G-PANI has a lower LOD of 0.632 μM compared to SPE/G-PEDOT:PSS (0.867 μM) and SPE/G-PANI (1.974 μM). The lowest LOD of the LIG/G-PANI sensor (0.4084 μM, S/N = 3) suggests that it can be a great alternative to measure dopamine levels in a physiological medium. Additionally, the LIG/G-PANI electrode has excellent LOD (2.6234 pg/mL) to detect IL-6. Also, the sensor is successfully able to detect ascorbic acid (AA), dopamine (DA), and uric acid (UA) in their ternary mixture. The differential pulse voltammetry (DPV) result shows peak potential separation of 229, 294, and 523 mV for AA-DA, DA-UA, and UA-AA, respectively.

The Simultaneous Detection of Dopamine and Uric Acid In Vivo Based on a 3D Reduced Graphene Oxide–MXene Composite Electrode

Dopamine (DA) and uric acid (UA) are essential for many physiological processes in the human body. Abnormal levels of DA and UA can lead to multiple diseases, such as Parkinson’s disease and gout. In this work, a three-dimensional reduced graphene oxide–MXene (3D rGO-Ti3C2) composite electrode was prepared using a simple one-step hydrothermal reduction process, which could separate the oxidation potentials of DA and UA, enabling the simultaneous detection of DA and UA. The 3D rGO-Ti3C2 electrode exhibited excellent electrocatalytic activity towards both DA and UA. In 0.01 M PBS solution, the linear range of DA was 0.5–500 µM with a sensitivity of 0.74 µA·µM−1·cm−2 and a detection limit of 0.056 µM (S/N = 3), while the linear range of UA was 0.5–60 µM and 80–450 µM, with sensitivity of 2.96 and 0.81 µA·µM−1·cm−2, respectively, and a detection limit of 0.086 µM (S/N = 3). In 10% fetal bovine serum (FBS) solution, the linear range of DA was 0.5–500 µM with a sensitivity of 0.41 µA·µM−1·cm−2 and a detection limit of 0.091 µM (S/N = 3). The linear range of UA was 2–500 µM with a sensitivity of 0.11 µA·µM−1·cm−2 and a detection limit of 0.6 µM (S/N = 3). The modified electrode exhibited advantages such as high sensitivity, a strong anti-interference capability, and good repeatability. Furthermore, the modified electrode was successfully used for DA measurement in vivo. This could present a simple reliable route for neurotransmitter detection in neuroscience.

In situ detection of dopamine in single living cells by molecularly imprinted polymer-functionalized nanoelectrodes

In situ detection of dopamine (DA) at single-cell level is critical for exploring neurotransmitter-related biological processes and diseases. However, the low content of DA and a variety of distractors with similar oxidation potentials as DA in cells brought great challenges. Here, a sensitive and specific electrochemical nanosensor was proposed for in situ detection of DA in single living cells based on nanodiamond (ND) and molecularly imprinted polymer (MIP)-functionalized carbon fiber nanoelectrode (ND/MIP/CFNE). Due to its excellent electrocatalytic property, ND was modified to the surface of CFNE based on amide bonding. Compared with bare CFNE, ND-modified CFNE can enhance oxidation currents of DA by about 4-fold, improving signal-to-noise ratio and detection sensitivity. MIP was further electropolymerized on the surface of nanoelectrodes to achieve specific capture and recognition of DA, which could avoid the interference of complex matrix and analogs in cells. Taking advantage of the precise positioning capability of a single-cell analyzer and micromanipulator, ND/MIP/CFNE could be precisely inserted into different locations of single cells and monitor oxidation signal of DA. The concentration of DA in the cytoplasm of single pheochromocytoma (PC12) cell was measured to be about 0.4 μM, providing a sensitive and powerful method for single-cell detection. Furthermore, the nanoelectrodes can monitor the fluctuation of intracellular DA under drug stimulation, providing new ideas and methods for new drug development and efficacy evaluation.

Silicene's intriguing nanozymatic activity: Improved colorimetric and electrochemically supported colorimetric biosensing

Silicene is a material that is largely studied via theoretical models. In the practical world, lengthy incubation times and poor sensitivity of colorimetric detection methods have limited their implementation. This paper transforms silicene's theoretical advantages into practical applications, presenting it as a tangible solution for significantly improving colorimetric biosensing. More specifically, this paper presents a pivotal breakthrough by not only documenting the remarkable nanozymatic activity of silicene in oxidizing 3,3′,5,5′-Tetramethylbenzidine (TMB) with hydrogen peroxide (H2O2), but also leveraging silicene’s inherent electronic properties to enhance the speed and precision of the peroxidase reaction, thereby improving its performance and advancing applicability. Two detection mechanisms were tested to observe the influence of silicene’s electronic scope; one in the absence and the other in the presence of an externally supplied electric potential. Both were successful in the detection of H2O2 and dopamine. The latter proved to be more favorable as it not only shortened the incubation time from 30 min to 1.5 min but also exhibited lower Limit of Detection (LOD) values. To demonstrate, for dopamine, in a concentration range of 0 – 10 μM, the LOD was 4.13 μM without the electric potential and 2.21 μM with the electric potential. Similarly, in a second concentration range, the LOD values were 37.81 μM and 34.94 μM, respectively. Kinetic profiles indicated the superior affinity silicene has for TMB and H2O2. A selectivity test also indicated that the method has excellent selectivity towards dopamine.

Interfacial galvanic replacement strategy for Pd-doped NiFe MOF nanosheets with highly efficient dopamine detection.

Aninterfacial galvanic replacement strategy to controllable synthesize palladium nanoparticles (Pd NPs)-modified NiFe MOF nanocomposite on nickel foam, which served as an efficient sensing platform for quantitative determination of dopamine (DA). Pd NPs grown in situ on the nanosheets of NiFe MOF via self-driven galvanic replacement reaction (GRR) and well uniform distribution was achieved. This method effectively reduced the aggregation of metallic nanoparticles and significantly promoted the electron transfer rate during the electrochemical process, leading to improved electrocatalytic activity for DA oxidation. Remarkably, the precisely constructed biosensor achieved a low detection limit (LOD) of 0.068µM and recovery of 94.1% (RSD 6.7%, N = 3) for simulated real sample detection and also exhibited superior selectivity and stability. The results confirmed that the as-fabricated Pd-NiFe/NF composite electrode could realize the quantitative determination of DA and showed promising prospects in real sample biosensing.

Biofouling and performance of boron-doped diamond electrodes for detection of dopamine and serotonin in neuron cultivation media

Boron doped diamond has been considered as a fouling-resistive electrode material for in vitro and in vivo detection of neurotransmitters. In this study, its performance in electrochemical detection of dopamine and serotonin in neuron cultivation media Neurobasal™ before and after cultivation of rat neurons was investigated. For differential pulse voltammetry the limits of detection in neat Neurobasal™ medium of 2 µM and 0.2 µM for dopamine and serotonin, respectively, were achieved on the polished surface, which is comparable with physiological values. On oxidized surface twofold higher values, but increased repeatabilities of the signals were obtained. However, in Neurobasal™ media with peptides-containing supplements necessary for cell cultivation, the voltammograms were notably worse shaped due to biofouling, especially in the medium isolated after neuron growth. In these complex media, the amperometric detection mode at +0.75 V (vs. Ag/AgCl) allowed to detect portion-wise additions of dopamine and serotonin (as low as 1–2 µM), mimicking neurotransmitter release from vesicles despite the lower sensitivity in comparison with neat NeurobasalTM. The results indicate substantial differences in detection on boron doped diamond electrode in the presence and absence of proteins, and the necessity of studies in real media for successful implementation to neuron-electrode interfaces.

Ultrasound assisted synthesis of CoFe-LDH for the simultaneous electrochemical detection of dopamine and acetaminophen

Herein, CoFe layered double hydroxide composites (CoFe-LDH) were synthesised by a simple ultrasound assisted synthesis method. It has been characterized by scanning electron microscopy (SEM), X-ray diffraction and X-ray photoelectron spectroscopy. CoFe-LDH modified glass carbon electrode was used as dual-function sensors for DA and AP detection. The sensor exhibits a wide detection linear range for DA and AP (2 μM-900 μM), low detection limits (DA: 0.08 μM; AP: 0.37 μM) (S/N = 3). The sensitivity of CoFe-LDH/GCE for DA and AP were 0.54 μA μM−1 cm−2 and 0.55 μA μM−1 cm−2. And it shows good reproducibility, selectivity, and stability. In addition, the sensor demonstrated good recovery rates for the detection of DA and AP in human serum samples.

Thiourea‐Modified Multiwalled Carbon Nanotubes as Electrochemical Biosensor for Ultra‐Precise Detection of Dopamine

Functionalized multi‐walled carbon nanotubes (MWCNTs) have enticed remarkable attention in the field of electrochemical sensing applications. Dopamine (DA) is a monoamine neurotransmitter released in the brain acting as a chemical messenger that communicates messages between nerve cells and the rest of the body. Therefore, there is a significant technological urge for the development of electrochemical sensors for DA in body fluids. In this context, nitrogen‐functionalized MWCNTs (TM‐CNT600) were fabricated by thermal annealing of carboxylic acid functionalized MWCNTs with thiourea at 600 oC under N2 atmosphere. The XPS spectrum reveals the presence of nitrogen‐containing functionalities in the as‐prepared TM‐CNT600. FTIR results show the presence of ‐OH, C‐N and C‐S functional groups. XPS further corroborates the FTIR results and quantifies the predominant functional groups in as‐prepared material. The material was investigated as a potential electrochemical sensor for the detection of dopamine (DA). In the case of TM‐CNT600/GCE, a linear relationship for DA concentration was observed in the range of 10.7 ‐ 24.2 μM with the limit of detection (LOD) of 1.42 μM using linear sweep voltammetry (LSV). These results highlight the potential of TM‐CNT600 modified GCE as an efficient sensor for the electrochemical detection of DA in body fluids.

A novel “off–on” ratiometric aptasensor based on dual-emissive persistent luminescent nanoparticles for the detection of dopamine

Dopamine, a neurotransmitter with multiple functions in the brain. The abnormal of dopamine levels are generally considered to be associated with various nervous system diseases. Herein, a novel ‘‘off–on” single-excited dual-emissive ratio luminescent aptasensor for highly sensitive and accurate monitoring of DA levels has been prepared via electrostatic interaction connecting persistent luminescent nanoparticles (PLNPs) ZnGaO:Sm and ZnGeO:Mn with different emission wavelengths. ZnGaO:Sm@Cy5.5-ZnGeO:Mn (ZGS@Cy5.5-ZGM), this ratiometric aptasensor exhibits two-emission peaks at 533 and 700 nm under a single-excitation wavelength of 254 nm. The afterglow luminescence of ZnGaO:Sm-apt@Cy5.5 at 700 nm is effective quenched by complementary chains of Cy5.5-modified DA aptamers with 710 nm specific absorption and only efficiently recovered by DA; meanwhile, the afterglow luminescence of ZnGeO:Mn as reference at 533 nm remains unchanged. The as-designed autofluorescence-free and exogenous-free interference ratiometric sensing system ZGS@Cy5.5-ZGM showed high selectivity for DA in complex biological samples. Under optimal detection conditions, the luminescence intensity ratio Δ(I700/I533) showed a good linear relationship with the concentration of DA in the range of 0.02–80 μM and the detection limit as low as 4 nM. The recoveries of DA in serum, urine and sweat were 97.4 % to 105.3 %, 96.4 % to103.4 %, and 95.1 % to 104.4 %, respectively. Current strategies based on PLNPs ratiometric sensors provide an effective method with high selectivity and accuracy for the detection of DA in clinical samples.

ZnO-CeO2 Hollow Nanospheres for Selective Determination of Dopamine and Uric Acid.

ZnO-CeO2 hollow nanospheres have been successfully synthesized via the hard templating method, in which CeO2 is used as the support skeleton to avoid ZnO agglomeration. The synthesized ZnO-CeO2 hollow nanospheres possess a large electrochemically active area and high electron transfer owing to the high specific surface area and synergistic effect of ZnO and CeO2. Due to the above advantages, the resulting ZnO-CeO2 hollow spheres display high sensitivities of 1122.86 μA mM-1 cm-2 and 908.53 μA mM-1 cm-2 under a neutral environment for the selective detection of dopamine and uric acid. The constructed electrochemical sensor shows excellent selectivity, stability and recovery for the selective analysis of dopamine and uric acid in actual samples. This study provides a valuable strategy for the synthesis of ZnO-CeO2 hollow nanospheres via the hard templating method as electrocatalysts for the selective detection of dopamine and uric acid.

Graphene derivative-based ink advances inkjet printing technology for fabrication of electrochemical sensors and biosensors

The field of biosensing would significantly benefit from a disruptive technology enabling flexible manufacturing of uniform electrodes. Inkjet printing holds promise for this, although realizing full electrode manufacturing with this technology remains challenging. We introduce a nitrogen-doped carboxylated graphene ink (NGA-ink) compatible with commercially available printing technologies. The water-based and additive-free NGA-ink was utilized to produce fully inkjet-printed electrodes (IPEs), which demonstrated successful electrochemical detection of the important neurotransmitter dopamine. The cost-effectiveness of NGA-ink combined with a total cost per electrode of $0.10 renders it a practical solution for customized electrode manufacturing. Furthermore, the high carboxyl group content of NGA-ink (13 wt%) presents opportunities for biomolecule immobilization, paving the way for the development of advanced state-of-the-art biosensors. This study highlights the potential of NGA inkjet-printed electrodes in revolutionizing sensor technology, offering an affordable, scalable alternative to conventional electrochemical systems.

A photoelectrochemical sensor based on In2O3/In2S3/ZnIn2S4 ternary Z-scheme heterojunction for ultrasensitive detection of dopamine in sweat.

A novel ternary heterojunction material In2O3/In2S3/ZnIn2S4 was synthesized, and a photoelectrochemical sensor was fabricated for the non-invasive test of dopamine (DA) in sweat. In2O3 multihollow microtubules were synthesized and then In2S3 was formed on their surface to construct a type-I heterojunction between In2S3 and In2O3. ZnIn2S4 was further introduced to form a Z-scheme heterojunction between In2S3/ZnIn2S4. Under photoexcitation, the photogenerated holes of In2O3 transferred to the valence band of In2S3, superimposed with the holes produced by In2S3, leads to a significantly higher photocatalytic oxidation capacity of In2O3/In2S3/ZnIn2S4 ternary composites than that of In2O3/In2S3. TheZ-scheme heterojunction accelerates the transfer of photogenerated electrons accumulated on the type-I heterojunction. In the presence of DA, itis rapidly oxidized into polydopamine (PDA) by In2O3/In2S3, and the benzoquinone groups of PDA compete for the photogenerated electrons to reduce the current in the external circuit, whereby DA determination is achieved. Owing to the combination of type-I and Z-scheme heterojunction, the sensor showed extremely high sensitivity, with a detection limit of 3.94 × 10-12 mol/L. It is one of the most sensitive methods for DA detection reported and has been applied to the determination of DA in human sweat.

Hydroxylase-like Biomimetic Nanozyme Synthesized via a Urea-Mediated MOF Pyrolytic Reconstruction Strategy for Non-"o-Phenol hydroxyl"-Dependent Dopamine Electrochemical Sensing.

Dopamine (DA), an essential neurotransmitter, is closely associated with various neurological disorders, whose real-time dynamic monitoring is significant for evaluating the physiological activities of neurons. Electrochemical sensing methods are commonly used to determine DA, but they mostly rely on the redox reaction of its o-phenolic hydroxyl group, which makes it difficult to distinguish it from substances with this group. Here, we design a biomimetic nanozyme inspired by the coordination structure of the copper-based active site of dopamine β-hydroxylase, which was successfully synthesized via a urea-mediated MOF pyrolysis reconstruction strategy. Experimental studies and theoretical calculations revealed that the nanozyme with Cu-N3 coordination could hydroxylate the carbon atom of the DA β-site at a suitable potential and that the active sites of this Cu-N3 structure have the lowest binding energy for the DA β-site. With this property, the new oxidation peak achieves the specific detection of DA rather than the traditional electrochemical signal of o-phenol hydroxyl redox, which would effectively differentiate it from neurotransmitters, such as norepinephrine and epinephrine. The sensor exhibited good monitoring capability in DA concentrations from 0.05 to 16.7 μM, and its limit of detection was 0.03 μM. Finally, the sensor enables the monitoring of DA released from living cells and can be used to quantitatively analyze the effect of polystyrene microplastics on the amount of DA released. The research provides a method for highly specific monitoring of DA and technical support for initial screening for neurocytotoxicity of pollutants.

Covalent organic frameworks surface-anchored with silver nanoparticles for colorimetric detection of dopamine based on its oxidase-mimicking activity

Sensitive detection of dopamine (DA) is essential for the diagnosis of nervous system diseases. Herein, a nanozyme-based colorimetric platform for DA determination was proposed. Using an imine-type covalent organic framework (COF-TD) as a host matrix, a nanozyme (AgNPs@COF-TD) was fabricated by anchoring silver nanoparticles (AgNPs) on the surface of COF-TD via in situ reduction of silver ions. Various characterization results confirmed the successful synthesis of flower-like AgNPs@COF-TD with surface-anchored AgNPs, which could expose more active sites. The as-prepared AgNPs@COF-TD exhibited satisfactory oxidase-mimicking activity with a low Km, which could catalyze the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxidized TMB (oxTMB) with significant absorbance at 657 nm. The introduction of DA not only reduced blue oxTMB to colorless TMB but also competed with TMB for the active sites of AgNPs@COF-TD, making a significant decrease in absorbance. Therefore, a label-free sensing strategy based on the oxidase-mimicking activity of AgNPs@COF-TD was successfully established for the colorimetric detection of DA, with a detection limit down to 0.2 μM. The practical applicability of this assay was further validated by analyzing DA-spiked human urine samples. This work provided a facile approach to prepare COF-based nanozymes, and demonstrated their great potential in colorimetric detection and bioanalysis.

Electrochemically selective detection of dopamine over serotonin by CuO/Cu2O bulk heterostructure electrode

Electrochemically selective detection of dopamine over serotonin by CuO/Cu2O bulk heterostructure electrode