Electrochemical copper (II) sensor based on self-assembled 4-amino-6-hydroxy-2-mercaptopyrimidine monohydrate

A 4-amino-6-hydroxy-2-mercaptopyrimidine monohydrate (AHMP)-based self-assembled monolayer (SAM) was formed on the gold electrode surface. Ellipsometric measurements evidenced the SAM formation on the gold electrode surface. The structural integrity of the modified gold electrode was also characterized by insulating properties of the SAM that were detected by cyclic voltammetry. The results of cyclic voltammetry showed that the SAM, which was formed by assembly of AHMP, was stable but did not completely block the redox-activity of ferrocene and K₃[Fe(CN)₆]/K₄[Fe(CN)₆]. In contrast completely blocked redox-activity was observed after the treatment of AHMP-based SAM with saturated solution of 4-formylphenylboronic acid in 1,4-dioxan. The modified electrodes exhibited a selective response towards Cu(II) ions in the presence of some interfering ions such as Cd(II), Co(II), Fe(II), Ni(II) and Pb(II). This study is the first scientific report on the application of AHMP-modified electrode as a selective Cu(II) sensor in the presence of some interfering cations.     

Aptamer biosensor for label-free impedance spectroscopy detection of thrombin based on gold nanoparticles

This paper presents a simple electrochemical impedance spectroscopy (EIS) aptasensor based on an anti-thrombin-aptamer as a molecular recognition element. Improvement in sensitivity was achieved by utilizing gold nanoparticles (AuNPs), which were self-assembled on the surface of a bare electrode by using 1,6-Hexanedithiol as a medium. To quantify the amount of thrombin, changes in the interfacial electron transfer resistance (R_et) of the aptasensor were monitored using the redox couple of an [Fe(CN)₆]^3−/4− probe. The plot of (Reti−Ret₀)/Ret₀ against the logarithm of thrombin concentration is linear with over the range from 0.1 nM to 30 nM with a detection limit of 0.013 nM. Meanwhile, the packing density of aptamers was determined by cyclic voltammetric (CV) studies of redox cations (e.g., [Ru(NH₃)₆]³⁺) which were electrostatically bound to the DNA phosphate backbones. The results indicate that the total amount of aptamer probes immobilized on the gold nanoparticle surface is sixfold higher than that on the bare electrode. The aptasensor also showed good selectivity for thrombin without being affected by the presence of other proteins.     

基于抗体包被纳米金和铜配合物共固定修饰电极的癌胚抗原安培免疫传感器研究

研制了基于抗体包被化学镀纳米金(AuNPs)和[Cu(bpy)2(ONO)]NO3配合物(CuL)共固定修饰玻碳电极(GCE)的安培免疫传感器,并用于血清中癌胚抗原(CEA)的检测。首先将GCE电极表面氧化形成羧基,进而键合上乙二胺。将此胺化电极浸泡在CuL和化学镀金溶液后,CuL可通过π-π堆积作用吸附到GCE表面,并在电极表面还原成30~50nm的纳米金层(GCE|CuL/AuNPs)。将上述电极浸泡在CEA抗体(anti CEA)溶液中,利用AuNPs固定anti CEA,并通过辣根过氧化物酶(HRP)封闭剩余的AuNPs位点,由此构建了一类快速检测CEA的无试剂安培免疫传感器(GCE|CuL-AuNPs/anti CEA-HRP)。其中CuL作为电子媒介体对过氧化脲(CP)有催化还原作用,而且HRP可增强这种作用。当该传感器在37℃下,含CEA的pH6.5PBS溶液中温育30min后,随着温育液中CEA浓度的增加,电极表面形成的免疫复合物也增加,导致CuL对CP的催化电流下降。电流下降百分比1%与CEA浓度在0.1~80ng/mL之间成线性关系,检测限为0.052ng/mL(3σ)。由于采用化学镀法可...     

A novel amperometric biosensor for oxalate determination using multi-walled carbon nanotube-gold nanoparticle composite

An amperometric oxalate biosensor using nanohybrid film of multi-walled carbon nanotubes (MWCNTs) and gold colloidal nanoparticles (GNPs) via carbodiimide chemistry by forming amide linkages between carboxylic acid groups on the CNTs and amine residues of cysteamine self-assembled monolayer (SAM) has been prepared. The c-MWCNTs were immobilized on the gold (Au) electrode and characterized by FTIR. The morphologies of the c-MWCNT/Au and GNPs/MWCNT/Au electrodes were investigated by scanning electron microscopy (SEM) and the electrochemical performance of the Au, c-MWCNT/Au and GNPs/c-MWCNT/Au electrodes were also studied amperometrically. The Cl⁻ and NO₃⁻ insensitive oxalate oxidase from grain sorghum was finally immobilized on this electrode. The influence of pH, temperature and oxalate concentration on electrode activity was studied. The electrode showed optimum response within 7 s. The electrocatalytic response showed a linear dependence on the oxalic acid concentration ranging from 1 to 800 μM with a detection limit of 1 μM. The K_m value for the oxalic acid sensor was 444.44 μM. The enzyme electrode retained 30% of its initial activity after 5 months, when stored at 4 °C. The electrode was employed for measurement of oxalic acid in serum, urine and foodstuffs.     

The electrochemical method for detecting 26S proteasome

Detection of 26S proteasome, a multiproteolytic complex that degrades intracellular proteins in eukaryotic cells, by electrochemical methods is of interest for improved understanding of living cells and detection of cancer. This study develops an electrochemical system to detect 26S using a gold electrode modified by a self-assembled monolayer of 1,6-hexanedithiol (HDT) for capture of 26S proteasomes. When 26S is fixed on a HDT-gold electrode, it is found that electrolyte anions can enhance detection but also cause damage to the HDT layer. Cyclic voltammetry and electrochemical impedance spectroscopy demonstrate that HDT stability is better in LiClO₄ solution than in sodium sulfate (Na₂SO₄) solution. Chymotrypsin-like activity of 26S as measured by fluorescence with Suc-LLVY-AMC substrate declines 10% with LiClO₄ and 25% with Na₂SO₄. LiClO₄ is a better electrolyte salt in a 26S-HDT-gold electrode application in Tris buffer. Increased electron transfer resistance is observed after binding 26S on the HDT-gold electrode. Stable 26S concentration is from 2 to 100 nM. As 26S concentration increases from 2 to 100 nM, the electron-transfer impedance of Fe(CN)₆^4−/3− redox rises logarithmically. The range of electrochemical detection of 26S proteasome is nanomolar.     

基于抗体包被金磁纳米微粒修饰的磁性安培免疫传感器研制及对人血清癌抗原19-9的检测

在金电极表面修饰壳聚糖(CS)膜,并在酸性pH下利用CS上形成的-NH3+静电吸引Fe(CN)]3-6-(FeCN)到电极表面,制成了在pH 6.5磷酸盐缓冲液(PBS)中具有电活性的Au | CS-FeCN电极;再通过外加磁场吸引,在Au | CS-FeCN表面修饰一层血清癌抗原19-9单克隆抗体(anti CA19-9)包被的金磁纳米微粒(Fe3O4(核)／Au(壳),简称GMP),由此构建了一类快速检测CA19-9的无试剂安培免疫传感器(Au| CS-FeCN／GMP-anti CA19-9).用扫描电镜(SEM),X-射线荧光光谱(XFS)和X-射线光电子能谱(XPS)对电极表面进行了表征;并采用循环伏安法(CV),示差脉冲伏安法(DPV)、交流阻抗法(E1S)分 别研究了该传感器的电化学性质和对CAl9-9的检测性能.实验表明:Au I CS-FeCN／GMP-anti CAl9-9电极在含CAl9-9的pH 6.5 PBS中于35℃下温育25 min,其DPV还原电流下降值(AI)与CA19-9在0.1～10 U／mL和10~50 U／mL范围内成正比,检出下限为0.056 U／mL(3d).用于血清样本检测并和标准ELISA方法对照,结果一致.只需移去外加磁场,用PBS清洗电极表面即可实现电极更新.该磁性免疫传感器集分离、富集和测定于一身,灵敏度高、稳定性好、表面易更新,有望用于人血清中痕量CA19-9的快速检测.     

Impedimetric immunosensor for electronegative low density lipoprotein (LDL) based on monoclonal antibody adsorbed on (polyvinyl formal)-gold nanoparticles matrix

Monoclonal antibodies (MAb) have been commonly applied to measure LDL in vivo and to characterize modifications of the lipids and apoprotein of the LDL particles. The electronegative low density lipoprotein (LDL⁻) has an apolipoprotein B-100 modified at oxidized events in vivo. In this work, a novel LDL⁻ electrochemical biosensor was developed by adsorption of anti-LDL⁻ MAb on an (polyvinyl formal)-gold nanoparticles (PVF-AuNPs)-modified gold electrode. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to characterize the recognition of LDL⁻. The interaction between MAb-LDL⁻ leads to a blockage in the electron transfer of the [Fe(CN)₆]⁴⁻/K₄[Fe(CN)₆]³⁻ redox couple, which may could result in high change in the electron transfer resistance (R_CT) and decrease in the amperometric responses in CV analysis. The compact antibody-antigen complex introduces the insulating layer on the assembled surface, which increases the diameter of the semicircle, resulting in a high R_CT, and the charge transferring rate constant κ⁰ decreases from 18.2 × 10⁻⁶ m/s to 4.6 × 10⁻⁶ m/s. Our results suggest that the interaction between MAb and lipoprotein can be quantitatively assessed by the modified electrode. The PVF-AuNPs-MAb system exhibited a sensitive response to LDL⁻, which could be used as a biosensor to quantify plasmatic levels of LDL⁻.     

A label-free amperometric immunosensor based on horseradish peroxidase functionalized carbon nanotubes and bilayer gold nanoparticles

In this work, a novel label-free amperometric immunosensor has been constructed for detecting α-1-fetoprotein (AFP) based on nanocomposite of horseradish peroxidase (HRP) labeled carbon nanotubes (CNTs). First, the gold nanoparticles (AuNPs) were electrodeposited on the surface of the glass carbon electrode by electrochemical reduction of gold chloride tetrahydrate (HAuCl₄) to immobilize horseradish peroxidase labeled carbon nanotubes (HRP-CNTs). Then HRP-CNTs bioconjugate was immobilized on the surface of the electrodeposited AuNPs layer by the combination of forces (coordination and electrostatic force). Subsequently, it was immersed into gold colloidal nanoparticles (GNPs) solution, which was used to immobilize antibody biomolecules (anti-AFP). Enhanced sensitivity was obtained by using bioconjugates featuring HRP labeled (HRP-CNTs), which had lager specific surface area and good electronic catalysis (current response signal) compared to carbon nanotubes. Under optimized conditions, the linear ranges were from 0.2 to 200 ng mL⁻¹ with a detection limit of 0.067 ng mL⁻¹ (at an S/N of 3). The proposed immunosenor showed good precision, acceptable stability and reproducibility and could be used for the detection AFP in normal human serum, which provided a potential alternative tool for the detection of protein in clinical diagnosis.     

Gold nanoparticles-coated eggshell membrane with immobilized glucose oxidase for fabrication of glucose biosensor

This work reports the fabrication and application of a glucose biosensor based on the catalytic effect of gold nanoparticles (AuNPs) on enzymatic reaction for blood glucose determination. AuNPs were initially in situ synthesized on the surface of an eggshell membrane (ESM) which was subsequently immobilized with glucose oxidase (GO_x) to produce a GO_x-AuNPs/ESM. The GO_x-AuNPs/ESM was positioned on the surface of an oxygen electrode to form a GO_x-AuNPs/ESM glucose biosensor. The effects of pH, concentration of phosphate buffer solution and amount of GO_x on the response of the GO_x-AuNPs/ESM glucose biosensor were studied in detail. AuNPs on GO_x/ESM can improve the calibration sensitivity (30% higher than GO_x/ESM without AuNPs), stability (87.3% of its initial response to glucose after 10-week storage) and shortens the response time (<30 s) of the glucose biosensor. The linear working range for the GO_x-AuNPs/ESM glucose biosensor is 8.33 μM to 0.966 mM glucose with a detection limit of 3.50 μM (S/N = 3). The biosensor has been successfully applied to determine the glucose in human blood serum samples and the results compared well to a standard spectrophotometric method commonly used in hospitals. Our work demonstrates that the developed GO_x-AuNPs/ESM glucose biosensor has potential in biomedical analysis.     

Potentiometric study of quinohemoprotein alcohol dehydrogenase immobilized on the carbon rod electrode

Enzymes, which exhibit redox properties and are able to directly exchange electrons with conducting materials, are currently of special interest in the fields of biosensorics and bioelectronics. The detection of new electronic properties makes them even more attractive for these growing fields. Quinohemoprotein alcohol dehydrogenase (QH-ADH) from Gluconobacter sp. 33 was demonstrated as ‘nano-sized electrical power generator’ able to separate the electrical charges and generate a measurable electrical potential. This phenomenon was investigated potentiometrically in electrochemical system where QH-ADH was applied as the catalyst oxidizing ethanol thereby converting the energy of this chemical reaction to an electrical potential. A basic immobilization technique based on cross-linking with glutaraldehyde was applied for the immobilization of QH-ADH onto a carbon rod. The maximal open circuit potential generated by QH-ADH immobilized on carbon rod electrode was −115 mV versus an inactivated QH-ADH-modified electrode (Inactiv-ADH/carbon). If 10 mM of redox mediator K₃[Fe(CN)₆] was added to the solution the potential rose to −190 mV versus Inactiv-ADH/carbon. The influence of concentration of Na acetate buffer, pH 6.0, on registered potential was approximately at the same level as the influence of KCl concentration (influence of ionic strength). This result implies that local pH changes do not play a significant role in the development of QH-ADH-modified carbon electrode potential. The potentiometric signal was more stable than amperometric signal based on the same QH-ADH-modified carbon electrode. The ability to directly generate electric potential opens new opportunities for the application of QH-ADH and other direct electron transfer exhibiting enzymes in the design of new potentiometric sensors, biofuel cells and self-powering bioelectronic devices.     

Direct electron transfer of myoglobin in mesoporous silica KIT-6 modified on screen-printed electrode

A disposable hydrogen peroxide biosensor was developed based on the direct electron transfer of myoglobin (Mb) on mesopores KIT-6 modified screen-printed electrode (SPE) which was manually performed to fabricate the planar carbon electrodes. KIT-6 is a new material which can absorb abundant of Mb molecules. A mixture of Mb and KIT-6 was immobilized with nafion on electrode. The cyclic voltammetry experiment indicated that a pair of stable and well-defined reduction peaks with a formal potentials of −0.35, and −0.28 V versus saturated calomel electrode (SCE) was obtained, using the present modified electrode in phosphate buffer saline (0.05 M, pH 7.0) at scan rate of 100 mV s⁻¹, characteristic of Mb heme Fe(III)/Fe(II) redox couple. The heterogeneous electron transfer rate constant k_s was estimated to be 16.93 s⁻¹. And the formal potential was pH-dependent, having two slopes of −54.7 and −49.3 mV/pH which illustrated one electron transfer. This modified electrode was applied to detect H₂O₂ with sensitivity of 55.68 mA M⁻¹ cm⁻². Infrared spectrum and UV–vis absorption spectra of immobilized Mb film were recorded. In conclusion, KIT-6 increases the electron transfer activity of Mb and this kind of H₂O₂ biosensor is low cost for using disposable.     

Development of molecularly imprinted electrochemical sensor with titanium oxide and gold nanomaterials enhanced technique for determination of 4-nonylphenol

4-Nonylphenol (4-NP) was reported to affect the health of wildlife and humans through altering endocrine function. A novel electrochemical sensor for sensitive and fast determination of 4-NP was developed. Titanium oxide (TiO₂) nanoparticles and gold nanoparticles (AuNPs) were introduced for the enhancement of electron conduction and sensitivity. 4-NP-imprinted functionalized AuNPs composites with specific binding sites for 4-NP was modified on electrode. The resulting electrodes were characterized by cyclic voltammetry (CV). Rebinding experiments were carried out to determine the specific binding capacity and selective recognition. The linear range was over the range from 4.80 × 10⁻⁴ to 9.50 × 10⁻⁷ mol L⁻¹, with the detection limit of 3.20 × 10⁻⁷ mol L⁻¹ (S/N = 3). The sensor was successfully employed to detect 4-NP in real samples.     

Ionic liquid and nanogold-modified immunosensing interface for electrochemical immunoassay of hepatitis B surface antigen in human serum

A mediator-free electrochemical immunoassay protocol based on a disposable immunosensor for the detection of hepatitis B surface antigen (HBsAg) in human serum was developed. To fabricate such an immunosensor, a layer of sol–gel composite film containing room temperature ionic liquid and chitosan was initially formed on a glassy carbon electrode. Nanogold particles were then adsorbed onto the membrane via the amine groups of chitosan molecules, and then horseradish peroxidase (HRP)-labeled hepatitis B surface antibodies (HRP-anti-HBs) were immobilized onto the nanogold surface. With a non-competitive immunoassay format, the antibody–antigen complex could be formed by a simple one-step immunoreaction between the immobilized HRP-anti-HBs and HBsAg in sample solution. The formed immunocomplex inhibited partly the active center of the HRP, which decreased the immobilized HRP toward the reduction of H₂O₂. The performance and factors influencing the performance of the immunosensor were evaluated. Under optimal conditions, the current change obtained from the carried HRP relative to H₂O₂ system was proportional to HBsAg concentration in the range of 1.5–400 ng/mL with a detection limit of 0.5 ng/mL (at 3δ). The reproducibility, selectivity, and stability of the proposed immunosensor were acceptable. Moreover, the proposed immunosensors were used to analyze HBsAg in human serum specimens. Analytical results of clinical samples suggested that the developed immunosensor has a promising alternative approach for detecting HBsAg in the clinical diagnosis.     

Monofunctionalized β-cyclodextrins as sensor elements for the detection of small molecules

β-Cyclodextrins functionalized by different moieties that were tethered to a single 6-deoxyaminoglucose unit were investigated with respect to their suitability for sensor applications. Derivatizing the cyclodextrins with hydrophobic moieties like dipalmitoylglycerol and cholesterol allowed us to study packing density and orientation of the cyclodextrin tori at the air–water interface. From the pressure-area isotherms, it was concluded that the cyclodextrins are positioned towards the water subphase, with their molecular axis predominately parallel to the interface. By introducing a disulfide group, we managed to immobilize cyclodextrins on gold surfaces via self-assembly. MALDI mass spectrometry (MALDI MS) and XPS confirmed that the molecules are chemisorbed on the gold substrate displaying high surface coverage as determined by means of impedance spectroscopy. The inclusion of various charged guest molecules was monitored by changes in the charge transfer resistance of the redox couple [Fe(CN)₆]³⁻/[Fe(CN)₆]⁴⁻. The charge transfer resistance is sensitive to the surface potential, which leads to either repulsion or attraction of the redox active species.     

Microfabricated electrochemical sensors for exhaustive coulometry applications

The development of microfabricated electrochemical systems suitable for deployment in sensor networks that operate with a minimum of operator intervention are of great interest; therefore, a coulometric sensing system for exhaustive coulometry with the potential for calibration-free operation has been designed, fabricated and evaluated to support such development. The sensor chips were microfabricated onto a silicon substrate and contained a variety of specially designed thin-film gold working electrodes (ranging from one to five per chip) and a Ag/AgCl pseudo-reference electrode. A custom flow cell containing fluidic connections and counter electrode chamber was also constructed to integrate the sensor and to create an electrolysis chamber with a fixed volume. Different chip designs were evaluated as exhaustive coulometric sensors in terms of reproducibility and longevity using Fe(CN)₆^3?/4? as model analytes. The relative standard deviation (RSD) for a chip tested over a period of 42 days was 5.5% whereas the sensor-to-sensor reproducibility was within 6.3%.     

Reliable new immunosensor for atrazine pesticide analysis

The aim of the present research was to develop a highly selective and sensitive amperometric immunosensor for atrazine based on a “competition” assay procedure. An immunosensor device for the determination of triazinic pesticides based on two different competition procedures is therefore described. The immunosensor developed uses an amperometric electrode for hydrogen peroxide as transducer and the peroxidase enzyme as marker. The results demonstrate the full validity of this immunosensor method which was optimized by comparing two different “competition” operating procedures. The results obtained using the new immunosensor were then compared with those found using an inhibition OPEE (Organic Phase Enzyme Electrode) for triazinic pesticide detection, which showed no selectivity toward different classes of triazinic, carbamate or organophosphate pesticides. The immunosensor developed displayed on the contrary an appreciable selectivity both toward different classes of pesticides and toward triazinic or benzotriazinic products. In addition, the K_aff value was evaluated. Lastly, the immunosensor was also used to test triazinic pesticide recovery from common real matrices such as milk and vegetal samples, obtaining good recoveries.     

Bean sprout peroxidase biosensor based on l-cysteine self-assembled monolayer for the determination of dopamine

A new bean sprout peroxidase was immobilized on a gold electrode modified with self-assembled monolayers (SAM) of l-cysteine for the determination of dopamine in pharmaceutical samples using square wave voltammetry. In the bean sprout–(SAM)–Au electrode, the peroxidase, in the presence of hydrogen peroxide, catalyzes the oxidation of dopamine to the corresponding quinone, which is electrochemically reduced back to dopamine at +0.15 V vs. Ag/AgCl. The performance and the factors influencing the response of this biosensor were studied in detail. The best performance was obtained using 0.1 mol L⁻¹ phosphate buffer solution (pH 6.0), 6.0 × 10⁻⁵ mol L⁻¹ hydrogen peroxide, frequency of 100 Hz, pulse amplitude of 80 mV and scan increment of 4.0 mV. The analytical curve was linear for dopamine concentrations from 9.91 × 10⁻⁶ to 2.21 × 10⁻⁴ mol L⁻¹ and the detection limit was 4.78 × 10⁻⁷ mol L⁻¹. The recovery of dopamine ranged from 98.0 to 111.8% and the relative standard deviation was 3.1% for a solution containing 1.30 × 10⁻⁵ mol L⁻¹ dopamine (n = 6). The lifetime of this biosensor was 15 days (at least 300 determinations). The results obtained for dopamine determination in pharmaceutical formulations using the proposed bean sprout–SAM–Au electrode were in agreement with those obtained with the standard method at the 95% confidence level.     

Fabrication of novel chitosan nanofiber/gold nanoparticles composite towards improved performance for a cholesterol sensor

A novel amperometric cholesterol biosensor was fabricated by the immobilization of ChOx (cholesterol oxidase) onto the chitosan nanofibers/gold nanoparticles (designated as CSNFs/AuNPs) composite network (NW). The fabrication involves preparation of chitosan nanofibers (CSNFs) and subsequent electrochemical loading of gold nanoparticles (AuNPs). Field emission scanning electron microscopy (FE-SEM) was used to investigate the morphology of CSNFs (sizes in the range of ∼50-100 nm) and spherical AuNPs. Cyclic voltammetry, hydrodynamic voltammetry and amperometry were used to examine the performance of CSNF-AuNPs/ChOx biosensor. The CSNF-AuNPs/ChOx biosensor exhibited a wide linear response to cholesterol (concentration range of 1-45 μM), good sensitivity (1.02 μA/μM), low response time (∼5 s) and excellent long term stability. The combined existence of AuNPs within CSNFs NW provides the excellent performance of the biosensor towards the electrochemical detection of cholesterol.     

Label-free electrochemical immunosensor for sensitive detection of kanamycin

A novel label-free electrochemical immunosensor for sensitive detection of kanamycin based on water-soluble graphene sheet (WGS)/prussian blue-chitosan (PB-CTS)/nanoporous gold (NPG) composited film has been reported. PB was selected as an electron transfer mediator, and was modified onto the electrode together with WGS through electrostatic adsorption. Then NPG was immobilized onto the as-prepared film for biomolecules anchoring. The electroactivity of PB was greatly enhanced in the presence of WGS and NPG. It could mainly be ascribed to the fact that the good conductivity of WGS and NPG promoted electron transfer and enhanced the sensitivity. kanamycin antibody, as a model, was immobilized onto the composite film for the detection of kanamycin. Under optimum conditions, the amperometric signal of PB decreased linearly with kanamycin concentration (0.02-14 ng mL⁻¹), a linear calibration plot (y = 1.3817 + 4.7544x, r = 0.9993), resulting in a low limit of detection (6.31 pg mL⁻¹). The novel immunosensor for the detection of kanamycin in real sample with satisfactory results has been proved. In addition, this method would be easily adapted for the detection of other residual antibiotics in animal derived foods.     

Nanogold based electrochemical sensor for determination of norepinephrine in biological fluids

A stable layer of gold nano particles (AuNPs) was deposited on the surface of indium tin oxide (ITO) and was used as an electrode for the detection of norepinephrine (NE) by square wave voltammetry (SWV) and cyclic voltammetry (CV). This modified electrode exhibits potent and persistent electron-mediating behavior and a well-defined oxidation peak towards NE was observed. The peak potential of NE was observed at less positive potential with increase in peak current as compared to bare ITO and bare gold electrodes. NE exhibited two quasi-reversible couples at AuNPs modified ITO over the potential range from −0.6 to 0.8 V in phosphate buffer solution (PBS) (pH 7.2). At optimal experimental condition, the catalytic oxidative peak current was responsive with the NE concentrations ranging from 100 nM to 25 μM. The detection limit was found to be 87 nM. Also, the effect of pH revealed that the oxidation of NE at the AuNPs modified ITO involved the transfer of equal number of protons and electrons. The interfering effect of common coexisting metabolites in blood and urine has also been reported. The modified electrode exhibited high stability and reproducibility. A comparison of results with high performance liquid chromatography (HPLC) signalizes a good agreement.