Overoxidized polyimidazole/graphene oxide copolymer modified electrode for the simultaneous determination of ascorbic acid, dopamine, uric acid, guanine and adenine

Accurate, affordable, and easy electrochemical detection of ascorbic acid in fresh fruit juices and pharmaceutical samples using an electroactive gelatin sulfonamide

In this study, we demonstrated how to design and construct a highly specific and sensitive sensor capable of rapidly and accurately detecting ascorbic acid (AA). A sulfonamide derivative (S) acting as a novel monomer was synthesized through an aldol condensation reaction. Subsequently, a free radical-mediated grafting polymerization approach was used to create a new generation of gelatin (Gel) grafted with poly sulfonamide derivative (Gel-g-PS). The graft percentage (GP%) was 60 ± 0.5% with a conversion rate of 98.3%. Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) were utilized to confirm the formation of Gel-g-PS. The developed gelatin sulfonamide modified screen printed electrode (Gel-g-PS/SPE) was employed for the determination of ascorbic acid (AA) in fruit juices and pharmaceutical samples. Gel-g-PS/SPE showed excellent electrochemical catalytic activities toward AA oxidation compared to bare (unmodified) SPE. Ascorbic acid displayed a sensitive oxidation peak at 0.35 V using the differential pulse voltammetry technique. Under optimized experimental conditions, the two linear ranges for AA detection were obtained to be from 0.2-5 ppb and 20-600 ppb, with a limit of detection (LoD) of 0.03 ppb and a limit of quantification (LoQ) of 0.11 ppb. The proposed Gel-g-PS modified SPE surface demonstrated good selectivity, stability, reproducibility, and repeatability as well as a good recovery rate in fresh fruit juices and pharmaceutical samples.

A flexible electrochemical sensor based on Fe-doped polydopamine derived carbon for simultaneous detection of dopamine and uric acid

A free-standing electrode based on carbon cloth-supported Fe-doped polydopamine-derived carbon (Fe/PDA-C/CC) was developed for the simultaneous detection of dopamine (DA) and uric acid (UA). First, dopamine was self-polymerized on the surface of the carbon cloth to obtain polydopamine coatings. Subsequently, Fe3+ was introduced through the formation of a coordinate bond with the hydroxyl functional group in the polydopamine layer. After calcination, a flexible and free-standing electrode was obtained. The sensing performance and mechanism of the Fe/PDA-C/CC sensor was investigated and is discussed in detail herein. Experimental results demonstrated that Fe/PDA-C/CC could simultaneously detect DA and UA with a wide detection range of 0.5-300 μM and 0.5-400 μM with low detection limits of 0.041 μM and 0.012 μM, respectively. Meanwhile, Fe/PDA-C/CC possessed excellent anti-interference performance, repeatability, stability, and accuracy in real samples. Overall, this study provides a facile and effective approach for simultaneous detection of UA and DA.

Electrochemical and quantum chemical approaches to the study of dopamine sensing using bentonite and l-cysteine modified carbon paste electrode

This work presents a significant investigation involving both electrochemical experiment and quantum chemical simulation approaches. The objective was to characterize the electrochemical detection of dopamine (DA). The detection was carried out using a modified carbon paste electrode (CPE) incorporating bentonite (Bent) and l-cysteine (CySH) (named as CySH/Bent/CPE). To understand and explain the oxidation mechanism of DA on the CySH/Bent modified electrode surface, the coupling of the two approaches were exploited. The CySH/Bent/CPE showed excellent electroactivity toward DA such as good sensibility, selectivity, stability, and regenerative ability. The developed sensor shows a dynamic linear range from 0.8 to 80 μM with a limit of detection and quantification of 0.5 μM and 1.5 μM, respectively. During the quantitative analysis of DA in presence of ascorbic acid (AA) and uric acid (UA) the electrochemical oxidation signals of AA, DA, and UA distinctly appear as three separate peaks. The potential differences between the peaks are 190 mv, 150 mv, and 340 mV for the AA-DA, DA-UA, and AA-UA oxidation pairs, respectively. These observations stem from square wave voltammetry (SWV) studies, along with the corresponding redox peak potential separations. The developed sensor is simple and accurate to monitor DA in human serum samples. On the other hand, CySH acts as an electrocatalyst on the CySH/Bent/CPE surface by increasing its active electron transfer sites, as suggested by the quantum chemical modeling with analytical results of Fukui. Furthermore, the voltammetric results obtained agree well with the theoretical calculations.

Electrochemistry detection of estrogenic effect: Regulation of de novo purine synthesis and catabolism by gibberellin and fulvestrant

The estrogenic effect of plant growth regulators has been received little attention, which leads to the lack of relevant toxicity data. In this study, the estrogenic effect induced by gibberellin with ERα-dependent manner was found by E-screen and western blot methods, and the electrochemical signals of MCF-7 cells regulated by gibberellin and fulvestrant were investigated. The results showed that the electrochemical signals of MCF-7 cells were increased by gibberellin, while reduced by fulvestrant significantly, and displayed an extremely sensitive response to the effects of estrogenic effect induced by ERα agonist and antagonist. Western blot results showed that the expressions of phosphoribosyl pyrophosphate amidotransferase and hypoxanthine nucleotide dehydrogenase in de novo purine synthesis and adenine deaminase in catabolism were more effective regulated by gibberellin and fulvestrant, resulting in significant changes of the levels of guanine, hypoxanthine and xanthine in cells, and then electrochemical signals. The results provide a theoretical basis for the establishment of new electrochemical detection method of the estrogenic effect of plant regulators.

A voltammetric sensor based on a reduced graphene oxide/β-cyclodextrin/silver nanoparticle/polyoxometalate nanocomposite for detecting uric acid and tyrosine

In the present work, an electrochemical sensor based on reduced graphene oxide/β-cyclodextrin/silver nanoparticle/polyoxometalate (RGO-CD-AgNP-POM) was developed for the simultaneous detection of uric acid (UA) and L-tyrosine (L-Tyr). First, an RGO-CD-AgNP-POM nanocomposite was synthesized via a simple photoreduction method and characterized by transmission electron microscopy (TEM), energy dispersive X-ray imaging (EDS), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA). As an electrode material, RGO-CD-AgNP-POM showed wide linear ranges (0.5-500 μM for UA, and 1-400 μM for L-Tyr) and relatively low detection limits (0.11 μM for UA, and 0.23 μM for L-Tyr). In addition, the combination of supramolecular recognition from CD and excellent electrochemical performances from RGO, AgNPs and POM was expected to enhance the sensing performances toward UA and L-Tyr in real samples with favorable recovery ranges (99%-104%). This nanocomposite provides a new platform for developing the family of electrode materials.

Functionalization of Graphene Derivatives with Conducting Polymers and Their Applications in Uric Acid Detection

In this article, we review recent progress concerning the development of sensorial platforms based on graphene derivatives and conducting polymers (CPs), alternatively deposited or co-deposited on the working electrode (usually a glassy carbon electrode; GCE) using a simple potentiostatic method (often cyclic voltammetry; CV), possibly followed by the deposition of metallic nanoparticles (NPs) on the electrode surface (ES). These materials have been successfully used to detect an extended range of biomolecules of clinical interest, such as uric acid (UA), dopamine (DA), ascorbic acid (AA), adenine, guanine, and others. The most common method is electrochemical synthesis. In the composites, which are often combined with metallic NPs, the interaction between the graphene derivatives-including graphene oxide (GO), reduced graphene oxide (RGO), or graphene quantum dots (GQDs)-and the CPs is usually governed by non-covalent functionalization through π-π interactions, hydrogen bonds, and van der Waals (VW) forces. The functionalization of GO, RGO, or GQDs with CPs has been shown to speed up electron transfer during the oxidation process, thus improving the electrochemical response of the resulting sensor. The oxidation mechanism behind the electrochemical response of the sensor seems to involve a partial charge transfer (CT) from the analytes to graphene derivatives, due to the overlapping of π orbitals.

Overoxidation of Intrinsically Conducting Polymers

Intrinsically conducting polymers may undergo significant changes of molecular structure and material properties when exposed to highly oxidizing conditions or very positive electrode potentials, commonly called overoxidation. The type and extent of the changes depend on the experimental conditions and chemical environment. They may proceed already at much lower rates at lower electrode potentials because some of the processes associated with overoxidation are closely related to more or less reversible redox processes employed in electrochemical energy conversion and electrochromism. These changes may be welcome for some applications of these polymers in sensors, extraction, and surface functionalization, but in many cases, the change of properties affects the performance of the material negatively, contributing to material and device degradation. This report presents published examples, experimental observations, and their interpretations in terms of both structural and of material property changes. Options to limit and suppress overoxidation are presented, and useful applications are described extensively.

Quantitative determination of uric acid using paper-based biosensor modified with graphene oxide and 5-amino-1,3,4-thiadiazole-2-thiol

Uric acid is the primary end product of human purine metabolism and has been regarded as a key parameter in urine and blood for monitoring physiological conditions. This paper presents a paper-based biosensor for a quantitative determination of uric acid using electrochemical detection. The working electrode of the biosensor is modified with graphene oxide (GO) and 5-amino-1,3,4-thiadiazole-2-thiol (ATT) by electropolymerizing ATT on the surface of graphene oxide. In this study, cyclic voltammetry (CV) measurements required only 200 μL of analyte solution. The experimental results showed that the oxidation peak current increased as the concentration of uric acid become higher and exhibited a linear relationship in the concentration range of 0.1-10 mM, indicating that this proposed biosensor has high sensitivity. In addition, this biosensor has good selectivity to detect uric acid because ATT has a specific binding with it. In human blood and body fluids, nitrites may be the only factor that can interfere with the detection of uric acid using this proposed biosensor. Nevertheless, uric acid can be discriminated from nitrite in the CV measurement due to different oxidation potentials. Thus, this proposed paper-based biosensor is a promising tool for detecting uric acid in biological samples.

Construction of Electrochemical and Photoelectrochemical Sensing Platform Based on Porphyrinic Metal-Organic Frameworks for Determination of Ascorbic Acid

Highly sensitive and specific detection of biomolecular markers is of great importance to the diagnosis and treatment of related diseases. Herein, Cu-TCPP@MOFs thin films were synthesized with tetrakis(4-carboxyphenyl) porphyrin (H₂TCPP) as organic ligands and copper ions as metal nodes. The as-synthesized Cu-TCPP@MOFs thin films as electrode modifiers were used to modify the pre-treated glassy carbon electrode (GCE) and the electrochemical performances of Cu-TCPP@MOFs/GCE were evaluated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Furthermore, as the working electrode, the constructed Cu-TCPP@MOFs/GCE was used for the investigation of ascorbic acid (AA) due to its outstanding electrocatalytic activities towards AA by several electrochemical methods, including cyclic voltammetry (CV), differential pulse voltammetry (DPV), and chronoamperometry (CA). The well-linear relationship was established based on different AA concentration ranges and the ideal detection limits (LOD) were obtained in the above-mentioned electrochemical methods, respectively. Furthermore, a Cu-TCPP MOFs@GCE sensing platform was used as a photoelectrochemical (PEC) sensor to quantitatively detect AA based on the strong absorption properties of Cu-TCPP ingredients in Cu-TCPP MOFs in a visible light band of 400~700 nm. PEC sensing platform based on Cu-TCPP@MOFs exhibited a more extensive linear concentration range, more ideal detection limit, and better sensitivity relative than the other electrochemical methods for AA. The well linear regression equations were established between the peak current intensity and AA concentrations in different electrochemical technologies, including CV, DPV, and CA, and PEC technology. AA concentration ranges applicable to various electrochemical equations were as follows: 0.45~2.10 mM of CV, 0.75~2.025 mM of DPV, 0.3~2.4 mM of CA, 7.5~480 μM of PEC, and the corresponding detection limits for AA were 1.08 μM (S/N = 3), 0.14 μM (S/N = 3), 0.049 μM (S/N = 3), and 0.084 nA/μM. Moreover, the proposed Cu-TCPP MOFs@GCE electrochemical and photoelectrochemical sensing platform was applied to determine the AA concentration of a real human serum sample; the results reveal that Cu-TCPP MOFs@GCE sensing platform could accurately determine the concentration of AA of the human serum under other potential interferences contained in the human serum samples.

Achievements of Graphene and Its Derivatives Materials on Electrochemical Drug Assays and Drug-DNA Interactions

Graphene, emerging as a true two-dimensional (2D) material, has attracted increasing attention due to its unique physical and electrochemical properties such as high surface area, excellent conductivity, high mechanical strength, and ease of functionalization and mass production. The entire scientific community recognizes the significance and potential impact of graphene. Electrochemical detection strategies have advantages such as being simple, fast, and low-cost. The use of graphene as an excellent interface for electrode modification provides a promising way to construct more sensitive and stable electrochemical (bio)sensors. The review presents sensors based on graphene and its derivatives for electrochemical drug assays from pharmaceutical dosage forms and biological samples. Future perspectives in this rapidly developing field are also discussed. In addition, the interaction of several important anticancer drug molecules with deoxyribonucleic acid (DNA) that was immobilized onto graphene-modified electrodes has been detailed in terms of dosage regulation and utility purposes.

Cobalt Ferrite Nanocomposite as Electrochemical Sensor for The Detection of Guanine, Uric Acid and Their Mixture

Cobalt ferrite nanocomposite was synthesized and characterized by analytical techniques such as FESEM, EDS and XRD. The average crystallite size was found to be in the range of 10–12 nm with a cubic structure. Further, the nanocomposite was used for the detection of guanine (GU) and uric acid (UA) and found to be an efficient electrode modifier. The lower limit of detection for GU and UA was found to be 300 nM and 400 nM, respectively

Simultaneous determination of guanine and adenine in human saliva with graphite sparked screen-printed electrodes

Saliva represents one of the most useful biological samples for non-invasive testing of health status and diseases prognosis and therefore, the development of advanced sensors enabling the determination of biomarkers in unspiked human whole saliva is of immense importance. Herein, we report on the development of a screen-printed graphite sensor modified with carbon nanomaterials generated by spark discharge for the determination of guanine and adenine in unspiked human whole saliva. The designed sensor was developed with a "green", extremely simple, fast (16 s), fully automated "linear mode" sparking process implemented with a 2D positioning device. Carbon nanomaterial-modified surfaces exhibit outstanding electrocatalytic properties enabling the determination of guanine and adenine over the concentration range 5 - 1000 nM and 25 - 1000 nM, while achieving limits of detection (S/N 3) as low as 2 nM and 8 nM, respectively. The sensor was successfully applied to the determination of purine bases in unspiked human whole saliva following a simple assay protocol based on ultrafiltration that effectively alleviates biofouling issues. Recovery was 96-108%.

Preparation of high-quality graphene oxide-carbon quantum dots composites and their application for electrochemical sensing of uric acid and ascorbic acid

Graphene oxide-quantum dots systems are emerging as a new class of materials that hold promise for biochemical sensing applications. In this paper, the eco-friendly carbon quantum dots (CQDs) are prepared with cheap and recyclable coke powders as carbon source. The graphene oxide-carbon quantum dots (GO-CQDs) composites are synthesized using graphene oxide as the conductive skeleton to load the CQDs by a one-step calcination method. The obtained GO-CQDs composites demonstrate the successful decoration of CQDs on GO nanosheets. The CQDs acting as spacers create gaps between GO sheets, resulting in a high surface area, which electively increases the electrolyte accessibility and electronic transmission. The electrocatalytic activity and reversibility of GO-CQDs composites can be effectively enhanced by tuning the mass ratio of GO to CQDs and the heating process. Furthermore, a highly sensitive and selective electrochemical sensor for determining uric acid (UA) and ascorbic acid (AA) was developed by modifying GO-CQDs composites onto a glassy carbon electrode. The results show that the linear range, minimum detection limit, and sensitivity of the GO-CQDs electrode for UA detection are 1-150 μM, 0.01 μM, and 2319.4 μA mM^-1 cm^-2, respectively, and those for AA detection are 800-9000 μM, 31.57 μM, and 53.1 μA mM^-1 cm^-2, respectively. The GO-CQDs are employed as the electrode materials for the serum and urine samples electrochemical sensing, the results indicate that the sensor can be used for the analysis of real biological samples.

Hydrogen peroxide assisted synthesis of sulfur quantum dots for the detection of chromium (VI) and ascorbic acid

Sulfur quantum dots (SQDs), heavy-metal-free quantum dots, are regarded as the next generation promising green nanomaterials compared with traditional heavy-metal-based quantum dots. However, there have been few reports on the synthesis and application of SQDs for analytical detection. Herein, an H₂O₂-assisted top-down method is used to synthesize SQDs. The as-obtained SQDs have good water dispersion, stability, photoluminescence (PL) properties and achieving a quantum yield (QY) to 11%. After adding Cr (VI) in SQDs, the fluorescence intensity decreases base on inner filter effect (IFE). Moreover, Cr (VI) can be reduced to Cr(III) when ascorbic acid (AA) is introduced into the SQDs - Cr (VI) system, accompanying the recovery of the fluorescence intensity. The fluorescence sensor displays high sensitivity and quickly response toward Cr (VI) and AA in a range of 10-120 μmol L^-1 and 20-500 μmol L^-1 with a detection limit of 0.36 μmol L^-1 and 1.21 μmol L^-1, respectively. In addition, the fluorescence sensor has been applied for the determination of Cr (VI) and AA in real samples.

A multilayer microfluidic paper coupled with an electrochemical platform developed for sample separation and detection of dopamine

A new construction of a multilayer electrochemical microfluidic paper-based analytical device using a single drop of the sample solution was performed for highly selective detection of dopamine in the presence of ascorbic acid interference.

Selective and simultaneous sensing of ascorbic acid, dopamine and uric acid based on nitrogen-doped mesoporous carbon

Development of novel sensing nanostructures for facile, economical and fast applications has attracted more and more interest. Herein, a nitrogen-doped mesoporous carbon (NMC) was synthesized by pyrolyzing a mixture of melamine and carbon black at a low-temperature (600 °C) and exploited for the simultaneous sensing of ascorbic acid (AA), dopamine (DA) and uric acid (UA). The as-made NMC exhibits a rougher surface and smaller size than carbon black. Such a one-pot method is very versatile, quick and inexpensive, easy to handle (solvent-, catalyst-, and template-free) and scalable. The oxidation potentials of the NMC/GCE negatively shift and the current responses are enhanced greatly towards the oxidation of AA, DA and UA thanks to the large surface area, mesoporous structure and N-doped active sites. The peak to peak potential separations are 258 and 410 mV for AA-DA and AA-UA. The linear ranges of AA, DA and UA are 5-4500 μM, 0.005-35 μM and 0.5-3500 μM, respectively, and their detection limits are 0.15 μM (AA), 1.6 nM (DA) and 0.15 μM (UA). Meanwhile, the NMC/GCE exhibits satisfactory stability and anti-interference ability. These results show that NMC could be a promising candidate material for electrochemical sensor construction.

Electrodeposited poly(3,4-ethylenedioxythiophene) doped with graphene oxide for the simultaneous voltammetric determination of ascorbic acid, dopamine and uric acid

Poly(3,4-ethylenedioxythiophene) (PEDOT) films were electrodeposited by cyclic voltammetry on a glassy carbon electrode (GCE) in aqueous solution. Three kinds of supporting electrolytes were used, viz. graphene oxide (GO), phosphate buffered saline (PBS), and GO in PBS, respectively. The surface morphology of the modified electrodes was characterized by scanning electron microscopy. The electrochemical performance of the modified electrodes was investigated by cyclic voltammetry and electrochemical impedance spectroscopy by using the hexacyanoferrate redox system. The results demonstrate that the PEDOT-GO/GCE, which was electropolymerized in aqueous solutions containing EDOT and GO, shows the best electrochemical activities compared with other modified electrodes. The electrochemical behaviors of ascorbic acid (AA), dopamine (DA) and uric acid (UA) were investigated by cyclic voltammetry. The PEDOT-GO/GCE exhibits enhanced electrocatalytic activities towards these important biomolecules. Under physiological pH conditions and in the mixed system of AA, DA and UA, the modified GCE exhibits the following figures of merit: (a) a linear voltammetric response in the concentration ranges of 100-1000 μM for AA, 6.0-200 μM for DA, and 40-240 μM for UA; (b) well separated oxidation peaks near 31, 213 and 342 mV (vs. saturated Ag/AgCl) for AA, DA and UA, respectively; and (c) detection of limits (at S/N = 3) of 20, 2.0 and 10 μM. The results demonstrate that GO, based on its relatively large number of anionic sites, can be used as the sole weak electrolyte and charge balance dopant for the preparation of functionally doped conducting polymers by electrodeposition. Graphical abstractSchematic representation of a nanostructure composed of hybrid conducting polymer PEDOT-GO nanocomposites, and its application to simultaneous determination of ascorbic acid, dopamine and uric acid.

Copper Nanowires Modified with Graphene Oxide Nanosheets for Simultaneous Voltammetric Determination of Ascorbic Acid, Dopamine and Acetaminophen

Copper nanowires (Cu NWs) were modified with graphene oxide (GO) nanosheets to obtain a sensor for simultaneous voltammetric determination of ascorbic acid (AA), dopamine (DA) and acetaminophen (AC). The nanocomposite was obtained via sonication, and its structures were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). The electrochemical oxidation activity of the materials (placed on a glassy carbon electrode) was studied by cyclic voltammetry and differential pulse voltammetry. Due to the synergistic effect of Cu NWs and GO, the specific surface, electrochemical oxidation performance and conductivity are improved when compared to each individual component. The peaks for AA (-0.08 V), DA (+0.16 V), and AC (+0.38 V) are well separated. The sensor has wide linear ranges which are from 1-60 μM, 1-100 μM, and 1-100 μM for AA, DA, and AC, respectively, when operated in the differential pulse voltammetric mode. The detection limits are 50, 410 and 40 nM, respectively. Potential interferences by uric acid (20 μM), glucose (10 mM), NaCl (1 mM), and KCl (1 mM) were tested for AA (1 μΜ), DA (1 μΜ), and AC (1 μΜ) and were found to be insignificant. The method was successfully applied to the quantification of AA, DA, and AC in spiked serum samples.

Construction of multifunctional electrochemical sensor based on electroactivity-adjustable poly (ionic liquids)/reduced graphene oxide

In this article, a novel electroactivity-adjustable poly (ionic liquids)/reduced graphene oxide (PIL-GP) was developed and utilized for the fabrication of multifunctional, high stable electrochemical sensors. The structure, morphology and surface charge properties of PIL-GP have been systematically studied. And the selective detection performance of dopamine (DA) on PIL-GP modified glassy carbon electrode (GCE) were further explored by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). More importantly, by virtue of the anion exchange property of PIL, electroactive Fe(CN)₆^3-/PIL-GP/GCE and Polyoxometalates (PWA)/PIL-GP/GCE were easily fabricated and their electrochemical detection performance of ascorbic acid (AA) and bromate were investigated respectively. The results showed that PIL-GP/GCE based electrochemical sensors provided higher sensitivity, lower detection limits and outstanding anti-interference ability in certain detection system. It was indicated that this general approach to construct electroactivity-adjustable sensors with various electroactive anions possessed a broad application prospect.

Nanosized iron telluride for simultaneous nanomolar voltammetric determination of dopamine, uric acid, guanine and adenine

Herein, an efficient electrochemical sensor based on nano-sized iron telluride material (FeTe₂) have been developed for the first time for simultaneous nanomolar determination of dopamine, uric acid, guanine and adenine molecules.

A review on graphene-based nanocomposites for electrochemical and fluorescent biosensors

Biosensors with high sensitivity, selectivity and a low limit of detection, reaching nano/picomolar concentrations of biomolecules, are important to the medical sciences and healthcare industry for evaluating physiological and metabolic parameters.

A ZIF-8 derived nitrogen-doped porous carbon and nitrogen-doped graphene nanocomposite modified electrode for simultaneous determination of ascorbic acid, dopamine and uric acid

Simultaneous electrochemical detection of ascorbic acid, dopamine and uric acid by a nanocomposite modified electrode was realized.

Selective response of dopamine on 3-thienylphosphonic acid modified gold electrode with high antifouling capability and long-term stability

In this work, an Au electrode modified with self-assembled monolayers (SAMs) of 3-thienylphosphonic acid (TPA) was used as a novel functional interface to selectively sense dopamine (DA) in the presence of excess ascorbic acid (AA). Ellipsometry, X-ray photoelectron spectroscopic (XPS) and electrochemical measurements proved the immobilization of TPA on the gold surface. Interestingly, the Au electrode modified with TPA substantially improved the antifouling and renewal capabilities towards the oxidation of dopamine (DA) after 15 days of storage in undeoxygenated phosphate buffer solution (PBS pH 7.4). Moreover, the TPA-SAMs modified Au electrode could afford a selective electrochemical response for the DA oxidation in the presence of ascorbic acid (AA). Based on this result, a high sensitive detection limit of 2.0 × 10^-7 M for DA could be obtained in the presence of high concentration of AA.