Patent Application
20230400430
This application claims the benefit of Korean Patent Application No. 10-2022-0072320, filed on Jun. 14, 2022, in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference for all purposes.
One or more example embodiments relate to an electrochemical sensor for simultaneous detection of dopamine and serotonin, a manufacturing method thereof, etc.
Since neurotransmitters not only maintain a nerve function, but also has an important effect on various nervous systems that interact between brain and nerves, dysregulation or imbalance of the neurotransmitters may cause several physiological and psychological diseases. Since dopamine (DA) and serotonin (5-hydroxytryptamine, 5-HT) among them are monoamine neurotransmitters widely distributed in the human body and brain, and play a role in regulating numerous behavioral and physiological functions, deficiency of these may cause mood-related disorders, depression, migraines, sexual disorders, Parkinson's disease, or the like. Therefore, monitoring of dopamine and serotonin is very important for the diagnosis of various diseases.
Nevertheless, most of the neural probes mainly used in the field of neuroscience or clinical are only focused on electrical nerve stimulation and neural signal recording, and there is a lack of tools for monitoring multiple neurotransmitters that are highly correlated with brain function regulation and brain disease causing.
Conventional methods for detecting neurotransmitters include high performance liquid chromatography (HPLC), liquid chromatography-electrospray tandem mass spectrometry (LC-ES tandem MS), surface enhanced Raman scattering spectroscopy (SERS), fluorescence, and the like. Although these methods are quite efficient, there are limitations in that detection time is long, a large amount of sample is required, sampling is complex, and expensive and bulky instruments are included. Therefore, it is essentially required to develop a miniaturized, high-sensitivity sensing electrode that can be utilized in monitoring of multiple neurotransmitters by being applied to a neural probe.
In order to overcome these limitations, an electrochemical detection method capable of simultaneous quantitative analysis with high sensitivity has been proposed. However, serotonin is difficult to distinguish from dopamine having a similar structure, and it is not easy to detect it since it is disturbed by interfering substances such as ascorbic acid (AA) and uric acid (UA). In addition, the detection of serotonin in physiological samples is negatively affected by electroactive metabolites so that there is a problem in that both selectivity and sensitivity are low.
Meanwhile, graphene oxide (GO) has attracted attention in various application fields since it can increase the sensitivity of the sensor as a catalyst support due to its high specific surface area and unique structure. GO has a unique ability to act as a versatile dispersant, has high biocompatibility, and has excellent electrocatalytic properties. However, the oxygen-functional groups in the GO sheet can be dispersed and readily soluble in water and other solvents so that there is a high possibility of causing instability in the analysis of real samples.
Accordingly, the present inventors obtained a reduced graphene oxide (rGO) through economical and environmentally friendly electrochemical reduction, and completed present disclosure by confirming that an electrochemical sensor containing the reduced graphene oxide (rGO), poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS), and Nafion is capable of simultaneously detecting dopamine and serotonin selectively and highly sensitively.
Example embodiments provide a working electrode containing a reduced graphene oxide (rGO), PEDOT:PSS, and Nafion.
Further, example embodiments provide an electrochemical sensor for simultaneous detection of dopamine and serotonin, including the working electrode, and a kit and a neural electrode system for simultaneous detection of dopamine and serotonin, including the same.
Further, example embodiments provide the working electrode, and a method for manufacturing an electrochemical sensor for simultaneous detection of dopamine and serotonin including the same.
Further, example embodiments provide a method for simultaneous detection of dopamine and serotonin using an electrochemical sensor for simultaneous detection of dopamine and serotonin including the working electrode.
However, the technical problems to be achieved by the present disclosure are not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.
According to an aspect, in order to solve the foregoing problems, there is provided an electrochemical sensor for simultaneous detection of dopamine and serotonin including a working electrode containing: a reduced graphene oxide (rGO); poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS); and Nafion.
As one example embodiment of the present disclosure, the reduced graphene oxide may be one in which a graphene oxide deposited on a gold (Au) thin film is electrochemically reduced by cyclic voltammetry (CV), and may be preferably one in which it is repeatedly reduced 3 to 6 times at a scan rate of 50 mV/s in the voltage range of −1.5 to 0 V.
As another example embodiment of the present disclosure, the reduced graphene oxide may be one which is reduced at pH 3 to 5, preferably at pH 4 at room temperature and atmospheric pressure. Specifically, since the sensor according to the present disclosure has the lowest interfacial impedance, the highest charge storage capacity and the highest Raman spectroscopy result's ID/IG ratio, of rGO at pH 4, it has the most excellent reduction rate.
As another example embodiment of the present disclosure, the sensor may further include: a counter electrode including a platinum (Pt) wire or a gold thin film; and a reference electrode including a silver/silver chloride (Ag/AgCl) or gold thin film.
As another example embodiment of the present disclosure, the sensor may be one capable of simultaneously detecting dopamine and serotonin selectively by lowering the signal of an interfering substance having a negative charge, and the interfering substance may be any one or more selected from the group consisting of ascorbic acid (AA), uric acid (UA), glucose, epinephrine (EP), norepinephrine (NE), and combinations thereof, but is not limited thereto.
According to another aspect, there is provided a kit for simultaneous detection of dopamine and serotonin including the electrochemical sensor for simultaneous detection of dopamine and serotonin.
According to another aspect, there is provided a neural electrode system for simultaneous detection of dopamine and serotonin including the electrochemical sensor for simultaneous detection of dopamine and serotonin.
As one example embodiment of the present disclosure, the sensor may include a working electrode containing: a reduced graphene oxide (rGO); poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS); and Nafion, a counter electrode, and a reference electrode.
As another example embodiment of the present disclosure, the system may be one in which pluralities of counter electrodes and reference electrodes paired with a plurality of working electrodes are disposed in proximity.
As another example embodiment of the present disclosure, the system may be one in which single counter electrode and reference electrode that share a plurality of working electrodes are disposed to be spaced apart from each other.
According to another aspect, there is provided a method for manufacturing an electrochemical sensor for simultaneous detection of dopamine and serotonin, the method comprising the steps of: (1) performing electrophoretic deposition of a graphene oxide (GO) on a gold (Au) thin film working electrode; (2) preparing a reduced graphene oxide (rGO) by electrochemically reducing the graphene oxide deposited on the gold thin film; (3) preparing PEDOT:PSS by electropolymerizing a mixed solution of EDOT and PPS on the prepared reduced graphene oxide; and (4) coating the prepared PEDOT:PSS with Nafion to prepare a working electrode.
As one example embodiment of the present disclosure, the step (1) may be to selectively deposit an electrode material on a gold thin film working electrode in a sensor composed of a working electrode, a counter electrode, and a reference electrode, and such a deposition method means that the electrode material can be evenly formed on the entire gold thin film having a desired current applied thereto.
As another example embodiment of the present disclosure, the step (1) may be to perform electrophoretic deposition of a graphene oxide dispersed in water at 1 μA for 1,000 to 1,500 seconds, preferably 1,200 seconds.
As another example embodiment of the present disclosure, the gold thin film of the step (1) may have a thin thickness of 50 to 150 nm, preferably 100 nm.
As another example embodiment of the present disclosure, the step (2) may be to perform electrochemical reduction after drying a gold thin film having the graphene oxide deposited thereon at room temperature, preferably to perform drying at room temperature for 5 hours.
As another example embodiment of the present disclosure, the step (2) may be to electrochemically reduce the graphene oxide-deposited gold thin film by cyclic voltammetry (CV), preferably to perform reduction 3 to 6 times at a scan rate of 50 mV/s in a voltage range of −1.5 to 0 V.
As another example embodiment of the present disclosure, the step (2) may be to reduce the graphene oxide-deposited gold thin film at room temperature and normal pressure at pH 3 to 5, preferably at pH 4.
As another example embodiment of the present disclosure, the step (3) may be to wash the prepared reduced graphene oxide in deionized water (DI water), dry it at room temperature, and then conduct electropolymerization.
As another example embodiment of the present disclosure, the mixed solution of EDOT and PPS in the step (3) may be one having a concentration ratio of EDOT:PPS of 1:10, preferably one in which 0.01 M of EDOT and 0.1 M of PPS are mixed.
As another example embodiment of the present disclosure, the step (3) may be to electropolymerize the mixed solution of EDOT and PPS at 16 μA for 200 to 400 seconds, preferably 300 seconds.
As another example embodiment of the present disclosure, the step (4) may be to perform coating by diluting Nafion and dropping a small amount of diluted Nafion, at this time, the concentration of Nafion may be preferably 0.5% by weight.
As another example embodiment of the present disclosure, the sensor may further include: a counter electrode including a platinum (Pt) wire; and a reference electrode including silver/silver chloride (Ag/AgCl).
According to another aspect, there is provided a method for simultaneous detection of dopamine and serotonin, the method comprising the steps of: (1) treating a biological sample isolated from an individual on an electrochemical sensor for simultaneous detection of dopamine and serotonin according to the present disclosure; and (2) performing differential pulse voltammetry (DPV) on the sample-treated sensor at pH 6 to 8.
As one example embodiment of the present disclosure, the step (2) may be performed to a pulse amplitude of 0.05 V, a pulse period of 0.2 seconds, a pulse width of 0.05 seconds, and a step potential of 0.004 V.
Additional aspects of example embodiments will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the disclosure.
According to example embodiments, the electrode (rGO/PEDOT:PSS/Nafion) containing: a reduced graphene oxide; PEDOT:PSS; and Nafion, and the electrochemical sensor including the same are an electrochemical-based neurotransmitter detection chip, which is simple to prepare, requires a small amount of sample, and enables response signal detection as fast as within 7 seconds.
According to example embodiments, an rGO/PEDOT:PSS/Nafion electrode and the electrochemical sensor including the same have a very low detection limit for dopamine and serotonin detection since they have high conductivity and catalytic activity based on a large surface area and an excellent electron-conducting support material by containing an rGO having excellent biocompatibility, PEDOT:PSS as a conductive polymer, and negatively charged Nafion.
According to example embodiments, the rGO/PEDOT:PSS/Nafion electrode and the electrochemical sensor including the same enable selective high-sensitivity detection by reducing the signal interference of ascorbic acid (AA), uric acid (UA), glucose, epinephrine (EP), and norepinephrine (NE) having structures similar to dopamine and serotonin.
According to example embodiments, the rGO/PEDOT:PSS/Nafion electrode and the electrochemical sensor including the same can deposit it stably to a uniform thickness since they selectively deposit a graphene oxide (GO) on a thin Au electrode under a low current without high potential application or prepared GO suspension's drop-coating. In addition, since the deposited GO is electrochemically reduced using a harmless buffer solution at room temperature without using a reducing agent such as hydrazine, hydroxylamine, or hydroquinone, production is easy, fast, economical, and environmentally friendly.
According to example embodiments, since the rGO/PEDOT:PSS/Nafion electrode and the electrochemical sensor including the same show high reproducibility and long-term stability even in the detection of dopamine and serotonin in real human serum, they are applied to an ultra-small neural probe and provide simultaneous monitoring of multiple neurotransmitters including dopamine and serotonin so that they can be used in the diagnosis fields of degenerative brain diseases including Parkinson's disease, and mental disease, or can be used in basic brain function research, biological research and drug treatment using changes in dopamine and serotonin concentrations, and biochip application fields.
According to example embodiments, the effects of the rGO/PEDOT:PSS/Nafion electrode and the electrochemical sensor including the same are not limited to those mentioned above, and other effects not mentioned will be able to be clearly understood to those skilled in the art from the description below.
These and/or other aspects, features, and advantages of the invention will become apparent and more readily appreciated from the following description of example embodiments, taken in conjunction with the accompanying drawings of which:
Since the electrochemical sensor including an rGO/PEDOT:PSS/Nafion electrode according to the present disclosure is manufactured by simply electropolymerizing PEDOT:PSS on a reduced graphene oxide (rGO) prepared at an optimal pH, and coating negatively charged Nafion thereon, it exhibits significantly improved catalytic properties and high conduction properties for the electroactivity of multiple neurotransmitters.
In order to confirm the dopamine and serotonin detection efficacy of the sensor, the present inventors carried out electrochemical characterization through electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV), and investigated the surface morphology, chemical state, and elemental composition of the electrode using a scanning electron microscope (SEM), Fourier-transform infrared (FT-IR) spectroscopy, Raman spectra, and high-resolution X-ray photoelectron spectroscopy (XPS).
As a result, it was confirmed that the electrochemical sensor including an rGO/PEDOT:PSS/Nafion electrode according to the present disclosure is capable of simultaneous high-sensitivity and selective detection of dopamine and serotonin by high affinity for cations.
Specifically, as a result of the electrochemical reaction, well-separated oxidation peaks were observed for mixtures containing various concentrations of dopamine and serotonin, and the dynamic sensing concentration ranges of dopamine and serotonin were shown to be 0.5 to 75 μM and 0.05 to 50 μM, respectively, and the detection limits were shown to be 0.5 and 0.05 μM, respectively. In the mixtures of dopamine and serotonin, the detection limits of dopamine and serotonin were 0.1 μM, and the sensitivities thereof were 99.3 and 86 μA/Mcm2, respectively. Moreover, the electrochemical sensor according to the present disclosure exhibited high selectivity, reproducibility, stability, and recovery rate in the human serum spike test.
Accordingly, the present disclosure provides an electrochemical sensor for simultaneous detection of dopamine and serotonin, including; a working electrode including a reduced graphene oxide (rGO), PEDOT:PSS, and Nafion; a counter electrode including a platinum (Pt) wire; and a reference electrode including silver/silver chloride (Ag/AgCl).
In the present disclosure, the “working electrode” refers to an electrode in which a reaction of interest occurs in an electrochemical experimental system, may also be referred to as a cathode or anode depending on whether the reaction occurring at the electrode is an oxidation reaction or a reduction reaction, and may be substituted for a “working electrode” and used. Non-limiting examples of the material of the working electrode may be metals such as copper, platinum, silver, gold, palladium, ruthenium, rhodium, and iridium, semiconductors such as carbon, GaAs, CdS, and In2O3, or materials with surface treatment for each material, but may be preferably a gold electrode. In the present disclosure, electrophoretic deposition of GO was simply performed on a gold (Au) thin film, reduction was performed in an optimal pH buffer medium to form an rGO, then electropolymerization was performed with EDOT:PSS to form PEDOT:PSS, and PEDOT:PSS was coated with Nafion to prepare a working electrode in which rGO/PEDOT:PSS/Nafion was patterned.
“PEDOT:PSS” refers to poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) known as a conductive polymer.
“Nafion” is a material having ion exchange properties, and is a kind of sulfonated tetrafluoroethylene based fluoropolymer-copolymer.
In the present disclosure, the “reference electrode” refers to an electrode that provides a reference potential, and for example, a potential difference, i.e., a voltage, may be established between the reference electrode and the working electrode.
In the present disclosure, the “counter electrode” refers to an electrode in an electrochemical circuit that acts as a current source or sink to complete the electrochemical circuit, and may be substituted for “a control electrode” and “a counter electrode” and used.
Further, the present disclosure provides a method for simultaneously detecting dopamine and serotonin from a biological sample isolated from an individual using the electrochemical sensor.
In the present disclosure, the “individual” is not limited as long as it is a mammal such as a livestock, a human, or the like, but may be preferably a human.
In the present disclosure, the “biological sample” is an analysis target for determining whether dopamine and/or serotonin is contained or not, or measuring the concentration, and may include all biological samples such as whole blood, blood cells, serum, plasma, bone marrow fluid, sweat, urine, tears, saliva, skin, mucosa, and the like, and may be preferably serum isolated from humans.
Further, the present disclosure provides an information providing method for diagnosing a brain-nervous system disease or a mental disease based on the concentrations of dopamine and serotonin measured using the electrochemical sensor.
In the present disclosure, the “brain-nervous system disease” may be Parkinson's disease, Alzheimer's disease, Huntington's disease, amyotrophic lateral sclerosis, Creutzfeldt-Jakob disease, Pick disease, stroke, multiple system atrophy, dementia due to head trauma, vascular disease dementia, frontotemporal dementia (FTD), Corticobasal degeneration (CBD), Progressive supranuclear palsy (PSP), Lewy body dementia, tangle-predominant senile dementia, Argyrophilic grain disease, FTDP-17, Lytico-Bodig disease, learning disability, mild cognitive impairment, agnosia, forgetfulness, aphasia, apraxia, delirium, multiple sclerosis, brain cancer, traumatic brain injury (TBI), thrombosis, em-bolism, transient ischemic attack, lacune, cerebral apoplexy, cerebral infarction, cerebral circulatory metabolic disorder, brain function coma, or the like, but is not limited thereto.
In the present disclosure, the “mental disease” may be depression, lethargy, hyperactivity, attention deficit, autism, post-traumatic stress disorder (PTSD), anxiety disorder, sleep disorder, panic disorder, intellectual disability, memory loss, drug addiction, schizophrenia, obsessive compulsive disorder, megalomaniac, personality disorder, alcoholism, bipolar disorder, or the like, and may include physical symptoms resulting therefrom, for example, fatigue, indigestion, difficulty breathing, and the like, but is not limited thereto.
The terms used in the embodiments are used for the purpose of description only, and should not be construed as an intention to limit the present disclosure. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present specification, it should be understood that a term such as “comprise”, “have”, or the like is intended to designate that a feature, a number, a step, an operation, a component, a part, or a combination thereof described in the specification exists, but it does not preclude the possibility of existence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.
Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as those commonly understood by one of ordinary skill in the art to which the embodiments belong. Terms such as those defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application.
The present disclosure can apply various transformations and can have various embodiments. Hereinafter, specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present disclosure to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and technical scope of the present disclosure. In describing the present disclosure, if it is determined that a detailed description of a related known technology may obscure the gist of the present disclosure, the detailed description thereof will be omitted.
To fabricate the flexible sensor configuration, polyimide (PI, VTEC 1388) was obtained from Richard Blaine International, Inc., Philadelphia, PA, USA. DNR-L300-30 was obtained from Dongjin, Seoul, Korea. AZ 9260 was obtained from AZ Electronic Materials, NJ, USA. Phosphate buffer saline (0.1 M PBS, pH 7.4) was obtained from Duksan General Science in Korea.
For the electrochemical reduction, the phosphate buffer solution containing K2HPO4 and KH2PO4 was adjusted to the preferred pH. Dopamine (DA), serotonin (5-HT), ascorbic acid (AA), uric acid (UA), glucose, epinephrine (EP), and norepinephrine (NE) were purchased from Sigma-Aldrich for electrochemical analysis. Commercially-sterilized and filtered human serum (derived from human male AB plasma, USA origin, code H4522) was obtained from Sigma-Aldrich for spike testing.
As shown in
The electrochemical performance of the sensor according to one embodiment of the present disclosure was evaluated at room temperature by Autolab (PGSTAT 302N, NOVA software, Ecochemie, Utrecht, The Netherlands). Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) were performed using an Au reference electrode, an Au counter electrode, an Au (diameter of 2.4 mm) working electrode, and prepared GO-based working electrodes (GO, rGO, rGO/PEDOT:PSS, and rGO/PEDOT:PSS/Nafion).
CV with a potential limit of −0.2 to 0.8 V was performed at a scan rate of 100 mV/s, and the frequency range of EIS was 1 to 105 Hz. The parameters of the DPV measurement were set as follows: a scan rate of 25 mV/s, a pulse width of 0.06 seconds, and an amplitude of 30 mV. To avoid spontaneous oxidation of dopamine and serotonin, fresh solutions were prepared daily and stored in a dark room at 4° C. All experiments were performed at ambient temperature. The selectivity of the rGO/PEDOT:PSS/Nafion electrode was investigated via the DPV oxidation current response to serotonin (1 μM). At this time, ascorbic acid (AA, 1,000 μM), uric acid (UA, 50 μM), glucose (100 μM), epinephrine (EP, 10 μM), and norepinephrine (NE, 10 μM) was tested in a 0.1 M PBS (pH 7.4). The reproducibility of rGO/PEDOT:PSS/Nafion was investigated through six electrodes and serotonin oxidation peak current. At this time, in order to evaluate the reproducibility and selectivity of serotonin detection in the 0.1 M PBS (pH 7.4), DPV was calculated with 1 μM of serotonin (n=3).
The surface morphology and elemental analysis of the electrodes were evaluated with a scanning electron microscope (SEM, Regulus 8230). Fourier transform infrared (FT-IR) spectra were captured using a Thermo Nicolet iS10 spectrometer and pelleted in KBr for FT-IR analysis. Raman spectra were recorded using a Renishaw Raman microscope with a neodymium-doped yttrium aluminum garnet laser containing a photon beam of a wavelength of 532 nm. X-ray photoelectron spectroscopy (XPS, Ulvac, Japan) was irradiated with a monochromatic AI Kα, X-ray source. XPS distribution analysis (XPS depth profiling) was performed in order to obtain the approximate thickness of the layer. A high-energy Ar+ ion beam having an acceleration voltage of 2 kV was used to sputter samples layer by layer on the top surface within an area of 1×1 mm2. After each successive sputter cycle, Au4f, C1s, F1s, O1s and S2p peak areas were registered and analyzed.
For practical validation of the sensor including the rGO/PEDOT:PSS/Nafion electrode for simultaneous detection of dopamine and serotonin, all serum samples were prepared without further processing or dilution. Various concentrations of dopamine and serotonin were tested in spiked serum samples. For quantitative analysis, the DPV current response of the sensor including the rGO/PEDOT:PSS/Nafion electrode was checked and compared with standard serotonin solution and serotonin spike serum through DPV. Current responses measured from spiked serum samples and standard solution that have various dopamine and serotonin concentrations were calculated and compared using recovery rate (% recovery rate=Ci/Co/Cx). At this time, Ci and Co are the serotonin concentrations experimentally obtained in the spike and blank serum samples, respectively, and Cx is the concentration of serotonin actually spiked in the serum samples.
Although GO can be electrochemically reduced in a wide pH range of 1.5 to 12.5, optimal pH conditions for the medium are essential to ensure that the rGO surface has excellent electrocatalytic properties. Reduced GO films were prepared through cyclic voltammetry for a potential range of −1.5 to 0 V in buffer solutions of various pH conditions.
As a result of Raman spectroscopy measurement for quantitative analysis of rGO in
Chemical transformation was confirmed by irradiating the fabricated GO, rGO, rGO/PEDOT:PSS, and rGO/PEDOT:PSS/Nafion electrodes with FT-IR.
To investigate the presence of different material layers in the rGO/PEDOT:PSS/Nafion electrode, XPS distribution analysis was performed for Au4f, C1s, F1s, O1s and S2p level regions.
To investigate the electrochemical performance of the fabricated working electrode, interfacial impedances and cyclic voltammetry of Au, GO, rGO, rGO/PEDOT:PSS, and rGO/PEDOT:PSS/Nafion electrodes were measured in a 0.1 M PBS solution (pH 7.4), and the results are shown in
PEDOT:PSS exhibited an extended current response indicating an increased number of electrochemically active sites. In the measured CV curves, the CSC values implying the accumulated charges gradually expanded in the order of Au<GO<rGO<rGO/PEDOT:PSS<rGO/PEDOT:PSS/Nafion, and exhibited values of 0.15, 1.14, 13.3, 22.6, and 15.6 mC/cm2, respectively. The rGO/PEDOT:PSS electrode was strengthened to have higher capacitance values after electrochemical reduction and deposition.
As shown in
The effects of the scan rates evaluated using the CV curves were shown in
The effect of pH on the oxidation of serotonin in a sensor including the rGO/PEDOT:PSS/Nafion electrode was investigated with DPV in the pH range of 5 to 9.
As shown in
To confirm the selective detection of dopamine and serotonin, the concentration of one species was fixed and the concentration of the other species was changed. Simultaneous detection of two analytes was performed by simultaneously changing the concentration of one species in the prepared mixture. As shown in
Compared with previous studies, the sensor according to the present disclosure exhibited excellent distinctiveness in the simultaneous response to dopamine and serotonin. The improved performance of the present disclosure may be due to the high catalytically active site of rGO/PEDOT:PSS/Nafion based on the surface, large surface area, and excellent electron-conducting support material of negatively charged Nafion.
The presence of interference is an important parameter determining the selectivity of the rGO/PEDOT:PSS/Nafion electrode for serotonin detection. The coexistence of serotonin and other interfering species may induce mixed response currents due to their close oxidation potential.
Therefore, the selectivities of the sensor including the rGO/PEDOT:PSS/Nafion electrode were investigated with DPV oxidation current responses of serotonin (1 μM).
According to Table 1, the peak oxidation currents of serotonin were maintained at 65 μA, and it was found that even if interfering substances with higher concentrations were present, the responses of serotonin DPV were not significantly interfered. Particularly, the oxidation potential of serotonin at 1,000 μM of ascorbic acid did not shift at 0.25 V due to repulsion from the negatively charged Nafion surface. Based on the above results, it was confirmed that the sensor including the rGO/PEDOT:PSS/Nafion electrode according to the present disclosure has higher anti-interference abilities for ascorbic acid, uric acid, glucose, epinephrine, and norepinephrine in the detection of serotonin. This means the excellent selectivity of the present disclosure for serotonin.
As shown in
In order to demonstrate that the sensor including the rGO/PEDOT:PSS/Nafion electrode according to the present disclosure can be used for clinical detection, a sensor including the rGO/PEDOT:PSS/Nafion electrode was tested, and spiked real serum samples were used to compare recovery rates.
The recovery rates were 93.3% to 101.8% (RSD, n=3) based on the detection of serotonin in human serum (Table 2), and the sensor including the rGO/PEDOT:PSS/Nafion electrode effectively detected serotonin from human serum samples.
Interestingly, the above results showed excellent recovery rates for 0.05 to 5 μM, indicating that the sensor according to the present disclosure can efficiently detect even low levels of serotonin in human serum, and reproducibility and feasibility are also very high. In addition, in order to investigate the detection of serotonin by the sensor including the rGO/PEDOT:PSS/Nafion electrode in the presence of dopamine, dopamine and serotonin (0.1 to 5 μM) were added to serum samples (Table 3).
The recovery rates of dopamine and serotonin were 89.4 to 93.3% and 89.1 to 96.1%, respectively, and the relative standard deviations (RSD) of three replicates were less than 5%. Therefore, the sensor including the rGO/PEDOT:PSS/Nafion electrode showed an excellent recovery range in undiluted serum samples, and this suggests that the present disclosure is suitable for detection of dopamine and serotonin in actual sample analysis.
Although Examples have been described with reference to the limited drawings as described above, those skilled in the art may apply various technical modifications and variations based on the above description. For example, although the described techniques are performed in an order different from the described method, and/or the constituent elements such as the described system, structure, apparatus, circuit, etc. are coupled or combined in a form different from the described method, or replaced or substituted by other constituent elements or equivalents, appropriate results may be accomplished.
Therefore, other embodiments, other Examples, and equivalents to the patent claim scope also belong to the scope of the claims to be described later.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2022-0072320 | Jun 2022 | KR | national |
