An amperometric uric acid biosensor based on modified Ir-C electrode

The level of uric acid (UA) has a high relationship with gout, hyperuricemia and Lesch-Nyan syndrome. The determination of UA is an important indicator for clinics and diagnoses of kidney failure. An amperometric UA biosensor based on an Ir-modified carbon (Ir-C) working electrode with immobilizing uricase (EC 1.7.3.3) was developed by thick film screen printing technique. This is the first time to report the utilization of an uricase/Ir-C electrode for the determination of UA by using chronoamperometric (CA) method. The high selectivity of UA biosensor was achieved due to the reduction of H(2)O(2) oxidation potential based on Ir-C electrode. Using uricase/Ir-C as the sensing electrode, the interference from the electroactive biological species, such as ascorbic acid (AA) and UA (might be directly oxidized on the sensing electrode) was slight at the sensing potential of 0.25 V (versus Ag/AgCl). UA was detected amperometrically based on uricase/Ir-C electrode with a sensitivity of 16.60 microAmM(-1) over the concentration range of 0.1-0.8 mMUA, which was within the normal range in blood. The detection limit of UA biosensor was 0.01 mM (S/N=6.18) in pH 7 phosphate buffer solution (PBS) at 37 degrees C. The effects of pH, temperature, and enzymatic loading on the sensing characteristics of the UA biosensor were also investigated in this study.     

A reusable amperometric biosensor based on a novel silver-epoxy electrode for immunoglobulin detection

A renewable immunosensor consisting of an `epoxygraphite' biocomposite containing silver and tetracyanoquinodimethane (TCNQ) is described. These compounds enhance conductivity allowing the use of a smaller potential (0.28 v) which, in turn, enhances selectivity. This sensor, which may be renewed by simple polishing of its surface, was employed to detect human IgG using peroxidase-coupled anti-human IgG.     

An amperometric pyruvate biosensor based on pyruvate oxidase nanoparticles immobilized onto pencil graphite electrode

This present study was aimed to fabricate a sensitive and improved amperometric biosensor by the nanoparticles of pyruvate oxidase, which were prepared and immobilized covalently onto pencil graphite electrode. The biosensor showed ideal working within 5 s under defined conditions of pH 6.0 and incubation temperature of 30 °C at an applied voltage of -0.1 V. Under standard assay conditions, a linear response was obtained between pyruvate concentration ranging from 0.001 to 6000 μM and current (μA). A lower detection limit (0.58 μM) and an excellent correlation coefficient (R² = 0.999) with standard spectrophotometric assay was obtained for the present biosensor. Within and between batches of coefficients of variation were calculated and found to be 3.61 % and 3.33 %, respectively. The biosensor was put to continual use for over 210 days. The biosensor was employed for the measurement of pyruvate level in sera of normal healthy individuals and persons suffering from heart disease.     

Hydrogen peroxide sensitive amperometric biosensor based on horseradish peroxidase entrapped in a polypyrrole electrode

The enzyme horseradish peroxidase (HRP) has been entrapped in situ by electropolymerization of pyrrole onto a platinum electrode. The latter was previously coated by a polypyrrole layer for better adhesion of the biocatalyst film and in order to avoid the enzyme folding onto the Pt electrode. The biosensor allowed the determination of hydrogen peroxide in the concentration range comprised between 4.9 x 10(-7) and 6.3 x 10(-4) M. The biosensor retained more than 90% of its original activity after 35 days of use.     

A selective novel non-enzyme glucose amperometric biosensor based on lectin-sugar binding on thionine modified electrode

A novel non-enzyme glucose amperometric biosensor was fabricated based on biospecific binding affinity of concanavalin A (Con A) for D-glucose on thionine (TH) modified electrode. TH can be covalently immobilized on potentiostatically activated glassy carbon electrode through Schiff-base reaction. Subsequently, the surface-adherent polydopamine film formed by self-polymerization of dopamine attached to TH and afforded binding sites for the subsequent immobilization of Con A molecules via Michael addition and/or Schiff-base reaction with high stability. Thus, a sensing platform for specific detection towards D-glucose was established. The binding of Con A towards D-glucose can be monitored through the decrease of the electrode response of the TH moiety. Due to the high affinity of Con A for D-glucose and high stability of the resulting sensing platform, the fabricated biosensor exhibited high selectivity, good sensitivity, and wide linear range from 1.0×10(-6) to 1.0×10(-4) M with a low detection limit of 7.5×10(-7) M towards D-glucose.     

Internal supply of coenzyme to an amperometric glucose biosensor based on a chemically modified electrode

A biosensor for glucose using glucose dehydrogenase immobilized on a chemically modified graphite electrode was supplied with coenzyme, nicotinamide adenine dinucleotide (NAD+), through pores in the material. A graphite rod was hollowed out, leaving 0.3 mm at the end contacting the solution, filled with 10 mM NAD+ and pressurized. The response factor was 40% of that obtained when 2 mM NAD+ was mixed with the sample solution in a flow system. The coenzyme consumption was 11 microliters h-1 representing a 500-fold saving compared to supply through the bulk solution. The biosensor had a linear calibration curve from the detection limit, 1 microM, to 2 mM glucose and a repeatability of 0.3%. The graphite electrode was modified by adsorption of a bis-(benzophenoxazinyl)-terephthaloyl derivative in order to be able to oxidize NADH at 0 mV versus Ag/AgCl, 0.1 M KCl.     

Fabrication of polyphenol biosensor based on laccase immobilized on copper nanoparticles/chitosan/multiwalled carbon nanotubes/polyaniline-modified gold electrode

A high-performance amperometric polyphenol biosensor was developed, based on covalent immobilization of Ganoderma sp. laccase onto copper nanoparticles (CuNP's)/chitosan (CHIT)/carboxylated multiwalled carbon nanotube (cMWCNT)/polyaniline (PANI)-modified gold (Au) electrode. The CuNP's and cMWCNT had a synergistic electrocatalytic effect in the matrix of CHIT. The biosensor showed optimum response at pH 6.0 (0.1 M acetate buffer) and 35 °C, when operated at 50 mV s⁻¹. The biosensor exhibited excellent sensitivity (the detection limit was down to 0.156 μM for guaiacol), fast response time (less than 4 s) and wide linear range (from 1 to 500 μM). Analytical recovery of added guaiacol was 96.40-98.46%. Within batch and between batch coefficients of variation were <2.6% and <5.3%, respectively. The enzyme electrode was used 300 times over a period of 7 months, when stored at 4 °C.     

Disposable biosensor based on enzyme immobilized on Au-chitosan-modified indium tin oxide electrode with flow injection amperometric analysis

Indium tin oxide (ITO) electrode is used to fabricate a novel disposable biosensor combined with flow injection analysis for the rapid determination of H2O2. The biosensor is prepared by entrapping horseradish peroxidase (HRP) enzyme in colloidal gold nanoparticle-modified chitosan membrane (Au-chitosan) to modify the ITO electrode. The biosensor is characterized by scanning electron microscope, atomic force microscope, and electrochemical methods. Parameters affecting the performance of the biosensor, including concentrations of o-phenylenediamine (OPD) and pH of substrate solution, were optimized. Under the optimal experimental conditions, H2O2 could be determined in the linear calibration range from 0.01 to 0.5 mM with a correlation coefficient of 0.997 (n=8). The amperometric response of the biosensor did not show an obvious decrease after the substrates were injected continuously 34 times into the flow cell. The prepared biosensor not only is economic and disposable, due to the low-cost ITO film electrode obtained from industrial mass production, but also is capable with good detection precision, acceptable accuracy, and storage stability for the fabrication in batch.     

Bienzymatic amperometric biosensor for choline based on mediator thionine in situ electropolymerized within a carbon paste electrode

An amperometric enzyme biosensor for the determination of choline utilizing two enzymes, choline oxidase (CHOD) and horseradish peroxidase (HRP), is described. The biosensor consisted of CHOD cross-linked onto a HRP-immobilized carbon paste electrode. The biosensor was prepared by in situ electropolymerization of poly(thionine) within a carbon paste containing the enzyme HRP and thionine monomer and then CHOD was immobilized by using chitosan film through cross-linking with glutaraldehyde. The in situ electrogenerated poly(thionine) displays excellent electron transform efficiency between the enzyme HRP and the electrode surface, and the polymer enables improvement in enzyme immobilization within the paste. Several parameters such as the amount of thionine and enzyme, the applied potential, the pH, etc. have been studied. Amperometric detection of choline was realized at an applied potential of -0.2V vs saturated calomel electrode in 1/15M phosphate buffer solution (pH 7.4) with a linear response range between 5.0 x 10(-6) and 6.0 x 10(-4)M choline and a response time of 15s. When applied to the analysis of phosphatidylcholine in serum samples, a 0.997 correlation was obtained between the biosensor results and those obtained by a hospital method.     

An amperometric glucose biosensor based on poly(o-aminophenol) and Prussian blue films at platinum electrode

Prussian blue (PB), as a good catalyst for the reduction of hydrogen peroxide, has been combined with nonconducting poly(o-aminophenol) (POAP) film to assemble glucose biosensor. Compared with PB-modified enzymatic biosensor, the biosensor based on glucose oxidase immobilized in POAP film at PB-modified electrode shows much improved stability (78% remains after 30 days) in neutral medium. Additionally, the biosensor, at an applied potential of 0.0 V, exhibits other good characteristics, such as relative low detection limit (0.01 mM), short response time (within 5s), large current density (0.28 mA/cm2), high sensitivity (24 mAM(-1)cm(-2)), and good antiinterferent ability. The apparent activation energy of enzyme-catalyzed reaction and apparent Michaelis-Menten constant are 34.2 KJmol(-1) and 10.5 mM, respectively. In addition, effects of temperature, applied potential used in the determination, pH value of the detection solution, and electroactive interferents on the amperometric response of the sensor were investigated and are discussed.     

A mediator-free amperometric hydrogen peroxide biosensor based on HRP immobilized on a nano-Au/poly 2,6-pyridinediamine-coated electrode

A mediator-free amperometric hydrogen peroxide biosensor was prepared by immobilizing horseradish peroxidase (HRP) enzyme on colloidal Au modified platinum (Pt) wire electrode, which was modified by poly 2,6-pyridinediamine (pPA). The modified process was characterized by electrochemical impedance spectroscopy (EIS), and the electrochemical characteristics of the biosensor were studied by cyclic voltammetry, linear sweep voltammetry and chronoamperometry. The biosensor displayed an excellent electrocatalytical response to reduction of H₂O₂ without the aid of an electron mediator, the linear range was 4.2 × 10⁻⁷–1.5 × 10⁻³ mol/L (r = 0.9977), with a detection limit of 1.4 × 10⁻⁷ mol/L. Moreover, the performance and factors influencing the resulted biosensor were studied in detail. The studied biosensor exhibited permselectivity, good stability and good fabrication reproducibility.     

Cholesterol amperometric biosensor based on cytochrome P450scc

A screen-printed enzyme electrode based on flavocytochrome P450scc (RfP450scc) for amperometric determination of cholesterol has been developed. A one-step method for RfP450scc immobilization in the presence of glutaraldehyde or by entrapment of enzyme within a hydrogel of agarose is discussed. The sensitivity of the biosensor based on immobilization procedures of flavocytochrome P450scc by glutaric aldehyde is 13.8 nA microM(-1) and the detection limit is 300 microM with a coefficient of linearity 0.98 for cholesterol in the presence of sodium cholate as detergent. The detection limits and the sensitivity of the agarose-based electrode are 155 microM and 6.9 nA microM(-1) with a linearity coefficient of 0.99. For both types of electrodes, the amperometric response to cholesterol in the presence of detergent was rather quick (1.5-2 min).     

Development of an amperometric sulfite biosensor based on SO(x)/PBNPs/PPY modified ITO electrode

A sulfite oxidase (SO(x)) (EC 1.8.3.1) purified from Syzygium cumini leaves was immobilized onto prussian blue nanoparticles/polypyrrole composite (PBNPs/PPY) electrodeposited onto the surface of indium tin oxide (ITO) electrode. An amperometric sulfite biosensor was fabricated using SO(x)/PBNPs/PPY/ITO electrode as working electrode, Ag/AgCl as standard and Pt wire as auxiliary electrode connected through a potentiostat. The working electrode was characterized by Fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) before and after immobilization of SO(x). The biosensor showed optimum response within 2s, when operated at 20mVs(-1) in 0.1M Tris-HCl buffer, pH 8.5 and at 35°C. Linear range and minimum detection limit were 0.5-1000μM and 0.12μM (S/N=3) respectively. There was good correlation (r=0.99) between red wine samples sulfite value by standard DTNB method and the present method. The sensor was evaluated with 97% recovery of added sulfite in red wine samples and 2.2% and 4.3% within and between batch coefficients of variation respectively. The sensor was employed for determination of sulfite level in red and white wine samples. The enzyme electrode was used 200 times over a period of 3 months when stored at 4°C.     

An amperometric biosensor based on laccase immobilized onto MnO2NPs/cMWCNT/PANI modified Au electrode

A method is described for construction of an amperometric biosensor for detection of phenolic compounds based on covalent immobilization of laccase (Lac) onto manganese dioxide nanoparticles (MnO(2)NPs) decorated carboxylated multiwalled carbon nanotubes (cMWCNTs)/PANI composite electrodeposited onto a gold (Au) electrode through N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxy succinimide (NHS) chemistry. The modified electrode was characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The biosensor showed optimum response at pH 5.5 (0.1M sodium acetate buffer) and 35°C, when operated at 0.3 V vs. Ag/AgCl. Linear range, response time, detection limit were 0.1-10 μM (lower concentration range) and 10-500 μM (higher concentration range), 4s and 0.04 μM, respectively. Biosensor measured total phenolic content in tea leaves extract. The enzyme electrode was used 150 times over a period of 5 months.     

Fabrication of an amperometric d-amino acid biosensor based on nickel hexacyanoferrate polypyrrole hybrid film deposited on glassy carbon electrode

A nickel hexacyanoferrate polypyrrole film was synthesized through an electrochemical two-step methodology leading to a very stable and homogenous robust hybrid film. A highly sensitive, specific and rapid amperometric d-amino acid biosensor was constructed by immobilizing d-amino acid oxidase on this film deposited over the surface of a glassy carbon electrode. The modified electrode was characterized by scanning electron microscopy, electrochemical impedance spectroscopy and Fourier transform infrared spectrophotometry. The biosensor showed optimum response within 1 s, when operated at 50 mV s^?1 in 0.01 M Tris HCl buffer, pH 7.0 at 30 °C. The biosensor exhibited excellent sensitivity with a detection limit of 1.5 µM (S/N = 3) for d-amino acids and wider linear range, 20–500 µM. Analytical recovery of added d-alanine (5 and 10 mM) in serum samples was 98.00 and 98.80 %, respectively. Within-batch and between-batch coefficients of variation in serum samples were 1.36 and 2.77 %, respectively. The enzyme electrode was used more than 50 times over 2 months, when stored at 4 °C. The proposed modified electrode exhibited sufficient mechanical and electrochemical stability and high sensitivity compared to earlier electrochemical d-amino acid biosensors. Interference by ascorbic acid and uric acid, the main interfering species in the biological samples, was negligible.     

Detection of pesticides using an amperometric biosensor based on ferophthalocyanine chemically modified carbon paste electrode and immobilized bienzymatic system

A new highly sensitive amperometric method for the detection of organophosphorus compounds has been developed. The method is based on a ferophthalocyanine chemically modified carbon paste electrode coupled with acetylcholinesterase and choline oxidase co-immobilized onto the surface of a dialysis membrane. The activity of cholinesterase is non-competitively inhibited in the presence of pesticides. The highest sensitivity to inhibitors was found for a membrane containing low enzyme loading and this was subsequently used for the construction of an amperometric biosensor for pesticides. Analyses were done using acetylcholine as substrate; choline produced by hydrolysis in the enzymatic layer was oxidized by choline-oxidase and subsequently H(2)O(2) produced was electrochemically detected at +0.35 V vs. Ag/AgCl. The decrease of substrate steady-state current caused by the addition of pesticide was used for evaluation. With this approach, up to 10(-10) M of paraoxon and carbofuran can be detected.     

An amperometric lactate biosensor based on lactate dehydrogenase immobilized onto graphene oxide nanoparticles‐modified pencil graphite electrode

A novel amperometric lactate biosensor was developed based on immobilization of lactate dehydrogenase onto graphene oxide nanoparticles‐decorated pencil graphite electrode. The enzyme electrode was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), and cyclic voltammetry at different stages of its construction. The biosensor showed optimum response within 5 s at pH 7.3 (0.1 M sodium phosphate buffer) and 35°C, when operated at 0.7 V. The biosensor exhibited excellent sensitivity (detection limit as low as 0.1 μM), fast response time (5 s), and wider linear range (5–50 mM). Analytical recovery of added lactic acid in serum was between 95.81–97.87% and within‐batch and between‐batch coefficients of variation were 5.04 and 5.40%, respectively. There was a good correlation between serum lactate values obtained by standard colorimetric method and the present biosensor (r = 0.99). The biosensor measured lactate levels in sera of apparently healthy subjects and persons suffering from lactate acidosis and other biological materials (milk, curd, yogurt, beer, white wine, and red wine). The enzyme electrode lost 25% of its initial activity after 60 days of its regular uses, when stored dry at 4°C.     

A nylon membrane based amperometric biosensor for polyphenol determination

A nylon membrane based amperometric biosensor employing banana fruit polyphenol oxidase (PPO) is presented for polyphenol detection. Nylon membrane was first activated and then coupled with chitosan. PPO was covalently attached to this membrane through glutaraldehyde coupling. The membrane bioconjugate was characterized by scanning electron microscopy (SEM) and Fourier Transform Infrared (FTIR) study and then mounted onto Au electrode using parafilm to construct a working electrode. Once assembled along with Ag/AgCl as reference and Pt as auxiliary electrode, the biosensor gave optimum response within 15 s at pH 7.5 and 30 °C, when polarized at +0.4 V. The response (in mA) was directly proportional to polyphenol concentration in the range 0.2–400 μM. The lower detection limit of the biosensor was 0.2 μM. The biosensor was employed for determination of polyphenols in tea, beverages and water samples. The enzyme electrode showed 25% decrease in initial activity after 150 reuses over 6 months, when stored at 4 °C.     

Development of a commercial amperometric biosensor electrode for the ketone D-3-hydroxybutyrate

Representatives of the common classes of quinoid NADH redox mediator, including Meldola Blue (MB) 3, 4-methyl-1,2-benzoquinone (4-MBQ) 4, 1-methoxy phenazine methosulphate (1-MeO-PMS) 5 and 2,6-dichloroindophenol (DCIP) 6, are shown to inhibit the NAD-dependent enzyme D-3-hydroxybutyrate dehydrogenase (HBDH), severely limiting their utility in the construction of a stable biosensor electrode for the ketone body D-3-hydroxybutyrate (3-OHB). It is proposed that these mediators bind covalently to important thiol groups in the enzyme. This mode of inhibition is overcome through the use of mediators such as 1,10-phenanthroline quinone (1,10-PQ) 7, which avoid 1,4-nucleophilic addition with enzyme amino acid residues such as Cys. As a result, 1,10-PQ 7 was selected for incorporation in a biosensor electrode for 3-OHB. The resulting MediSense Optiumtrade mark beta-Ketone electrode is stable (相似文献   

Construction of a triglyceride amperometric biosensor based on chitosan-ZnO nanocomposite film

A method is described for construction of a novel amperometric triglyceride (TG) biosensor based on covalent co-immobilization of lipase, glycerol kinase (GK) and glycerol-3-phosphate oxidase (GPO) onto chitosan (CHIT) and zinc oxide nanoparticles (ZnONPs) composite film deposited on the surface of Pt electrode. The enzymes-ZnONPs-CHIT composite was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The sensor showed optimum response within 6 s at pH 7.5 and temperature of 35 °C. The sensor measures current due to electrons generated at 0.4 V against Ag/AgCl from H₂O₂, which is produced from triolein by co-immobilized enzymes. A linear relationship was obtained between a wide triolein concentration range (50-650 mg/dl) and current (mA) under optimum conditions. The biosensor showed high sensitivity, low detection limit (20 mg/dl) and good storage stability (half-life of 7 months at 4 °C). The biosensor was unaffected modified by a number of serum substances at their physiological concentrations. The biosensor was evaluated and employed for determination of TG in sera in apparently healthy subjects and persons suffering from hypertriglyceridemia.