Sensitive and selective electrochemical aptasensing method for the voltammetric determination of dopamine based on AuNPs/PEDOT-ERGO nanocomposites

In this study, the effects of phosphate buffered saline (PBS) and graphene oxide (GO) as supporting electrolytes and dopants on the electropolymerization process of 3,4-ethylenedioxythiophene (EDOT) on glassy carbon electrode (GCE) were investigated. It was found that the PEDOT-ERGO nanocomposites obtained by a simple one-step electrochemical redox polymerization method using GO as the only supporting electrolyte and dopant possess excellent electrochemical properties. Then, the PEDOT-ERGO nanocomposites were used as electrode substrate to further modify with AuNPs, and an electrochemical aptasensor based on AuNPs/PEDOT-ERGO nanocomposites was successfully constructed for the sensitive and selective determination of dopamine (DA). Comparison of the cyclic voltammetric response of different neurotransmitters before and after aptamer assembly showed that the aptamer significantly improved the selectivity of the sensor for DA. The low detection limit of 1.0 μM (S/N = 3) indicated the good electrochemical performance of the PEDOT-ERGO nanocomposite film. Moreover, the aptasensor showed good recoveries in 50-fold diluted fetal bovine serum with RSD values all less than 5 % (n = 5), indicating that the PEDOT-ERGO nanocomposites and the electrochemical aptasensor have promising applications in other neurochemicals assay and biomedical analysis.

Electrochemical detection of redox molecules secreted by Pseudomonas aeruginosa - Part 2: Enhanced detection owing to PEDOT:PSS electrode structuration

Fast bacterial detection and identification is a crucial challenge in order to improve our antibiotics use and reduce the antimicrobial resistance. Electroanalysis of biological fluids is cheap and can be done in situ but the electrode material needs to be perfectly chosen. We previously studied electrochemical signature of Pseudomonas aeruginosa's secretome, thanks to glassy carbon electrode. Some conductive polymers are particularly efficient for biological use because of their antifouling properties, biocompatibility and way of processing. In this paper, we described the fabrication, characterization and utilisation of PEDOT:PSS film to detect and identify Pseudomonas aeruginosa through three of its secreted molecules: pyocyanin, Pseudomonas quinolone PQS and 2'-aminoacetophenone. The electrochemical responses, clearly amplified by PEDOT:PSS, can be used to identify these bacteria quickly and efficiently.

Electrochemical determination of acetamiprid using PEDOT sensing coating functionalized with carbon quantum dots and Prussian blue nanoparticles

A dual-mode electrochemical biosensor for acetamiprid detection was proposed for the first time based on carbon quantum dots/Prussian blue (CQDs/PB)-functionalized poly(3,4-ethylenedioxythiphene) (PEDOT) nanocomposite. The nanocomposite with spherical stacking nanostructure showed high surface area, excellent catalytic ability, and cycling stability. The biosensor can be effortlessly constructed after the immobilization of acetamiprid aptamer. The concentration of acetamiprid can be determined by differential pulse voltammetry (DPV) based on its signal change deduced from the pristine PB. With the capture of acetamiprid, the response current (I-T) signal generated by hydrogen peroxide catalysis from the biosensor can also been used to establish the method for monitoring acetamiprid. The dual-mode biosensor showed a wide linear range from 10^-12 g mL^-1 to 10^-6 g mL^-1, low detection limits of 6.84 × 10^-13 g mL^-1 and 4.99 × 10^-13 g mL^-1, and ultrafast detection time of 25 s and 5 s through DPV and I-T mode, respectively. The biosensor possessed excellent selectivity and stability. More importantly, the biosensor was successfully applied to detect acetamiprid residues in vegetables, proving a promising approach for routine detection of pesticide in real samples. The biosensor based on PEDOT/CQDs/PB for acetamiprid can be effortlessly constructed through both the increase of differential pulse voltammetry (DPV) signal change deduced by the pristine PB and the decrease of the response current (I-T) signal of the reduction of hydrogen peroxide catalyzed by PEDOT/CQDs/PB.

Electrochemical aptasensor based on electrodeposited poly(3,4-ethylenedioxythiophene)-graphene oxide coupled with Au@Pt nanocrystals for the detection of 17β-estradiol

An electrochemical aptasensor is reported for the sensitive and specific monitoring of 17β-estradiol (E2) based on the modification of electrodeposited poly(3,4-ethylenedioxythiophene) (PEDOT)-graphene oxide (GO) coupled with Au@Pt nanocrystals (Au@Pt). With excellent conductivity, chemical stability and active sites, the PEDOT-GO nanocomposite film was firstly in situ polymerized on the glassy carbon electrode by cyclic voltammetry. Subsequently, one-step synthesized Au@Pt were decorated on the conductive polymer, providing a platform for immobilizing the aptamer and enhancing the detecting sensitivity. With the addition of E2, since the interfacial electron transfer process was retarded by the E2-aptamer complex, the differential pulse voltammetry signal decreased gradually. Under optimum conditions, the calibration curve of E2 exhibited a linear range between 0.1 pM and 1 nM, with a low detection limit (S/N = 3) of 0.08 pM. The developed aptasensor showed admiring selectivity, stability, and reproducibility. It was tested in human serum, lake water and tap water samples after low-cost and simple pretreatment. Consequently, the developed platform could provide a new design thought for ultrasensitive detection of E2 in clinical and environmental samples.

Non-Enzymatic Glucose Sensors Involving Copper: An Electrochemical Perspective

Non-enzymatic glucose sensors based on the use of copper and its oxides have emerged as promising candidates to replace enzymatic glucose sensors owing to their stability, ease of fabrication, and superior sensitivity. This review explains the theories of the mechanism of glucose oxidation on copper transition metal electrodes. It also presents an overview on the development of among the best non-enzymatic copper-based glucose sensors in the past 10 years. A brief description of methods, interesting findings, and important performance parameters are provided to inspire the reader and researcher to create new improvements in sensor design. Finally, several important considerations that pertain to the nano-structuring of the electrode surface is provided.

Electrochemical Sensors Based on Conducting Polymers for the Aqueous Detection of Biologically Relevant Molecules

Electrochemical sensors appear as low-cost, rapid, easy to use, and in situ devices for determination of diverse analytes in a liquid solution. In that context, conducting polymers are much-explored sensor building materials because of their semiconductivity, structural versatility, multiple synthetic pathways, and stability in environmental conditions. In this state-of-the-art review, synthetic processes, morphological characterization, and nanostructure formation are analyzed for relevant literature about electrochemical sensors based on conducting polymers for the determination of molecules that (i) have a fundamental role in the human body function regulation, and (ii) are considered as water emergent pollutants. Special focus is put on the different types of micro- and nanostructures generated for the polymer itself or the combination with different materials in a composite, and how the rough morphology of the conducting polymers based electrochemical sensors affect their limit of detection. Polypyrroles, polyanilines, and polythiophenes appear as the most recurrent conducting polymers for the construction of electrochemical sensors. These conducting polymers are usually built starting from bifunctional precursor monomers resulting in linear and branched polymer structures; however, opportunities for sensitivity enhancement in electrochemical sensors have been recently reported by using conjugated microporous polymers synthesized from multifunctional monomers.

Amperometric determination of Myo-inositol using a glassy carbon electrode modified with nanostructured copper sulfide

A method for the amperometric determination of Myo-inositol is presented. Nanostructured copper sulfide material was synthesized by solvothermal method and utilized as sensor matrix. The physico-chemical analysis using XRD, Raman, FE-SEM, TEM, and XPS confirmed the formation of CuS material. The voltammetric response of CuS-modified glassy carbon electrode for a successive Myo-inositol (0.5 μM) addition confirmed that the reaction takes place at the surface of the electrode. The modified electrode resulted in signal enhancement for a linear response ranging from 0.5-8.5 μM at an applied overpotential of 0.65 V with a correlation coefficient value (R²) of 0.99. The sensitivity and limit of detection of the modified electrode were 7.87 μA μM^-1 cm^-2 and 0.24 μM, respectively. The interfering effect of various compounds present in real samples was examined. Graphical abstract Schematic representation of synthetic protocol of nanostructured CuS and Myo-inositol oxidation on CuS-modified glassy carbon electrode in basic medium.

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.

A Cu2O/Cu/carbon cloth as a binder-free electrode for non-enzymatic glucose sensors with high performance

An electrode prepared via potentiostatic electrochemical deposition exhibits a 60 nM detection limit and a 1 linear range of 1 to 1555 μM.

Phytic acid doped poly(3,4-ethylenedioxythiophene) modified with copper nanoparticles for enzymeless amperometric sensing of glucose

A nanocomposite consisting of phytic acid (PA) that was doped with poly(3,4-ethylenedioxy-thiophene) (PEDOT) and modified with copper nanoparticles (CuNPs) was placed on a glassy carbon electrode and then applied in an enzymeless glucose sensor. The undulating PEDOT/PA composite has good conductivity and a large surface area, which was suitable as substrate for the uniform growth of CuNPs. The modified electrode typically operated at a potential near 0.55 V (vs. Ag/AgCl) demonstrated remarkable catalytic activity towards direct oxidation of glucose in NaOH solution (the major limitation of this sensor). Figures of merit include (a) a wide analytical range (5 to 403 μM); (b) high sensitivity (79.27 μA·μM^-1·cm^-2), (c) a low detection limit (0.28 μM at a signal to noise ratio of 3), and (d) fast response (< 4 s). Graphical abstractA nanocomposite of phytic acid (PA) doped poly(3,4-ethylenedioxy-thiophene) (PEDOT) modified with copper nanoparticles (CuNPs) onto a glassy carbon electrode was prepared by electrochemical strategy. The CuNPs/PEDOT/PA-modified electrodes were applied in enzymeless glucose sensors with high performance.

Facile synthesis of core-shell CuS-Cu2S based nanocomposite for the high-performance glucose detection

Glucose detection is of great importance for the medical diagnosis, food biotechnology and pharmaceutical analysis. In this study, we synthesized a core-shell CuS-Cu₂S decorated carbon nanotube-graphene nanocomposite via a facile hydrothermal method. It exhibits great sensing performance towards glucose with wide linear range ranging from 0.001 to 2 mM, ultra-sensitivity of 1923 μA·cm^-2·mM^-1 and 0.33 μM detection limit in alkaline solutions. The excellent electrocatalytic activity originates from the synergistic effect between heterogeneous copper sulfides structures and carbon nanomaterials. Besides, the fabricate sensor also has great durability, selectivity and great potential for practical applications.

Colorimetric and Ratiometric Fluorescence Dual-Mode Sensing of Glucose Based on Carbon Quantum Dots and Potential UV/Fluorescence of o-Diaminobenzene

A novel colorimetric and ratiometric fluorescence sensor was constructed by using carbon quantum dots (CQDs) and o-diaminobenzene (ODB). Unlike ODB by itself, ODB oxide (oxODB) not only emits fluorescence, but also produces ultraviolet (UV) absorption. Therefore, on the basis of the potential optical properties of ODB, glucose oxidase (Gox) and horseradish peroxidase (HRP) were introduced into a CQDs⁻ODB system for the quantitative oxidation of ODB. When glucose is present, it is oxidized by oxygen under the catalytic action of its oxidase to form hydrogen peroxide. Hydrogen peroxide is a strong oxidant that can rapidly oxidize ODB through the catalysis of horseradish peroxidase. oxODB can cause changes in the fluorescence ratio (I550/I446) and absorbance ratio (A/A₀). At the same time, the color of the detection solution can also change under sunlight and ultraviolet lamps. Therefore, glucose can be quantitatively detected by ratiometric fluorescence and colorimetry simultaneously, and semi-quantitatively detected by observing the colors with sunlight and ultraviolet lamps of 365 nm. This increases not only the convenience but also the accuracy of detection. In addition, this sensor has good selectivity and can be used for the determination of glucose in serum, providing a new idea for the development of blood glucose sensors.

Simultaneous determination of isoproterenol, acetaminophen, folic acid, propranolol and caffeine using a sensor platform based on carbon black, graphene oxide, copper nanoparticles and PEDOT:PSS

We explored the use of carbon black (CB), graphene oxide (GO), copper nanoparticles (CuNPs) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) as electrode materials for the simultaneous determination of isoproterenol, acetaminophen, folic acid, propranolol and caffeine. The designed nanostructured surface was widely characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), contact angle measurements and electrochemistry. From electrochemical characterization assays carried out towards the potassium ferricyanide redox probe, fast electron transfer kinetics and a considerably higher electroactive surface area were observed for the modified electrodic surface based on CB, GO, CuNPs and PEDOT:PSS film. Using square-wave voltammetry (SWV), well defined and resolved anodic peaks were detected for isoproterenol, acetaminophen, folic acid, propranolol and caffeine, with peak-to-peak potential separation not less than 170 mV. Then, the SWV technique was explored for the simultaneous determination of quinary mixtures of these analytes, resulting in analytical curves with linear ranges and limits of detection at micromolar concentration levels. The practical viability of the proposed voltammetric sensor was illustrated in the analysis of human body fluid samples. The proposed sensor showed good repeatability and a successful application using urine and serum matrices, with recoveries close to 100%.

Reduced graphene oxide-supported methylene blue nanocomposite as a glucose oxidase-mimetic for electrochemical glucose sensing

A novel electrochemical glucose sensor based on methylene blue-reduced graphene oxide nanocomposite was constructed, and the sensor exhibited good glucose oxidase-mimetic electrocatalytic activity towards glucose and practical applicability.

Nanomaterial-doped conducting polymers for electrochemical sensors and biosensors

This review summarizes recent advances in the development of electrochemical sensors and biosensors based on nanomaterial doped conducting polymers.

Graphene paper supported MoS2 nanocrystals monolayer with Cu submicron-buds: High-performance flexible platform for sensing in sweat

Flexible sweat biosensors are of considerable current interest for the development of wearable smart miniature devices. In this work, we report a novel type of flexible and electrochemical sweat platform fabricated by depositing Cu submicron buds on freestanding graphene paper (GP) carrying MoS₂ nanocrystals monolayer for bio-functional detection of glucose and lactate. Quantitative analysis of glucose and lactate was carried out by using amperometric i-t method. Linear ranges were obtained between 5 and 1775 μM for glucose and 0.01-18.4 mM for lactate, and their corresponding limits of detection were 500 nM and 0.1 μM, respectively. The platform demonstrates fast response, good selectivity, superb reproducibility and outstanding flexibility, which enable its use for monitoring glucose and lactate in human perspiration. The strategy of structurally integrating 3D transition metal, 0D transition metal sulfide and 2D graphene will provide new insight into the design of flexible electrodes for sweat glucose and lactate monitoring and a wider range of applications in biosensing, bioelectronics, and lab-on-a-chip devices.

Development of a PrGO-Modified Electrode for Uric Acid Determination in the Presence of Ascorbic Acid by an Electrochemical Technique

An attractive electrochemical sensor of poly(3,4-ethylenedioxythiophene)/reduced graphene oxide electrode (PrGO) was developed for an electrochemical technique for uric acid (UA) detection in the presence of ascorbic acid (AA). PrGO composite film showed an improved electrocatalytic activity towards UA oxidation in pH 6.0 (0.1 M PBS). The PrGO composite exhibited a high current signal and low charge transfer resistance (Rct) compared to a reduced graphene oxide (rGO) electrode or a bare glassy carbon electrode (GCE). The limit of detection and sensitivity of PrGO for the detection of UA are 0.19 μM (S/N = 3) and 0.01 μA/μM, respectively, in the range of 1-300 μM of UA.

Studies on electrochemical glucose sensing, antimicrobial activity and cytotoxicity of fabricated copper nanoparticle immobilized chitin nanostructure

In this study, copper nanoparticle immobilized chitin nanocomposite (CNP/CuNP) was synthesized and used for the development of non-enzymatic electrochemical sensor. The CNP/CuNP was characterized by X-ray diffraction (XRD), fourier transform infra red (FTIR) spectroscopy and high resolution transmission electron microscopy (HRTEM) analysis. The glucose sensing property of CNP/CuNP was investigated by cyclic voltammetry (CV) and chronoamperometry (CA). As a result of the synergistic effect of CNP and CuNP, the modified electrode displayed effective electro-oxidation of glucose in 0.1M NaOH solution. At 0.45V potential the modified electrode showed response towards glucose in the linear range of 1-1000μM with a lowest detection limit of 0.776μM with better selectivity and stability. In addition, the antimicrobial activity of CNP/CuNP was evaluated against bacterial and fungal strains. CNP/CuNP displayed enhanced antimicrobial activity when compared to CNP and CuNP alone. Similarly, cytotoxicity of CNP/CuNP was tested against Artemia salina, which showed no toxic effect in the tested concentration.

A controllable honeycomb-like amorphous cobalt sulfide architecture directly grown on the reduced graphene oxide–poly(3,4-ethylenedioxythiophene) composite through electrodeposition for non-enzyme glucose sensing

A facile, controllable two-step electrodeposition route was developed, whereby a honeycomb-like amorphous Co_xS_y architecture was obtained via direct growth on rGO–PEDOT/GCE as an electrode for glucose detection.

Microwave synthesis of 3D rambutan-like CuO and CuO/reduced graphene oxide modified electrodes for non-enzymatic glucose detection

Illustration of the glucose biosensing mechanism based on CuO/r-GO composites.

Electrodeposition of a 3D hierarchical porous flower-like cobalt–MWCNT nanocomposite electrode for non-enzymatic glucose sensing

A versatile and cost-effective electrodeposition technique was adopted to synthesize cobalt and cobalt–MWCNT nanocomposite electrodes and the fabricated cobalt–MWCNT material was successfully demonstrated as a non-enzymatic glucose sensor.