Evaluation of a biosensor based on reduced graphene oxide and glucose oxidase enzyme on the monitoring of second-generation ethanol production

Journal of Solid State Electrochemistry - An easily prepared biosensor based on reduced graphene oxide (rGO) and glucose oxidase (GOx) enzyme was developed to monitor the enzymatic hydrolysis...     

Amperometric lactate nanobiosensor based on reduced graphene oxide,carbon nanotube and gold nanoparticle nanocomposite

Microchimica Acta - Copper nanoclusters (CuNCs) are an attractive alternative to other metal nanoclusters. The synthesis of CuNCs is highly efficient and fast, with low-cost and without any...     

A sensitive biosensor for lactate based on layer-by-layer assembling MnO2 nanoparticles and lactate oxidase on ion-sensitive field-effect transistors

A sensitive enzyme-based FET biosensor for lactate has been obtained by introducing MnO2 nanoparticles at the gate surface via a layer-by-layer assembling method.     

Design and characterization of a lactate biosensor based on immobilized lactate oxidase onto gold surfaces

The design and characterization of a lactate biosensor and its application to the determination of this analyte in wine and beer are described. The biosensor is developed through the immobilization of lactate oxidase (LOx) using two different strategies including direct adsorption and covalent binding. The characterization of the resulting lactate oxidase monolayers was performed in aqueous phosphate buffer solutions using atomic force microscopy (AFM) and quartz crystal microbalance (QCM) techniques. In presence of lactate and using hydroxymethylferrocene as a redox mediator, biosensors obtained by either direct adsorption or by covalent binding exhibit a clear electrocatalytic activity, and lactate could be determined amperometrically at 300 mV versus SSCE. Results obtained under these conditions give a linear current response versus lactate concentration up to 0.3 mM, with a detection limit of 10 μM of lactate and a sensitivity of 0.77 ± 0.08 μA mM⁻¹. Finally, biosensors were applied to the determination of lactate in wine and beer. The results obtained are in good agreement with those obtained by a well-established enzymatic-spectrophotometric assay kit.     

Glucose biosensor based on glucose oxidase immobilized on a nanofilm composed of mesoporous hydroxyapatite, titanium dioxide, and modified with multi-walled carbon nanotubes

We report on a highly sensitive glucose biosensor that was fabricated from a composite made from mesoporous hydroxyapatite and mesoporous titanium dioxide which then were ultrasonically mixed with multi-walled carbon nanotubes to form a rough nanocomposite film. This film served as a platform to immobilize glucose oxidase onto a glassy carbon electrode. The morphological and electrochemical properties of the film were examined by scanning electron microscopy and electrochemical impedance spectroscopy. Cyclic voltammetry and chronoamperometry were used to characterize the electrochemical performances of the biosensor which exhibited excellent electrocatalytic activity to the oxidation of glucose. At an operating potential of 0.3?V and pH 6.8, the sensor displays a sensitivity of 57.0?μA?mM^?1?cm^?2, a response time of <5?s, a linear dynamic range from 0.01 to 15.2?mM, a correlation coefficient of 0.9985, and a detection limit of 2?μM at an SNR of 3. No interferences are found for uric acid, ascorbic acid, dopamine and most carbohydrates. The sensor is stable and was successfully applied to the determination of glucose in real samples.

Enzymatic glucose biosensor based on bismuth nanoribbons electrochemically deposited on reduced graphene oxide

We describe the electrochemical preparation of bismuth nanoribbons (Bi-NRs) with an average length of 100 ± 50 nm and a width of 10 ± 5 μm by a potentiostatic method. The process occurs on the surface of a glassy carbon electrode (GCE) in the presence of disodium ethylene diamine tetraacetate that acts as a scaffold for the growth of the Bi-NRs and also renders them more stable. The method was applied to the preparation of Bi-NRs incorporated into reduced graphene oxide. This nanocomposite was loaded with the enzyme glucose oxidase onto a glassy carbon electrode. The resulting biosensor displays an enhanced redox peak for the enzyme with a peak-to-peak separation of about 28 mV, revealing a fast electron transfer at the modified electrode. The loading of the GCE with electroactive GOx was calculated to be 8.54 × 10⁻¹⁰ mol∙cm⁻², and the electron transfer rate constant is 4.40 s⁻¹. Glucose can be determined (in the presence of oxygen) at a relatively working potential of −0.46 V (vs. Ag|AgCl) in the 0.5 to 6 mM concentration range, with a 104 μM lower detection limit. The sensor also displays appreciable repeatability, reproducibility and remarkable stability. It was successfully applied to the determination of glucose in human serum samples.

A potentiostatic method was used to prepare reduced graphene oxide and bismuth nanoribbons nanocomposite on a glassy carbon electrode. This nanocomposite was loaded with enzyme glucose oxidase to fabricate a glucose biosensor.

     

Effective bioelectrocatalysis of bilirubin oxidase on electrochemically reduced graphene oxide

Graphene oxide (GO) was applied for construction of an effective biocathode based on bilirubin oxidase (BOD). Separation of small-sized GO sheets together with the BOD immobilisation protocol has detrimental effects on the bioelectrocatalytic reduction of oxygen. When BOD was deposited on electrochemically reduced GO (ErGO) only a negligible current density j = 2.6 μA cm^− 2 was observed. Current density dramatically increased to a value of 46 μA cm^− 2 once BOD was in-situ mixed with as-received GO directly on a glassy carbon electrode (GCE) with subsequent electrochemical reduction of the BOD/GO composite. When this protocol was tested with small-sized GO flakes separated simply using centrifugation, the fabricated biocathode exhibited j = 120 μA cm^− 2. A current density further increased to j = 280 μA cm^− 2 when BOD and purified GO were incubated ex-situ for 4 h, followed by the BOD/GO composite collection by centrifugation, its deposition on the GCE and electrochemical reduction. Moreover, oxygen reduction current increased steeply with a steady-state current density achieved at high potential (≈ 500 mV), close to the onset potential of oxygen reduction (≈ 580 mV).     

Enhanced amperometric response of a glucose oxidase and horseradish peroxidase based bienzyme glucose biosensor modified with a film of polymerized toluidine blue containing reduced graphene oxide

Reduced graphene oxide (RGO) was used to construct a bienzyme biosensor containing horseradish peroxidase (HRP) and glucose oxidase (GOx). A poly(toluidine blue) (pTB) film containing RGO acted as both enzyme immobilization matrix and electron transfer mediator. The bienzyme biosensor was characterized by electrochemical techniques and displays a highly sensitive amperometric response to glucose and hydrogen peroxide (H₂O₂) at a potential as low as −0.1 V (vs. SCE). It is shown that use of RGO causes a strong enhancement on the amperometric responses. H₂O₂ formed by the action of GOx in the presence of oxygen can be further reduced by HRP in the pTB film contacting the RGO modified electrode. In the absence of oxygen, glucose oxidation proceeds by another mechanism in which electron transfer occurs from GOx to the electrode and with pTB acting as the mediator. Amperometric responses to glucose and H₂O₂ follow Michaelis-Menten kinetics. The experimental conditions were optimized, and under these conditions glucose can be determined in the 80 μM to 3.0 mM range with a detection limit of 50 μM. H₂O₂, in turn, can be quantified in up to 30.0 μM concentration with a detection limit of 0.2 μM. The bienzyme biosensor is reproducible, repeatable and stable. Finally, it has been successfully applied to the determination of glucose in plasma samples.

Schematic representation of glocuse detection at GCE/RGO/pTB-HRP-GOx.

     

Glucose biosensor based on immobilization of glucose oxidase in platinum nanoparticles/graphene/chitosan nanocomposite film

The bionanocomposite film consisting of glucose oxidase/Pt/functional graphene sheets/chitosan (GOD/Pt/FGS/chitosan) for glucose sensing is described. With the electrocatalytic synergy of FGS and Pt nanoparticles to hydrogen peroxide, a sensitive biosensor with a detection limit of 0.6 μM glucose was achieved. The biosensor also has good reproducibility, long-term stability and negligible interfering signals from ascorbic acid and uric acid comparing with the response to glucose. The large surface area and good electrical conductivity of graphene suggests that graphene is a potential candidate as a sensor material. The hybrid nanocomposite glucose sensor provides new opportunity for clinical diagnosis and point-of-care applications.     

Amperometric detection of nitric oxide using a glassy carbon electrode modified with gold nanoparticles incorporated into a nanohybrid composed of reduced graphene oxide and Nafion

Microchimica Acta - The authors show that the electrocatalytic performance toward the detection of nitric oxide (NO) can be enhanced by making use of gold nanoparticles (AuNP) in a matrix...     

Dopamine sensor based on a glassy carbon electrode modified with a reduced graphene oxide and palladium nanoparticles composite

We report on a sensitive electrochemical sensor for dopamine (DA) based on a glassy carbon electrode that was modified with a nanocomposite containing electrochemically reduced graphene oxide (RGO) and palladium nanoparticles (Pd-NPs). The composite was characterized by scanning electron microscopy, energy dispersive spectroscopy, and electrochemical impendence spectroscopy. The electrode can oxidize DA at lower potential (234 mV vs Ag/AgCl) than electrodes modified with RGO or Pd-NPs only. The response of the sensor to DA is linear in the 1–150 μM concentration range, and the detection limit is 0.233 μM. The sensor was applied to the determination of DA in commercial DA injection solutions.

Hollow BiOBr/reduced graphene oxide hybrids encapsulating hemoglobin for a mediator-free biosensor

Journal of Solid State Electrochemistry - For the construction of a mediator-free biosensor, hollow BiOBr microspheres (H-BiOBr MS) were hydrothermally synthesized and combined with reduced...     

Impedimetric aptasensor for Staphylococcus aureus based on nanocomposite prepared from reduced graphene oxide and gold nanoparticles

We describe here an aptasensor for the ultrasensitive detection of Staphylococcus aureus by electrochemical impedance spectroscopy (EIS). Single-stranded DNA was linked to a nanocomposite prepared from reduced graphene oxide (rGO) and gold nanoparticles (AuNP). Thiolated ssDNA was covalently linked to the AuNPs linked to rGO, and probe DNA was immobilized on the surface of an AuNP-modified glassy carbon electrode to capture and concentrate Staph. aureus. The probe DNA of the aptasensor selectively captures the target bacteria in its three-dimensional space, and these results in a dramatic increase in impedance. Scanning electron microscopy, cyclic voltammetry and EIS were used to monitor the single steps of the electrode assembly process. The effect was utilized to quantify the bacteria in the concentration range from 10 to 10⁶ cfu mL^?1 and with a detection limit of 10 cfu mL^?1 (S/N?=?3). The relative standard deviation of Staphylococcus aureus detection was equal to 4.3 % (10⁵ cfu mL^?1, n?=?7). In addition to its sensitivity, the biosensor exhibits high selectivity over other pathogens.

Electrochemical detection of reduced graphene oxide nanoparticles in aqueous solution

We have demonstrated electrochemical detection of reduced graphene oxide (rGO) nanoparticles on an ultramicroelectrode (UME) in aqueous solution using rGO collision events. The collision phenomena are detected by monitoring a current–time transient. To attract the rGO to the UME surface, a positive electric field was developed near the UME using a redox reaction. As model systems, ferrocenemethanol and ferrocyanide oxidation reactions were adopted. Amperometric current measurements showed a staircase current response after attachment of rGO on the UME surface. The magnitude of the staircase current is given by the stepwise increase in current, which can provide insight into the size distribution of the rGO colliding with the UME. In the presence of higher concentrations of rGO, multiple collision events happened sequentially on the UME. In this case, an increasing current trend, rather than a single staircase current, was observed. The overall current increment for a given time is a measure of the concentration of rGO in solution. By using this method, charged conductive materials in an aqueous solution can be sensitively detected and/or accumulated.     

Detection of Aeromonas hydrophila DNA oligonucleotide sequence using a biosensor design based on Ceria nanoparticles decorated reduced graphene oxide and Fast Fourier transform square wave voltammetry

A new strategy was introduced for ssDNA immobilization on a modified glassy carbon electrode. The electrode surface was modified using polyaniline and chemically reduced graphene oxide decorated cerium oxide nanoparticles (CeO₂NPs-RGO). A single-stranded DNA (ssDNA) probe was immobilized on the modified electrode surface. Fast Fourier transform square wave voltammetry (FFT-SWV) was applied as detection technique and [Ru(bpy)₃]^2+/3+ redox signal was used as electrochemical marker. The hybridization of ssDNA with its complementary target caused a dramatic decrease in [Ru(bpy)₃]^2+/3+ FFT-SW signal. The proposed electrochemical biosensor was able to detect Aeromonas hydrophila DNA oligonucleotide sequence encoding aerolysin protein. Under optimal conditions, the biosensor showed excellent selectivity toward complementary sequence in comparison with noncomplementary and two-base mismatch sequences. The dynamic linear range of this electrochemical DNA biosensor for detecting 20-mer oligonucleotide sequence of A. hydrophila was from 1 × 10⁻¹⁵ to 1 × 10⁻⁸ mol L⁻¹. The proposed biosensor was successfully applied for the detection of DNA extracted from A. hydrophila in fish pond water up to 0.01 μg mL⁻¹ with RSD of 5%. Besides, molecular docking was applied to consider the [Ru(bpy)₃]^2+/3+ interaction with ssDNA before and after hybridization.     

Preparation of cobalt-tetraphenylporphyrin/reduced graphene oxide nanocomposite and its application on hydrogen peroxide biosensor

A novel cobalt-tetraphenylporphyrin/reduced graphene oxide (CoTPP/RGO) nanocomposite was prepared by a π–π stacking interaction and characterized by ultraviolet–visible absorption spectroscopy (UV–vis), Fourier transform infrared spectroscopy (FTIR) and electrochemical impedance spectroscopy (EIS). The CoTPP/RGO nanocomposite exhibited high electrocatalytic activity both for oxidation and reduction of H₂O₂. The current response was linear to H₂O₂ concentration with the concentration range from 1.0 × 10⁻⁷ to 2.4 × 10⁻³ mol L⁻¹ (R = 0.998) at the reductive potential of −0.20 V and from 1.0 × 10⁻⁷ to 4.6 × 10⁻⁴ mol L⁻¹ (R = 0.996) at the oxidative potential of +0.50 V. The H₂O₂ biosensor showed good anti-interfering ability towards oxidative interferences at the oxidative potential of +0.50 V and good anti-interfering ability towards reductive interferences at the reductive potential of −0.20 V.     

Electrochemical quercetin sensor based on a nanocomposite consisting of magnetized reduced graphene oxide,silver nanoparticles and a molecularly imprinted polymer on a screen-printed electrode

An electrochemical quercetin (QR) sensor is described that is based on the use of magnetic reduced graphene oxide (MrGO) incorporated into a molecularly imprinted polymer (MIP) on the surface of a screen-printed electrode (SPE). The MrGO consists of reduced graphene oxide (rGO), magnetite (Fe₃O₄) and silver nanoparticles (Ag). The analyte (QR) is electrostatically adsorbed on the surface of the MrGO. Finally, the MIP was deposited via in-situ polymerization. The composite was characterized by X-ray diffraction, Fourier transform infrared spectroscopy and Vibrating sample magnetometry. The morphologies and electrochemical properties of different electrodes were characterized by Field emission scanning electron microscopy, Electrochemical impedance spectroscopy and differential pulse voltammetry. Under optimal conditions, the modified electrode has a linear response in the 20 nM to 250 μM QR concentration range. The limit of detection is 13 nM (at an S/N ratio of 3). The electrode is selective, stable, regenerable and reliable. It was applied to the determination of QR in spiked pharmaceutical samples and gave satisfactory results.

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Graphical abstract Schematic presentation of a method for sensing quercetin. It is based on the use of screen printed electrode modified with magnetized reduced graphene oxide and a molecularly imprinted polymer.