Determination Of NADH Research Articles

Photoelectrocatalytic oxidation of NADH in a flow injection analysis system using a poly-hematoxylin modified glassy carbon electrode

A stable electroactive thin film of poly-hematoxylin (poly-HT) was successfully prepared on a glassy carbon electrode (GCE) surface by recording successive cyclic voltammograms of 0.3 mM HT, in a phosphate buffer solution (pH 7.0) containing 0.1 M NaNO 3, in the potential range of −0.5 to +2.0 V vs . Ag/AgCl. The deposition of HT on GCE surface can be explained through the electropolymerization process. This poly-HT modified electrode exhibited a good electrocatalytic activity towards the NADH oxidation in a phosphate buffer solution (pH 7.0), and led to a significant decrease in the overpotential by more than 320 mV compared with the bare GCE. In order to perform the photoelectrocatalytic determination of NADH in a flow injection analysis (FIA) system, a home-made flow electrochemical cell with a suitable transparent window for irradiation of the electrode surface was constructed. Flow rate of carrier solution, transmission tubing length, injection volume and applied potential for the amperometric and photoamperometric FIA studies were optimized as 1.3 mL min −1, 10 cm, 100 μL and +300 mV vs . Ag/AgCl, respectively. The currents obtained from amperometric and photoamperometric measurements in FIA system at optimum conditions were linearly dependent on the NADH concentration and linear calibration curves were obtained in the range of 1.0 × 10 −7–1.5 × 10 −4 M and in the range of 1.0 × 10 −7–2.5 × 10 −4 M NADH, respectively. The relative standard deviation (RSD) of six replicate injections of 6.0 × 10 −5 M NADH was calculated as 2.2% and 4.3% for the amperometric and the photoamperometric method, respectively. The limit of detection was found to be 3.0 × 10 −8 M for the photoamperometric determination of NADH.

Carbon Nanotubes‐Ionic Liquid and Chloropromazine Modified Electrode for Determination of NADH and Fabrication of Ethanol Biosensor

AbstractPotential cycling was used for oxidation of chloropromazine and producing an electroactive redox couples which strongly adsorbed on the electrode surface modified with carbon nanotubes and ionic liquid nanocomposite. The modified electrode shows excellent electrocatalytic activity toward NADH oxidation. The differential pulse voltammetry detection provided high sensitivity, 0.5835 A M−1, low detection limit, 80 nM at concentration range up to 20 μM. An ethanol biosensor was also developed by immobilizing alcohol dehydrogenase enzyme onto nanocomposite. Differential pulse voltammetric detection of ethanol gives linear responses over the concentration range 40 μM–1.5 mM with detection limit 5 μM and sensitivity 1.97 μA mM−1.

Electrocatalytic oxidation of the reduced nicotinamide adenine dinucleotide at carbon ionic liquid electrode modified with polythionine/multi-walled carbon nanotubes composite

A carbon ionic liquid electrode (CILE) was modified with a polythionine (PTh)/multi-walled carbon nanotubes (MWCNTs) composite and used for the detection of reduced nicotinamide adenine dinucleotide (NADH). The electrode was prepared by electrochemical polymerization of thionine on the MWCNTs in neutral medium. Cyclic voltammetry indicated that the electrode was capable of mediating the oxidation of NADH at an overpotential as low as 0.03 V. Amperometric experiments showed that a sensitive and stable response towards NADH is obtained within 5 s. The linear range for the determination of NADH is from 0.8 μmol L−1 to 422 μmol L−1, with a detection limit of 0.26 μmol L−1 (S/N = 3). The wide linear range, lower detection limit and faster response towards NADH suggests that the new method potentially is useful for developing NAD+-dependent enzyme-based biosensors.

Preparation and electrochemical application of rutin biosensor for differential pulse voltammetric determination of NADH in the presence of acetaminophen

The electrocatalytic behavior of reduced nicotinamide adenine dinucleotide (NADH) was studied at the surface of a rutin biosensor, using various electrochemical methods. According to the results, the rutin biosensor had a strongly electrocatalytic effect on the oxidation of NADH with the overpotential being decreased by about 450 mV as compared to the process at a bare glassy carbon electrode, GCE. This value is significantly greater than the value of 220 mV that was reported for rutin embedded in a lipid-cast film. The kinetic parameters of the electron transfer coefficient, ?, and the heterogeneous charge transfer rate constant, kh, for the electrocatalytic oxidation of NADH at the rutin biosensor were estimated. Furthermore, the linear dynamic range; sensitivity and limit of detection for NADH were evaluated using the differential pulse voltammetry method. The advantages of this biosensor for the determination of NADH are excellent catalytic activity and reproducibility, good detection limit and high exchange current density. The rutin biosensor could separate the oxidation peak potentials of NADH and acetaminophen present in the same solution while at a bare GCE, the peak potentials were indistinguishable.

Electrochemical determination of NADH and ethanol based on ionic liquid-functionalized graphene

It is firstly reported that low-potential NADH detection and biosensing for ethanol are achieved at an ionic liquid-functionalized graphene (IL-graphene) modified electrode. A substantial decrease (440 mV) in the overvoltage of the NADH oxidation was observed using IL-graphene/chitosan coating, with oxidation starting at ca. 0 V (vs. Ag|AgCl). And the NADH amperometric response at such a modified electrode is more stable (95.4% and 90% of the initial activity remaining after 10 min and 30 min at 1 mM NADH solution) than that at bare electrode (68% and 46%). Furthermore, the IL-graphene/chitosan-modified electrode exhibited a good linearity from 0.25 to 2 mM and high sensitivity of 37.43 μA mM −1 cm −2. The ability of IL-graphene to promote the electron transfer between NADH and the electrode exhibited a novel and promising biocompatible platform for development of dehydrogenase-based amperometric biosensors. With alcohol dehydrogenase (ADH) as a model, the ADH/IL-graphene/chitosan-modified electrode was constructed through a simple casting method. The resulting biosensor showed rapid and highly sensitive amperometric response to ethanol with a low detection limit (5 μM). Moreover, the proposed biosensor has been used to determine ethanol in real samples and the results were in good agreement with those certified by the supplier.

Electrocatalytic activity of 6,7-dihydroxy-3-methyl-9-thia-4,4a-diazafluoren-2-one/multi-wall carbon nanotubes immobilized on carbon paste electrode for NADH oxidation: Application to the trace determination of NADH

Abstract A 6,7-dihydroxy-3-methyl-9-thia-4,4a-diazafluoren-2-one/multi-wall carbon nanotubes (DDF/MWCNT) film-modified carbon paste electrode (CPE) has been fabricated. The electrochemical oxidation of the behavior of reduced nicotinamide adenine dinucleotide (NADH) has been studied at DDF/MWCNT film-modified CPE by electrochemical methods. The DDF/MWCNT film-modified CPE showed a pair of well-defined, quasi-reversible cyclic voltammogram (CV) which corresponds to the transformation of catechol to o-benzoquinone redox couple. With this modified electrode the oxidation potential of the NADH was shifted about 0.333 V toward a less positive value, presenting a peak current much higher than those measured on an unmodified CPE. Detailed analysis of cyclic voltammograms and chronoamperogram gave fundamental electrochemical parameters including the electroactive surface coverage ( Г ), the transfer coefficient ( α ) and the catalytic rate constant ( k ′). Under the selected conditions, two linear calibration curves for NADH were obtained in the concentration ranges of 1–10 nM and 10–80 nM with the detection limit of 0.7 nM. This modified electrode was quite effective to detect the trace amounts of NADH in the presence of the ascorbic acid (AA) or uric acid (UA).

Poly(brilliant cresyl blue)-carbonnanotube modified electrodes for determination of NADH and fabrication of ethanol dehydrogenase-based biosensor

A single walled-carbon nanotube (SWNT) modified with poly brilliant cresyl blue (PBCB) glassy carbon electrode has been fabricated by a simple, method in order to facilitate electrocatalytic detection of NADH. At this chemically modified electrode, NADH was determined in neutral phosphate buffer solution at 0V (vs. SCE). The amperometric detection provided a wide linear current vs. concentration range (3.0–104.2μM), a fast response time (within 5s), high sensitivity [9.89nA (μM)−1] and a low detection limit (1.0μM, S/N=3). No interference was observed with a 100-fold excess of dopamine or uric acid. An ethanol biosensor also was developed using the nanocomposite modified electrode, by immobilizing ethanol dehydrogenase with carrageenan. In this case a linear ethanol concentration response was achieved in the range from 0.4 to 2.4mM and the detection limit was estimated to be 0.1mM (S/N=3). The analytical performance achieved with the of the PBCB/SWNT nanocomposite electrode is expected to the development of novel biosensors, biofuel cells, and other bioelectrochemical devices.

Amperometric Sensor for Detection of the Reduced Form of Nicotinamide Adenine Dinucleotide Using a Poly(pyronin B) Film Modified Electrode

AbstractAn electrochemical method for the preparation of poly(pyronin B) film was proposed in this paper. A poly(pyronin B) (poly(PyB)) film modified glassy carbon electrode (GCE) has been fabricated via an electrochemical oxidation procedure and applied to the electrocatalytic oxidation of reduced form of nicotinamide adenine dinucleotide (NADH). The poly(PyB) film modified electrode surface has been characterized by atomic force microscope (AFM), scanning electron microscope (SEM), electrochemical impedance spectroscopy (EIS), UV‐visible absorption spectrophotometry (UV‐vis) and cyclic voltammetry (CV). These studies have been used to investigate the poly(PyB) film, which demonstrates the formation of the polymer film and the excellent electroactivity of poly(PyB) in neutral and even in alkaline media. Due to its potent catalytic effects towards the electrooxidation of NADH at lower potential (0.0 V), poly(PyB) film modified electrode can be used for the selective determination of NADH in real samples because of dopamine, ascorbic acid and uric acid oxidation can be avoided at this potential. The catalytic peak currents are linearly dependent on the concentrations of NADH in the range of 1.0×10−6 to 5.0×10−4 mol/L with correlation coefficients of 0.999. The detection limits for NADH is 0.5×10−6 mol/L. Poly(PyB) modified electrode also shows good stability and reproducibility due to the irreversible attachment of polymer film at GCE surface.

Dopamine sensitized nanoporous TiO2 film on electrodes: Photoelectrochemical sensing of NADH under visible irradiation

Dopamine-coordinated photoactive TiO2 nanoporous films with a wide excitation range of light in the visible region (up to 580nm) were prepared and used for sensitive detection of NADH. Colloidal TiO2 was firstly covered on an indium–tin oxide (ITO) electrode surface and sintered at 450°C to form a nanoporous TiO2 film, then the electrode was dipped in a dopamine solution to form a dopamine–TiO2 charge transfer complex via coordinating dopamine with undercoordinated titanium atoms on the electrode surface. This charge transfer complex provided an anodic photocurrent under visible light and the photocurrent could be largely enhanced by NADH. The photocurrent enhancement might be due to the electron transfer between NADH and the holes localized on dopamine. A new photoelectrochemical methodology for sensitive detection of NADH at a relatively low potential was developed. The detection limit of NADH was 1.4×10−7M, and the detection range could extend up to 1.2×10−4M. The dopamine–TiO2 modified electrode exhibits its major advantages such as effective electronic transducer, fast response and easy fabrication for photoelectrochemical determination of NADH. This strategy largely reduces the destructive effect of UV light and the photogenerated holes of illuminated TiO2 to biomolecules and opens a new avenue for the applications of TiO2 in photoelectrochemical biosensing.

Epilepsy and respiratory chain defects in children with mitochondrial encephalopathies

Objective: The purpose of this study was to determine the relationship between epilepsy and respiratory chain defects in children with mitochondrial encephalopathies (ME). Study Design: We conducted a retrospective review of the medical records of children referred for evaluation of an ME. Only patients assigned a definite diagnosis of ME using modified Walker criteria and with a respiratory chain defect were included. Clinical data pertaining to the ME and epilepsy type were collected. Mitochondria were isolated by subcellular fractionation from a vastus lateralis muscle biopsy and studies were performed using polarographic and spectroscopic techniques for the quantitative determination of NADH and cytochrome components of the respiratory chain. Results: A total of 38 children with ME were identified. Seizures were present in 61%. Sixteen of 23 children with epilepsy (70%) had refractory epilepsy associated with a progressive encephalopathy. Children with epilepsy had a significantly higher incidence of complex I defects than children without epilepsy (p<0.01). Complex III and IV defects were significantly higher in patients without epilepsy (p<0.01 and p<0.05, respectively) than in those with epilepsy. Conclusions: Epilepsy is an important component of ME. The higher incidence of complex I defects in patients with epilepsy suggests a possible relationship between mitochondrial oxidative stress dysfunction and epileptogenic process.

Electrocatalytic detection of NADH and ethanol at glassy carbon electrode modified with electropolymerized films from methylene green

The oxidation of NADH on electropolymerizing methylene green (MG)-modified glassy carbon electrode (GCE) is described. The modified electrode shows an excellent electrocatalytic activity toward NADH oxidation, reducing its overpotential by about 650 mV and exhibits a wide linear range of 5.6–420 μM NADH with the detection limit of 3.8 μM. The electrode displays a good reproducibility and stability and the coexisting species does not affect the determination of NADH. The application in the amperometric biosensing of ethanol using alcohol dehydrogenase enzyme (ADH) also has been demonstrated with this electrode. MG-modified GCE can not only be used to detect NADH in biochemical reaction, but also can be used as the potential matrix of the construction of dehydrogenases biosensor.

A simple route to incorporate redox mediator into carbon nanotubes/Nafion composite film and its application to determine NADH at low potential

Through a new and simple ion-exchange route, two-electron redox mediator thionine has been deliberately incorporated into the carbon nanotubes (CNTs)/Nafion composite film due to the fact that there is strong interaction between any of two among the three materials (ion-exchange process between thionine and Nafion, strong adsorption of thionine by CNTs, and wrapping and solubilizing of CNTs with Nafion). The good homogenization of electron conductor CNTs in the integrated films provides the possibility of three-dimensional electron conductive network. The resulting integrated films exhibited high and stable electrocatalytic activity toward NADH oxidation with the significant decrease of high overpotential, which responds more sensitively more than those modified by thioine or CNTs alone. Such high electrocatalytic activity facilitated the low potential determination of NADH (as low as −0.1 V), which eliminated the interferences from other easily oxidizable species. In a word, the immobilization approach is very simple, timesaving and effective, which could be extended to the immobilization of other cationic redox mediators into the CNTs/Nafion composite film. And these features may offer potential promise for the design of amperometric biosensors.

Room-temperature ionic liquids/multi-walled carbon nanotubes/chitosan composite electrode for electrochemical analysis of NADH

Abstract An electrochemical sensing platform was developed based on the integration of room-temperature ionic liquids (1-butyl-3-methylimidazolium tetrafluoroborate, BMIM·BF4) and multi-walled carbon nanotubes (MWNTs) with polymeric matrix (chitosan, CHIT). The resulting composite were investigated and characterized by FTIR, TEM, SEM, EDS and electrochemical methods. The BMIM·BF4/MWNTs/CHIT have good dispersibility in aqueous solution and can form a relative uniform film with unique structure. Electrochemical studies suggested that the BMIM·BF4/MWNTs/CHIT composite system provided a synergistic augmentation on the voltammetric and amperometric behaviors of electrochemical oxidation of NADH, which indicated by the decrease of the peak potential of NADH oxidation and the improvement of amperometric response. Additionally, the BMIM·BF4/MWNTs/CHIT/GC electrode shows good analytical performance such as low detection limit (0.06 μM), good regeneration and anti-fouling properties for determination of NADH. This nanomaterials-based composite may be used as electrochemical transducers and have potential application for designing a variety of NAD+-dependent electrochemical biosensors.

Cationic dyes immobilized on cellulose acetate surface modified with titanium dioxide: factorial design and an application as sensor for NADH

The electrochemical properties of meldola blue and toluidine blue cationic dyes immobilized on cellulose acetate surface modified with titanium dioxide were investigated by cyclic voltammetry. The materials synthesized were employed as carbon paste electrodes. The redox mediator properties of the meldola blue and toluidine blue chemically modified electrodes were optimized using a factorial design, consisting of two levels and four factors with two pseudo-central points (n= 20 experiments). The factorial analysis was carried out by searching for better reversibility of the redox process, such as the lowest separation between anodic and cathodic potential peaks and a current ratio near unity. The factors that presented significant effects on the overall optimization of the system to achieve the best conditions of the reversibility of electron transfer were the main factors scan rate and type of electrode (meldola blue or toluidine blue), besides the interaction factors KCl concentration × type of electrode (B×D) and the pH × [KCl] concentration × scan rate (A×B×C) interaction. The best electrochemical reversibility conditions obtained were: using the CA-TiO2-MB electrode, 1.0 mol L-1 KCl as supporting electrolyte, at scan rate of 10.0 mV s-1. Afterwards, the CA-TiO2-MB modified electrode was tested as an amperometric sensor for the determination of NADH, with a detection limit of 0.1 µmol L-1.

Mediatorless catalytic oxidation of NADH at a disposable electrochemical sensor

We report here a simple, selective and sensitive method for the determination of NADH in neutral aqueous solution by using an electrochemically preanodized screen printed carbon electrode (SPCE *) without the addition of any redox mediator. The preanodization procedure makes the SPCE more electroactive towards NADH oxidation with a decrease of ∼300 mV in the overpotential without electrode fouling. It is proposed that surface reorientation to generate more edge plane sites during the preanodization procedure, as confirmed by a distinctive Raman band at ∼1360 cm −1, is the main cause for the facilitated electron transfer for the oxidation of NADH. Presence of large excess of ascorbic acid does not interfere the detection of NADH and the SPCE * shows individual voltammetric peaks for ascorbic acid and NADH. Under optimized conditions, the obtained calibration plot shows a linear range up to 100 μM with a detection limit (S/N = 3) of 157 nM by flow injection analysis.

Synergistic effect of a catechin-immobilized poly(3,4-ethylenedioxythiophene)-modified electrode on electrocatalysis of NADH in the presence of ascorbic acid and uric acid

Catechin is a polyphenolic flavonoid that can be isolated from a variety of natural sources, including tea leaves, grape seeds, and the wood and bark of trees such as acacia and mahogany. In our experiments, catechin was immobilized on PEDOT/GC (poly(3,4-ethylenedioxythiophene)/glassy carbon)-modified electrodes and used as a mediator for NADH (nicotinamide adenine dinucleotide) oxidation. The effect of the PEDOT thickness on the surface coverage of the catechin molecules was studied using cyclic voltammetry. The electrochemical properties and the effect of pH on the redox properties of the immobilized catechin molecules were studied by cyclic voltammetry in phosphate solution. The electrocatalytic oxidation of NADH at different electrode surfaces such as the bare GC-, the PEDOT/GC-, the catechin/GC- and the catechin/PEDOT/GC-modified electrodes was explored in phosphate solution at pH 7. In the catechin/PEDOT/GC-modified electrode, the PEDOT film plays an important role in resolving the oxidation potentials of ascorbic acid and NADH into two peaks that occur at the same potential for the catechin/GC-modified electrode surface. The heterogeneous electron transfer rate constant for NADH oxidation at the catechin/PEDOT/GC-modified electrode was determined using the rotating disk electrode technique and found to be 9.88 × 10 3 M −1 s −1. The amperometric determination of NADH at the catechin/PEDOT/GC electrode was tested. The sensitivity of the electrode was 19 nA/μM.

Fabrication of carbon nanotubes/poly(1,2-diaminobenzene) nanoporous composite via multipulse chronoamperometric electropolymerization process and its electrocatalytic property toward oxidation of NADH

A novel method was proposed for fabrication of a carbon nanotubes/poly(1,2-diaminobenzene) nanoporous composite based electrode. The poly(1,2-diaminobenzene) was deposited onto the surface of a glassy carbon electrode (GCE) modified with multi-wall carbon nanotubes (MWNTs) via multipulse chronoamperometric electropolymerization (MCE) process. Compared with the composite prepared by conventional electropolymerization (CE), the electronic and ionic transport capacity of the MCE-based composite were significantly improved due to its unique nanoporous structure. The surface of the composite-modified GCE was characterized with scanning electron microscopy (SEM) and cyclic voltammetry (CV). The nanoporous MCE-based electrode was applied to determination of NADH at a much low potential of 70 mV, and a linear range from 2.0 μM to 4.0 mM was observed with fast response (within 5 s) and a lower detection limit of 0.5 μM (based on S/N = 3). In comparison, a narrow linear range from 5.0 μM to 2.0 mM, slower response (up to 15 s) and a higher detection limit of 3.0 μM (based on S/N = 3) was obtained with the electrode prepared by CE. The wider linear range, lower detection limit and fast response of the MCE-based electrode implies that the new method proposed can provide more excellent platforms for sensitive electrochemical sensing and biosensing.

Chemical adsorption of phenothiazine dyes onto carbon nanotubes: Toward the low potential detection of NADH

The cyclic voltammetric responses for phenothiazine dyes, adsorbed onto CNT have been assessed as a means of promoting the low potential, sensitive and stable determination of NADH. The analytical signal of the toluidine blue modified carbon nanotubes (TB-CNT) has been evaluated and compared with those of the bare carbon nanotubes and toluidine blue coated basal plane graphite electrodes; significant improvements in both the sensitivity and stability are demonstrated when using amperometic detection. The bulk modification of the CNT has allowed for the development of an inexpensive and facile electrode design, in which the CNT are packed into a small cavity. The electrode was found to be stable and gave greatly improved signals over its toluidine blue coated graphite powder counterpart.

Preparation and Electrochemical Study of Fisetin Modified Glassy Carbon Electrode. Application to the Determination of NADH and Ascorbic Acid

AbstractA new modified electrode, FMGCE, was prepared by electrodeposition of fisetin (F) at the surface of a preactivated glassy carbon electrode. Cyclic voltammetry was used to investigate the electrochemical properties of this electrode. The charge transfer rate constant, ks, and transfer coefficient, αs, for electron transfer between electrode substrate and surface deposited F were calculated as 16.34 s−1 and 0.54, respectively. The electrode ability towards the electrocatalytic oxidation of dihydronicotinamide adenine dinucleotide (NADH) and ascorbic acid (AA) was also studied using cyclic voltammetry and chronoamperometry as diagnostic techniques. The catalytic currents of NADH and AA were used for determination of heterogeneous rate constant, kh, of these substrates oxidation at the surface of modified electrode. The diffusion coefficients of both substrates were also estimated using chronoamperometric results. Finally, FMGCE was used as voltammetric and amperometric sensors for determination of NADH and AA in quiet and moving solutions respectively. The calculated limit of detection of NADH and AA by voltammetry were 0.06 and 0.05 mM, respectively. While, these values decrease to 2.4 and 1.8 μM, respectively for an amperometric procedure. The latter method was used successfully for quantification of AA in some real samples.

Exploring the electrocatalytic sites of carbon nanotubes for NADH detection: an edge plane pyrolytic graphite electrode study

The electrocatalytic properties of multi-walled carbon nanotube modified electrodes toward the oxidation of NADH are critically evaluated. Carbon nanotube modified electrodes are examined and compared with boron-doped diamond and glassy carbon electrodes, and most importantly, edge plane and basal pyrolytic graphite electrodes. It is found that CNT modified electrodes are no more reactive than edge plane pyrolytic graphite electrodes with the comparison with edge plane and basal plane pyrolytic graphite electrodes allowing the electroactive sites for the electrochemical oxidation of NADH to be unambiguously determined as due to edge plane sites. Using these highly reactive edge plane sites, edge plane pyrolytic graphite electrodes are examined with cyclic voltammetry and amperometry for the electroanalytical determination of NADH. It is demonstrated that a detection limit of 5 microM is possible with cyclic voltammetry or 0.3 microM using amperometry suggesting that edge plane pyrolytic graphite electrodes can conveniently replace carbon nanotube modified glassy carbon electrodes for biosensing applications with the relative advantages of reactivity, cost and simplicity of preparation. We advocate the routine use of edge plane and basal plane pyrolytic graphite electrodes in studies utilising carbon nanotubes particularly if 'electrocatalytic' properties are claimed for the latter.