Amperometric Xanthine Research Articles

Nanomaterial-Doped Xerogels for Biosensing Measurements of Xanthine in Clinical and Industrial Applications.

First-generation amperometric xanthine (XAN) biosensors, assembled via layer-by-layer methodology and featuring xerogels doped with gold nanoparticles (Au-NPs), were the focus of this study and involved both fundamental exploration of the materials as well as demonstrated usage of the biosensor in both clinical (disease diagnosis) and industrial (meat freshness) applications. Voltammetry and amperometry were used to characterize and optimize the functional layers of the biosensor design including a xerogel with and without embedded xanthine oxidase enzyme (XOx) and an outer, semi-permeable blended polyurethane (PU) layer. Specifically, the porosity/hydrophobicity of xerogels formed from silane precursors and different compositions of PU were examined for their impact on the XAN biosensing mechanism. Doping the xerogel layer with different alkanethiol protected Au-NPs was demonstrated as an effective means for enhancing biosensor performance including improved sensitivity, linear range, and response time, as well as stabilizing XAN sensitivity and discrimination against common interferent species (selectivity) over time-all attributes matching or exceeding most other reported XAN sensors. Part of the study focuses on deconvoluting the amperometric signal generated by the biosensor and determining the contribution from all of the possible electroactive species involved in natural purine metabolism (e.g., uric acid, hypoxanthine) as an important part of designing XAN sensors (schemes amenable to miniaturization, portability, or low production cost). Effective XAN sensors remain relevant as potential tools for both early diagnosis of diseases as well as for industrial food monitoring.

An improved amperometric determination of xanthine with xanthine oxidase nanoparticles for testing of fish meat freshness

The nanoparticles of xanthine oxidase (XODNPs) were prepared by desolvation method and characterized by transmission electron microscopy(TEM) and Fourier transform Infra-red spectroscopy(FTIR). These XODNPs were immobilized directly onto surface of Au electrode via covalent bond. An improved amperometric xanthine biosensor was fabricated using XODNPs modified Au electrode, as working electrode (WE), Ag/AgCl as reference electrode and Pt wire as auxiliary electrode connected through potentiostat.The biosensor showed optimum current at 0.25 V within 5 s, at pH 7.0 and 35 °C.The working range of biosensor was 0.01–1.0 μM with a limit of detection of 0.01 μM.The % recovery of added xanthine (1 and 5 μM) was 94.1 ± 0.2 and 94.8 ± 0.31 respectively. Within and between batch coefficient of variation (CV) were <2% & < 2.5% respectively. A good correlation (R2 = 0.996) was obtained between xanthine contents in various fish meat,as measured by the present biosensor and the standard bienzymic colorimetric method. The biosensor was employed for measuring xanthine level in fish meat at different stages of storage to test its freshness. The XODNPs modified Au electrode was stored dry at 4 °C for 2 months.

Novel electrochemical xanthine biosensor based on chitosan–polypyrrole–gold nanoparticles hybrid bio-nanocomposite platform

The aim of this study was the electrochemical detection of the adenosine-3-phosphate degradation product, xanthine, using a new xanthine biosensor based on a hybrid bio-nanocomposite platform which has been successfully employed in the evaluation of meat freshness. In the design of the amperometric xanthine biosensor, chitosan–polypyrrole–gold nanoparticles fabricated by an in situ chemical synthesis method on a glassy carbon electrode surface was used to enhance electron transfer and to provide good enzyme affinity. Electrochemical studies were carried out by the modified electrode with immobilized xanthine oxidase on it, after which the biosensor was tested to ascertain the optimization parameters. The Biosensor exhibited a very good linear range of 1–200 μM, low detection limit of 0.25 μM, average response time of 8 seconds, and was not prone to significant interference from uric acid, ascorbic acid, glucose, and sodium benzoate. The resulting bio-nanocomposite xanthine biosensor was tested with fish, beef, and chicken real-sample measurements.

Preparation, Characterization and Electrochemical Application of Graphene‐metallic Nanocomposites

AbstractThree different Graphene‐Metallic (Graphene‐Me) nanocomposites – Graphene‐Silver (Graphene‐Ag), Graphene‐Gold (Graphene‐Au) and Graphene‐Platinum (Graphene‐Pt) nanocomposites – were prepared and characterized. The electrochemical performances of these nanocomposites were tested by incorporating them with glassy carbon paste electrode (GCPE) and used them in biofuel cells (BFC) and as amperometric xanthine biosensor transducers. Present work contains the first application of Graphene‐Au and Graphene‐Ag nanocomposite in BFCs and also first application of these Graphene‐Me nanocomposites in xanthine biosensors. Considering BFC, power and current densities were calculated as 2.03 µW cm−2 and 167.46 µA cm−2 for the plain BFC, 3.39 µW cm−2 and 182.53 µA cm−2 for Graphene‐Ag, 4.43 µW cm−2 and 230.15 µA cm−2 for Grapehene‐Au and 6.23 µW cm−2 and 295.23 µA cm−2 for Graphene‐Pt nanocomposite included BFCs respectively. For the amperometric xanthine biosensor linear ranges were obtained in the concentration range between 5 µM and 50 µM with the RSD (n=3 for 30 µM xanthine) value of 4.28 % for plain xanthine biosensor, 3 µM and 50 µM with the RSD (n=3 for 30 µM xanthine) value of 9.37 % for Graphene‐Ag, 5 µM to 20 µM with the RSD (n=3 for 5 µM xanthine) value of 9.00 % and 30 µM to 70 µM with the RSD (n=3 for 30 µM xanthine) value of 8.80 % for Grapehene‐Au and 1 µM and 70 with the the RSD (n=3 for 30 µM xanthine) value of 2.59 % for Grapehene‐Pt based xanthine biosensors respectively.

Novel amperometric xanthine biosensor based on xanthine oxidase immobilized on electrochemically polymerized 10-[4H-dithieno(3,2-b:2′,3′-d)pyrrole-4-yl]decane-1-amine film

In this paper, a novel amperometric xanthine (X) biosensor is constructed by xanthine oxidase (XOx) immobilization on the pencil graphite electrode (PGE). Xanthine oxidase is immobilized using glutaraldehyde (GA) on the electrochemically polymerized conducting polymer film. The detection of xanthine is based on its consumed amount due to the enzymatic reaction of xanthine oxidase. The effects of polymer thickness, applied potential, pH, and temperature were investigated and optimum parameters were found to be five cycles, +5V, +0.5V and 30°C, respectively. Storage stability, operation stability of the enzyme electrode, and effect of interferant substances on the amperometric response were also studied. In order to verify the applicability of proposed biosensor, fabricated electrode was used to measure the xanthine concentration in chicken meat samples. The present xanthine biosensor with high selectivity, sensitivity, and stability is promising for practical applications.

Electrochemical biosensor based on REGO/Fe3O4 bionanocomposite interface for xanthine detection in fish sample

In this study, xanthine molecules which can serve as an indicator of meat spoilage were determined using a novel and sensitive amperometric xanthine biosensor. Biosensor was developed by preparing a nanocomposite film that was constructed by embedding reduced expanded graphene oxide (REGO) sheets decorated with iron oxide (Fe3O4) nanoparticles into poly(glycidyl methacrylate-co-vinylferrocene) (P(GMA-co-VFc)) phase, and by covalent immobilization of Xanthine oxidase (XOD) on the surface of P(GMA-co-VFc)/REGO-Fe3O4 nanocomposite film. Bio-analytical optimal experimental conditions such as response time, linear range, operation and storage stability, working pH and temperature were studied. Current response of linear range was detected in the range of 2–36 μM with a sensitivity of 0.17 μA/M, response time of ∼3 s, and detection limit of 0.17 μM. The resulting bio-nanocomposite xanthine biosensor was subjected to fish real sample testings where 5, 8, 10, 13, 15, and 20 days-old fish samples’ xanthine content was measured. The developed biosensor was found to be applicable to real samples as a very reliable fish freshness controlling technique.

A method for determination of xanthine in meat by amperometric biosensor based on silver nanoparticles/cysteine modified Au electrode

A method is described for construction of an amperometric xanthine biosensor based on covalent Immobilization of xanthine oxidase (XOD) onto citrate capped silver nanoparticles deposited on Au electrode surface through cysteine self assembled monolayers (SAM). The biosensor showed optimum response within 5s at pH 7.0 and 35°C, when polarized at 0.5V vs. Ag/AgCl. The linear working range of biosensor for xanthine was from 2 to 16μM, with a detection limit of 0.15μM and sensitivity of 0.17mA/μM/cm2. The mean analytical recovery of exogenously added xanthine in fish meat extract (5g/l and 10g/l) was 96.2±2.3% and 95.2±3.4%, respectively. Within and between batches coefficients of variation were <2.6% and <3.4%, respectively. The biosensor measured xanthine in fish, chicken, pork, and beef meat. The enzyme electrode lost 20% of its initial activity after its regular 180 uses over a period of 60 days, when stored at 4°C in dry state.

Amperometric determination of xanthine in tea, coffee, and fish meat with graphite rod bound xanthine oxidase

A method is described for construction of an amperometric xanthine biosensor based on graphite rod modified through adsorption of xanthine oxidase. Enzymatically produced H2O2 from xanthine was split into 2H+ + O2 + 2e− at 0.6 V and the current was measured, which was directly proportional to xanthine concentration ranging from 1 ° 10−7 to 6 ° 10−7 M with a detection limit of 1 ° 10−7 M. The biosensor exhibited optimum response within 35 sec at pH 7.0 and 35°C. It was employed for determination of xanthine in tea leaves (0.9 ° 10−5−2.5 ° 10−5 mmol/g), coffee powder (3.2 μmol/g) and fish meat (90 mmol/g). The content of xanthine in fish meat increased 6.5 times with its storage at room temperature during 15 days. The enzyme electrode could be reused 200 times during the span of 30 days, when stored in reaction buffer at 4°C.

FABRICATION OF AN AMPEROMETRIC XANTHINE BIOSENSOR BASED ON POLYVINYLCHLORIDE MEMBRANE

ABSTRACT A method is described for fabrication of an amperometric xanthine biosensor based on polyvinylchloride (PVC) membrane bound xanthine oxidase (XOD). The membrane bound enzyme oxidizes xanthine into uric acid and H2O2, which is split into 2H++O2+2e- at high potential (0.4V) and measured as current (mA).Sensor showed optimum response within 30 s, at pH 7.0 and 35C. A linear relationship was observed between current and xanthine concentration ranging from 0.025 to 0.4 × 10-6 M, Km for xanthine and Imax were 0.45 × 10-6 M and 0.002 mA, respectively. Minimum detection limit of the biosensor was 2.5 × 10-8 M. Biosensor was utilized for determination of xanthine in fish meat cow and buffalos milk. Biosensor was used 100 times over a period of 45 days with only 30% loss of initial activity, when stored at 4C. PRACTICAL APPLICATIONS Evaluation of fish meat freshness is of great significance in food industries for the quality control of fish products. After the death of a fish, xanthine is a major metabolite in the degradation of adenosine triphosphate in the fish meat. Thus, xanthine attracts much attention as an indicator for estimating fish freshness. Moreover, the content of xanthine in human body fluids can also provide useful index for certain pathologic state, especially for xanthinuria.

Construction and application of an amperometric xanthine biosensor based on zinc oxide nanoparticles–polypyrrole composite film

Zinc oxide nanoparticles (ZnO-NPs) were synthesized from zinc nitrate by simple and efficient method in aqueous media at 55 °C without any requirement of calcinations step. A mixture of ZnO-NPs and pyrrole was eletropolymerized on Pt electrode to form a ZnO-NPs–polypyrrole (PPy) composite film. Xanthine oxidase (XOD) was immobilized onto this nanocomposite film through physiosorption. The ZnO-NPs/polypyrrole/Pt electrode was characterized by Fourier transform infrared (FTIR), cyclic voltammetry (CV), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical impedance spectroscopy (EIS) before and after immobilization of XOD. The XOD/ZnO-NPs–PPy/Pt electrode as working electrode, Ag/AgCl as reference electrode and Pt wire as auxiliary electrode were connected through a potentiostat to construct a xanthine biosensor. The biosensor exhibited optimum response within 5 s at pH 7.0, 35 °C and linearity from 0.8 μM to 40 μM for xanthine with a detection limit 0.8 μM (S/E = 3). Michaelis Menten constant ( K m) for xanthine oxidase was 13.51 μM and I max 0.071 μA. The biosensor measured xanthine in fish meat and lost 40% of its initial activity after its 200 uses over 100 days, when stored at 4 °C.

Disposable amperometric biosensors based on xanthine oxidase immobilized in the Prussian blue modified screen-printed three-electrode system

The screen-printed three-electrode system was applied to fabricate a new type of disposable amperometric xanthine oxidase biosensor. Carbon-working, carbon-counter and Ag/AgCl reference electrodes were all manually printed on the polyethylene terephthalate substrate forming the screen-printed three-electrode system by the conventional screen-printing process. As a mediator, Prussian blue could not only catalyze the electrochemical reduction of hydrogen peroxide produced from the enzyme reaction, but also keep the favorable potential around 0 V. The optimum operational conditions, including pH, potential and temperature, were investigated. The sensitivities of xanthine and hypoxanthine detections were 13.83 mA/M and 25.56 mA/M, respectively. A linear relationship was obtained in the concentration range between 0.10 μM and 4.98 μM for xanthine and between 0.50 μM and 3.98 μM for hypoxanthine. The small Michaelis-menten constant value of the xanthine oxidase biosensor was calculated to be 3.90 μM. The results indicate that the fabricated xanthine oxidase biosensor is effective and sensitive for the detection of xanthine and hypoxanthine.

Design of an amperometric xanthine biosensor based on a graphite transducer patterned with noble metal microparticles

Abstract A mesoporous graphite material micro-structured with palladium-platinum deposits (mixed in the ratio of 70:30% Pd:Pt) has been used as a cost-effective electrode material for designing an amperometric biosensor for xanthine. The here reported biosensor shows significantly improved operational parameters as compared to previously published results. At a constant applied potential of −0.05 V (vs. Ag/AgCl) it is distinguished with enhanced selectivity of the determination: at the working potential the current from the electrochemical transformation of various electrochemically active substances usually attending biological fluids (incl. uric acid, L-ascorbic acid, glutathione and paracetamol) has been eliminated. The effect of both the temperature and buffer composition on the analytical performance of the sensor has been investigated. Under optimal operational conditions (25°C, −0.05 V vs. Ag/AgCl, phosphate buffer, pH 8.4), the following have been defined for the biosensor: sensitivity 0.39 µA µM−1, strict linearity of the response up to xanthine concentration 70 µM, detection limit of 1.5 µM (S/N=3) and a response time of at most 60 s.

Fabrication of amperometric xanthine biosensors based on direct chemistry of xanthine oxidase

The construction of amperometric xanthine biosensor by immobilization of xanthine oxidase (XOD) on the multi-wall carbon nanotubes (CNTs) modified glassy carbon (GC) electrode surface was investigated. The direct chemistry of XOD was accomplished and the formal potential was about − 0.465 V (vs SCE). The heterogeneous electron transfer rate constant was evaluated to be 2.0 ± 0.3 s − 1 . The xanthine biosensor based on XOD entrapped in silica sol–gel (SG) thin film on CNTs-modified GC electrode surface was also investigated. The XOD still maintains its activity to xanthine. The amperometric response to xanthine showed a linear relation in the range from 0.2 µM to 10 µM and a detection limit of 0.1 µM (S/N = 3). The enzyme electrode retained 95% of its initial activity after 90 days of storage. The sensor exhibited high sensitivity, rapid response and good long-term stability.

The preparation of amperometric xanthine sensors based on multilayer thin films containing xanthine oxidase

An amperometric xanthine biosensor was prepared by immobilizing xanthine oxidase (XOx) on the surface of a platinum (Pt) disk electrode. The Pt electrode was first covered with a polyelectrolyte multilayer (PEM) film composed of poly(allylamine hydrochloride) (PAH) and poly(vinyl sulfate) (PVS) to block the Pt surface from the access of uric acid, a reaction product of the XOx-catalyzed oxidation reaction of xanthine, because uric acid can be electrochemically oxidized on the Pt electrode to induce interference. The PEM film-covered Pt electrode was further modified with a XOx-containing multilayer film composed of XOx and poly(dimethyldiallylammonium chloride) (PDDA). The xanthine biosensors thus prepared can be used successfully for detecting xanthine in the concentration range of 3–300 μM. The output current of the sensors depended on the number of the XOx/PDDA layers in the film. The PAH/PVS layer was effective to eliminate the uric acid interference.

An amperometric xanthine oxidase enzyme electrode based on hydrogen peroxide electroreduction.

A xanthine oxidase enzyme electrode (xanthine oxidase immobilized on electrochemically modified graphite and conveniently coated with gelatine electrode working surface) for quantitative analysis of xanthine is proposed. The detection of thus developed electrochemical system is based on the electroreduction of hydrogen peroxide generated in enzyme layer and offered L-ascorbic and uric acid reducing interference effect on the substrate determination. At a working potential -50 mV (vs. Ag/AgCl) the detection limit of 4.5 microM and the linearity of the amperometric signal up to substrate concentration of about 40 microM were found. At that working potential, the electrode is practically inert towards L-ascorbic- and uric acid present. The response time did not exceed 2 min.

Application of biotin-streptavidin technology in developing a xanthine biosensor based on a self-assembled phospholipid membrane

We have designed an amperometric xanthine minibiosensor based on a supported biotinylated phospholipid membrane. To this membrane streptavidin-modified xanthine oxidase was coupled. The fabricated biosensor corresponds in shape and size to a needle of 0·3 mm in diameter. The assay is based on the electrochemical detection of enzymatically generated hydrogen peroxide. The response to xanthine was linear up to 1 mmol.l −1 with a detection limit of 0·02 mmol.l −1. The response time was less than one minute and the biosensor was stable for at least five days.