Simultaneous determination of catecholamines, uric acid and ascorbic acid at physiological levels using poly(N-methylpyrrole)/Pd-nanoclusters sensor

An interesting electrochemical sensor has been constructed by the electrodeposition of palladium nanoclusters (Pd_nano) on poly(N-methylpyrrole) (PMPy) film-coated platinum (Pt) electrode. Cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy were used to characterize the properties of the modified electrode. It was demonstrated that the electroactivity of the modified electrode depends strongly on the electrosynthesis conditions of the PMPy film and Pd_nano. Moreover, the modified electrode exhibits strong electrocatalytic activity toward the oxidation of a mixture of dopamine (DA), ascorbic acid (AA), and uric acid (UA) with obvious reduction of overpotentials. The simultaneous analysis of this mixture at conventional (Pt, gold [Au], and glassy carbon) electrodes usually struggles. However, three well-resolved oxidation peaks for AA, DA, and UA with large peak separations allow this modified electrode to individually or simultaneously analyze AA, DA, and UA by using differential pulse voltammetry (DPV) with good stability, sensitivity, and selectivity. This sensor is also ideal for the simultaneous analysis of AA, UA and either of epinephrine (E), norepinephrine (NE) or l-DOPA. Additionally, the sensor shows strong electrocatalytic activity towards acetaminophen (ACOP) and other organic compounds. The calibration curves for AA, DA, and UA were obtained in the ranges of 0.05 to 1 mM, 0.1 to 10 μM, and 0.5 to 20 μM, respectively. The detection limits (signal/noise [S/N] = 3) were 7 μM, 12 nM, and 27 nM for AA, DA, and UA, respectively. The practical application of the modified electrode was demonstrated by measuring the concentrations of AA, DA, and UA in injection sample, human serum, and human urine samples, respectively, with satisfactory results. The reliability and stability of the modified electrode gave a good possibility for applying the technique to routine analysis of AA, DA, and UA in clinical tests.     

Detection of glucose using immobilized bienzyme on cyclic bisureas–gold nanoparticle conjugate

A highly sensitive electrochemical glucose sensor has been developed by the co-immobilization of glucose oxidase (GOx) and horseradish peroxidase (HRP) onto a gold electrode modified with biocompatible cyclic bisureas–gold nanoparticle conjugate (CBU–AuNP). A self-assembled monolayer of mercaptopropionic acid (MPA) and CBU–AuNP was formed on the gold electrode through a layer-by-layer assembly. This modified electrode was used for immobilization of the enzymes GOx and HRP. Both the HRP and GOx retained their catalytic activity for an extended time, as indicated by the low value of Michaelis–Menten constant. Analytical performance of the sensor was examined in terms of sensitivity, selectivity, reproducibility, lower detection limit, and stability. The developed sensor surface exhibited a limit of detection of 100 nM with a linear range of 100 nM to 1 mM. A high sensitivity of 217.5 μA mM⁻¹ cm⁻² at a low potential of −0.3 V was obtained in this sensor design. Various kinetic parameters were calculated. The sensor was examined for its practical clinical application by estimating glucose in human blood sample.     

Electrochemical DNA biosensor based on silver nanoparticles/poly(3-(3-pyridyl) acrylic acid)/carbon nanotubes modified electrode

In this work, we present an electrochemical DNA sensor based on silver nanoparticles/poly(trans-3-(3-pyridyl) acrylic acid) (PPAA)/multiwalled carbon nanotubes with carboxyl groups (MWCNTs-COOH) modified glassy carbon electrode (GCE). The polymer film was electropolymerized onto MWCNTs-COOH modified electrode by cyclic voltammetry (CV), and then silver nanoparticles were electrodeposited on the surface of PPAA/MWCNTs-COOH composite film. Thiol group end single-stranded DNA (HS-ssDNA) probe was easily covalently linked onto the surface of silver nanoparticles through a 5′ thiol linker. The DNA hybridization events were monitored based on the signal of the intercalated adriamycin by differential pulse voltammetry (DPV). Based on the response of adriamycin, only the complementary oligonucleotides gave an obvious current signal compared with the three-base mismatched and noncomplementary oligonucleotides. Under the optimal conditions, the increase of reduction peak current of adriamycin was linear with the logarithm of the concentration of the complementary oligonucleotides from 9.0 × 10⁻¹² to 9.0 × 10⁻⁹ M with a detection limit of 3.2 × 10⁻¹² M. In addition, this DNA sensor exhibited an excellent reproducibility and stability during DNA hybridization assay.     

Preparation of a manganese titanate nanosensor: Application in electrochemical studies of captopril in the presence of para-aminobenzoic acid

This study reports the synthesis and characterization of a novel nanostructure-based electrode for electrochemical studies and determination of captopril (CP). At first manganese titanate nanoceramics were synthesized by the sol–gel method. The structural evaluations of the pure nanopowders were investigated by different techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Then it was used to prepare a new nanostructured manganese titanate carbon paste electrode (MnTiO₃/CPE). The characterization of the modified sensor was carried out by comprehensive techniques such as electrochemical impedance spectroscopy (EIS), SEM, and voltammetry. Subsequently, the modified electrode was used for CP catalytic oxidation in the presence of para-aminobenzoic acid (PABA) as a mediator. The results showed that PABA has high catalytic activity for CP oxidation. The electrochemical behavior of CP was studied by cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CHA), and differential pulse voltammetry (DPV) techniques. Under the optimized conditions, the catalytic oxidation peak current of CP showed two linear dynamic concentration ranges of 1.0 × 10⁻⁸ to 1.0 × 10⁻⁷ and 1.0 × 10⁻⁷ to 1.0 × 10⁻⁶, with a detection limit of 1.6 nM (signal/noise = 3), using the DPV technique. Finally, the proposed method was successfully applied for determination of CP in pharmaceutical and biological samples.     

Highly sensitive electrochemical aptasensor for immunoglobulin E detection based on sandwich assay using enzyme-linked aptamer

Here, we describe the fabrication of an electrochemical immunoglobulin E (IgE) aptasensor using enzyme-linked aptamer in the sandwich assay method and thionine as redox probe. In this protocol, 5′-amine-terminated IgE aptamer and thionine were covalently attached on glassy carbon electrode modified with carbon nanotubes/ionic liquid/chitosan nanocomposite. Furthermore, another IgE aptamer was modified with biotin and enzyme horseradish peroxidase (HRP), which attached to the aptamer via biotin–streptavidin interaction. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry were performed at each stage of the chemical modification process to confirm the resulting surface changes. The presence of IgE induces the formation of a double aptamer sandwich structure on the electrode, and the electrocatalytic reduction current of thionine in the presence of hydrogen peroxide was measured as the sensor response. Under optimized conditions and using differential pulse voltammetry as the measuring technique, the proposed aptasensor showed a low detection limit (6 pM) and high sensitivity (1.88 μA nM⁻¹). This aptasensor also exhibited good stability and high selectivity for IgE detection without an interfering effect of some other proteins such as bovine serum albumin (BSA) and lysozyme. The application of the aptasensor for IgE detection in human serum sample was also investigated. The proposed protocol is quite promising as an alternative sandwich approach for various protein assays.     

Voltammetric behavior of complexation of salbutamol with calf thymus DNA and its analytical application

The interaction of salbutamol (Sal), an animal growth promoter, with DNA was investigated by differential pulse voltammetry (DPV), cyclic voltammetry (CV), and fluorescence spectroscopy. An irreversible reduction was observed from the cyclic voltammograms, and the reaction mechanism involved a one-electron change irreversible oxidation. In the presence of DNA, the DPV peak current decreased and the Sal peak shifted to higher potentials, indicating that Sal interacted with DNA to form an intercalation Sal–DNA complex. In addition, reaction binding parameters were extracted from the DPV data with the use of the multivariate curve resolution–alternating least squares (MCR–ALS) method; the binding constant and ratio were found to be (2.0 ± 0.5) × 10⁵ M⁻¹ and 1:1, respectively. Quantitative voltammetric analysis of Sal was performed in the concentration range of 3.02 × 10⁻⁶ to 1.23 × 10⁻⁴ mol L⁻¹, and it was found that the detection limit was 5.11 × 10⁻⁷ mol L⁻¹ in the presence of 1.00 × 10⁻⁶ mol L⁻¹ DNA. The method was applied for the determination of Sal in spiked urine and human serum samples, and the calibration was successfully verified.     

A highly sensitive nanostructure-based electrochemical sensor for electrocatalytic determination of norepinephrine in the presence of acetaminophen and tryptophan

A new electrochemical sensor for the determination of norepinephrine (NE), acetaminophen (AC) and tryptophan (Trp) is described. The sensor is based on carbon paste electrode (CPE) modified with 3,4-dihydroxybenzaldehyde-2,4-dinitrophenylhydrazone (DDP) and takes the advantages of carbon nanotubes (CNTs), which makes the modified electrode highly sensitive for the electrochemical detection of these compounds. Cyclic voltammetry (CV) at various scan rates was used to investigate the redox properties of the modified electrode. The apparent charge transfer rate constant, k(s), and transfer coefficient, α, for electron transfer between DDP and CNT paste electrode were calculated. The mediated oxidation of NE at the modified electrode was investigated by CV and the values of k, α and diffusion coefficient (D) were calculated. Under the optimum pH of 7.0, the oxidation of NE occurs at a potential about 215 mV less positive than that of the unmodified CPE. Differential pulse voltammetry (DPV) of NE at the modified electrode exhibited two linear dynamic ranges with a detection limit (3σ) of 77±2 nM. DPV was used for simultaneous determination of NE, AC and Trp at the modified electrode, and quantitation of NE in some real samples by the standard addition method.     

DNA immobilization on a polypyrrole nanofiber modified electrode and its interaction with salicylic acid/aspirin

A double-stranded calf thymus DNA (dsDNA) was physisorbed onto a polypyrrole (PPy) nanofiber film that had been electrochemically deposited onto a Pt electrode. The surface morphology of the polymeric film was characterized using scanning electron microscopy (SEM). The electrochemical characteristics of the PPy film and the DNA deposited onto the PPy modified electrode were investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). Then the interaction of DNA with salicylic acid (SA) and acetylsalicylic acid (ASA), or aspirin, was studied on the electrode surface with DPV. An increase in the DPV current was observed due to the oxidation of guanine, which decreased with the increasing concentrations of the ligands. The interactions of SA and ASA with the DNA follow the saturation isotherm behavior. The binding constants of these interactions were 1.15 × 10⁴ M for SA and 7.46 × 10⁵ M for ASA. The numbers of binding sites of SA and ASA on DNA were approximately 0.8 and 0.6, respectively. The linear dynamic ranges of the sensors were 0.1–2 μM (r² = 0.996) and 0.05–1 mM (r² = 0.996) with limits of detection of 8.62 × 10⁻¹ and 5.24 × 10⁻⁶ μM for SA and ASA, respectively.     

Study of interactions between DNA and aflatoxin B1 using electrochemical and fluorescence methods

In this study, a carbon paste electrode modified with N-butylpyridinium hexafluorophosphate (BPPF₆) ionic liquid and DNA was introduced as an electrochemical biosensor to study the interaction between DNA and aflatoxin B1 molecules. For this purpose, variations in oxidation peak current of guanine in various concentrations of aflatoxin B1 were measured by using the differential pulse voltammetry (DPV) method. According to this study, the binding constant of DNA–aflatoxin B1 was found to be 3.5 × 10⁶ M⁻¹. This modified electrode was also used for determination of low concentrations of aflatoxin B1 by using differential pulse voltammetry. A linear dynamic range from 8.00 × 10⁻⁸ to 5.91 × 10⁻⁷ M and a limit of detection of 2.00 × 10⁻⁸ M resulted from DPV measurements. To confirm our results, a fluorescence study was also performed. It resulted in a binding constant of 2.8 × 10⁶ M⁻¹, which is in good agreement with that obtained from electrochemical study.     

Electrochemical assay for the determination of nitric oxide metabolites using copper(II) chlorophyllin modified screen printed electrodes

This work presents a novel electrochemical assay for the collective measurement of nitric oxide (NO) and its metabolites nitrite (NO₂⁻) and nitrate (NO₃⁻) in volume miniaturized sample at low cost using copper(II) chlorophyllin (CuCP) modified sensor electrode. Zinc oxide (ZnO) incorporated screen printed carbon electrode (SPCE) was used as a host matrix for the immobilization of CuCP. The morphological changes of the ZnO and CuCP modified electrodes were investigated using scanning electron microscopy. The electrochemical characterization of CuCP–ZnO–SPCE exhibited the characteristic quasi-reversible redox peaks at the potential +0.06 V versus Ag/AgCl. This biosensor electrode showed a wide linear range of response over NO concentrations from 200 nM to 500 μM with a detection limit of 100 nM and sensitivity of 85.4 nA μM⁻¹. Furthermore, NO₂⁻ measurement showed linearity of 100 nM to 1 mM with a detection limit of 100 nM for NO₂⁻ and sensitivity of 96.4 nA μM⁻¹. Then, the concentration of NO₃⁻ was measured after its enzymatic conversion into NO₂⁻. Using this assay, the concentrations of NO, NO₂⁻, and NO₃⁻ present in human plasma samples before and after beetroot supplement were estimated using suitable membrane coated CuCP–ZnO–SPCE and validated with the standard Griess method.     

An electrochemical sensor based on cellulose nanocrystal for the enantioselective discrimination of chiral amino acids

A novel electrochemical sensor based on 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanocrystals (TOCNCs) and l-cystines (l-Cys) modified Au electrode (TOCNC/l-Cys/Au) has been fabricated for detection and discrimination of the enantiomers of phenylalanine (Phe), leucine (Leu), and valine (Val). The three amino acids are in connection with metabolism diseases. The TOCNC/l-Cys/Au electrode exhibited obvious peak current difference for the amino acid enantiomers by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The TOCNCs on the electrode surface expressed different interactions with d- and l-amino acids, so the electrochemical recognitions of the three amino acid enantiomers were achieved. TOCNCs were characterized by Fourier transform infrared (FT-IR) and scanning electron microscopy (SEM). The modified electrodes were characterized by SEM and electrochemical techniques. According to DPV, peak currents of the two enantiomers decreased linearly with their concentrations. Furthermore, satisfactory results were obtained when this electrode was applied to measure the d- and l-Phe mixture. The experimental results show that TOCNCs are suitable material for chiral sensor. The contrast of serum sample of healthy people and patients with type 2 diabetes also was proposed, and significant difference was exhibited on the modified electrode. This work is significant for the screening, diagnosis, and treatment of multiple metabolic diseases.     

Sex determination based on amelogenin DNA by modified electrode with gold nanoparticle

We have developed a simple and renewable electrochemical biosensor based on carbon paste electrode (CPE) for the detection of DNA synthesis and hybridization. CPE was modified with gold nanoparticles (AuNPs), which are helpful for immobilization of thiolated bioreceptors. AuNPs were characterized by scanning electron microscopy (SEM). Self-assembled monolayers (SAMs) of thiolated single-stranded DNA (SH–ssDNA) of the amelogenin gene was formed on CPE. The immobilization of the probe and its hybridization with the target DNA was optimized using different experimental conditions. The modified electrode was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The electrochemical response of ssDNA hybridization and DNA synthesis was measured using differential pulse voltammetry (DPV) with methylene blue (MB) as an electroactive indicator. The new biosensor can distinguish between complementary and non-complementary strands of amelogenin ssDNA. Genomic DNA was extracted from blood and was detected based on changes in the MB reduction signal. These results demonstrated that the new biosensor could be used for sex determination. The proposed biosensor in this study could be used for detection and discrimination of polymerase chain reaction (PCR) products of amelogenin DNA.     

Ultrasensitive DNA sensor based on gold nanoparticles/reduced graphene oxide/glassy carbon electrode

We have designed a simple and novel electrochemical biosensor based on glassy carbon electrode (GCE) for DNA detection. GCE was modified with reduced graphene oxide (RGO) and gold nanoparticles (AuNPs) by the electrochemical method, which is helpful for immobilization of thiolated bioreceptors. The electrode modification processes were characterized by scanning electron microscopy (SEM) and electrochemical methods. Then a single-stranded DNA (ssDNA) probe for BRCA1 5382 insC mutation detection was immobilized on the modified electrode for a specific time. The experimental conditions, such as probe immobilization time and target DNA (complementary DNA) hybridization time and temperature with probe DNA, were optimized using electrochemical methods. The electrochemical response for DNA hybridization and synthesis was measured using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) methods. The calibration graph contains two linear ranges; the first part is in the range of 3.0 × 10⁻²⁰ to 1.0 × 10⁻¹² M, and the second segment part is in the range of 1.0 × 10⁻¹² to 1.0 × 10⁻⁷ M. The biosensor showed excellent selectivity for the detection of the complementary sequences from noncomplementary sequences, so it can be used for detection of breast cancer.     

Biosensor based on the biocatalysis of microperoxidase-11 in nanocomposite material of multiwalled carbon nanotubes/room temperature ionic liquid for amperometric determination of hydrogen peroxide

A novel nanocomposite material of multiwalled carbon nanotubes (MWCNTs) and room temperature ionic liquid (RTIL) N-butylpyridinium hexafluorophosphate (BPPF₆) was explored and used to construct a novel microperoxidase-11 (MP-11) biosensor for the determination of hydrogen peroxide (H₂O₂). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to characterize the performance of the biosensor. Under the optimized experimental conditions, H₂O₂ could be detected in a linear calibration range of 0.5 to 7.0 × 10⁻⁷ mol L⁻¹ with a correlation coefficient of 0.9949 (n = 9) and a detection limit of 3.8 × 10⁻⁹ mol L⁻¹ at 3σ. The modified electrodes displayed excellent electrochemical response, high sensitivity, long-term stability, and good bioactivity and selectivity.     

An electrochemical DNA biosensor based on gold nanorods decorated graphene oxide sheets for sensing platform

A simple electrochemical sensor for sensitive and selective DNA detection was constructed based on gold nanorods (Au NRs) decorated graphene oxide (GO) sheets. The high-quality Au NRs–GO nanocomposite was synthesized via the electrostatic self-assembly technique, which is considered a potential sensing platform. Differential pulse voltammetry was used to monitor the DNA hybridization event using methylene blue as an electrochemical indicator. Under optimal conditions, the peak currents of methylene blue were linear with the logarithm of the concentrations of complementary DNA from 1.0 × 10⁻⁹ to 1.0 × 10⁻¹⁴ M with a detection limit of 3.5 × 10⁻¹⁵ M (signal/noise = 3). Moreover, the prepared electrochemical sensor can effectively distinguish complementary DNA sequences in the presence of a large amount of single-base mismatched DNA (1000:1), indicating that the biosensor has high selectivity.     

An ultrasensitive supersandwich electrochemical DNA biosensor based on gold nanoparticles decorated reduced graphene oxide

In this article, a supersandwich-type electrochemical biosensor for sequence-specific DNA detection is described. In design, single-strand DNA labeled with methylene blue (MB) was used as signal probe, and auxiliary probe was designed to hybridize with two different regions of signal probe. The biosensor construction contained three steps: (i) capture DNA labeled with thiol was immobilized on the surface of gold nanoparticles decorated reduced graphene oxide (Au NPs/rGO); (ii) the sandwich structure formation contained “capture–target–signal probe”; and (iii) auxiliary probe was introduced to produce long concatamers containing signal molecule MB. Differential pulse voltammetry (DPV) was used to monitor the DNA hybridization event using peak current changes of MB in phosphate-buffered saline (PBS) containing 1.0 M NaClO₄. Under optimal conditions, the peak currents of MB were linear with the logarithm of the concentration of target DNA in the range of 0.1 μM to 0.1 fM with a detection limit of 35 aM (signal/noise = 3). In addition, this biosensor exhibited good selectivity even for single-base mismatched target DNA detection.     

Nafion/lead nitroprusside nanoparticles modified carbon ceramic electrode as a novel amperometric sensor for l-cysteine

This work describes the electrochemical and electrocatalytic properties of carbon ceramic electrode (CCE) modified with lead nitroprusside (PbNP) nanoparticles as a new electrocatalyst material. The structure of deposited film on the CCE was characterized by energy dispersive X-ray (EDX), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM). The cyclic voltammogram (CV) of the PbNP modified CCE showed two well-defined redox couples due to [Fe(CN)₅NO]³⁻/[Fe(CN)₅NO]²⁻ and Pb^IV/Pb^II redox reactions. The modified electrode showed electrocatalytic activity toward the oxidation of l-cysteine and was used as an amperometric sensor. Also, to reduce the fouling effect of l-cysteine and its oxidation products on the modified electrode, a thin film of Nafion was coated on the electrode surface. The sensor response was linearly changed with l-cysteine concentration in the range of 1 × 10⁻⁶ to 6.72 × 10⁻⁵ mol L⁻¹ with a detection limit (signal/noise ratio [S/N] = 3) of 0.46 μM. The sensor sensitivity was 0.17 μA (μM)⁻¹, and some important advantages such as simple preparation, fast response, good stability, interference-free signals, antifouling properties, and reproducibility of the sensor for amperometric determination of l-cysteine were achieved.     

Voltammetric discrimination of mandelic acid enantiomers

We report a novel electrochemical biosensor for direct discrimination of d- and l-mandelic acid (d- and l-MA) in aqueous medium. The glassy carbon electrode (GCE) surface was modified with reduced graphene oxide (rGO) and γ-globulin (GLOB). Electrochemical characterization of the modified electrodes was investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The modified electrode surfaces were also characterized by scanning electron microscopy. Electrochemical response of the prepared electrode (GCE/rGO/GLOB) for discrimination of d- and l-MA enantiomers was investigated by cyclic voltammetry and was compared with bare GCE in the concentration range of 2 to 10 mM. Whereas the bare GCE showed no electrochemical response for the MA enantiomers, the GCE/rGO/GLOB electrode exhibited direct and selective discrimination with different oxidation potential values of 1.47 and 1.71 V and weak reduction peaks at potential values of −1.37 and −1.48 V, respectively. In addition, electrochemical performance of the modified electrode was investigated in mixed solution of d- and l-MA. The results show that the produced electrode can be used as electrochemical chiral biosensor for MA.     

A lactate biosensor based on lactate dehydrogenase/nictotinamide adenine dinucleotide (oxidized form) immobilized on a conducting polymer/multiwall carbon nanotube composite film

An amperometric lactate biosensor was developed based on a conducting polymer, poly-5,2′-5′,2′′-terthiophene-3′-carboxylic acid (pTTCA), and multiwall carbon nanotube (MWNT) composite on a gold electrode. Lactate dehydrogenase (LDH) and the oxidized form of nicotinamide adenine dinucleotide (NAD⁺) were subsequently immobilized onto the pTTCA/MWNT composite film. The modified electrode was characterized by quartz crystal microbalance (QCM), scanning electron microscopy (SEM), and electrochemical experiments. The detection signal was amplified by the pTTCA/MWNT assembly onto which a sufficient amount of enzyme was immobilized and stabilized by the covalent bond formation between the amine groups of enzyme and the carboxylic acid groups of the pTTCA/MWNT film. Experimental parameters affecting the sensor responses, such as applied potential, pH, and temperature, were assessed and optimized. Analytical performances and dynamic ranges of the sensor were determined, and the results showed that the sensitivity, stability, and reproducibility of the sensor improved significantly using pTTCA/MWNT composite film. The calibration plot was linear (r² = 0.9995) over the range of 5 to 90 μM. The sensitivity was approximately 0.0106 μA/μM, with a detection limit of 1 μM, based on a signal/noise ratio of 3. The applicability of the sensor for the analysis of l-lactate concentration in commercial milk and human serum samples was demonstrated successfully.     

Application of a Cu–chitosan/multiwalled carbon nanotube film-modified electrode for the sensitive determination of rutin

A new sensitive electrochemical sensor, a glassy carbon electrode modified with chemically cross-linked copper-complexed chitosan/multiwalled carbon nanotubes (Cu–CS/MWCNT/GCE), for rutin analysis was constructed. Experimental investigations of the influence of several parameters showed that the rutin can effectively accumulate on the surface of the Cu–CS/MWCNT/GCE, which accumulation caused a pair of well-defined redox peaks in the electrochemical signal when measurements were carried out in Britton–Robinson buffer solution (pH 3, 0.04 M). The surface of the Cu–CS/MWCNT/GCE was characterized by field-emission scanning electron microscopy, transmission electron microscopy, and X-ray diffractometry analysis. In a rutin concentration range of 0.05–100 μM and under optimized conditions, a linear relationship between the oxidation peak current of rutin and its concentration was obtained with a detection limit of 0.01 μM. The Cu–CS/MWCNT/GCE showed good selectivity, stability, and reproducibility. Moreover, the sensor was used to determine the presence of rutin in fruits with satisfactory results.