Detection Of Xanthine Research Articles

Application of Bismuth(III)-Entrapped XO Biosensing System for Xanthine Determination in Beverages

A xanthine biosensor was prepared by electrochemical immobilization of xanthine oxidize enzyme onto carbon paste electrode via entrapment of Bi3+. After the optimization of experimental parameters, analytical characteristics were investigated. Two linear ranges between 0.02 and 0.06 and 1–7.5 μM with the equation y = 93.00x + 0.12 and y = 1.07x + 18.03 with the correlation coefficients of R2 = 0.9951 and R2 = 0.9931, respectively, were obtained for this biosensing system. RSD value was calculated for 0.04 μM xanthine (n = 5) and found as 3.84%. LOD and LOQ values were also calculated and revealed as 1.30 × 10−8 and 4.3 × 10−8 M, respectively. Then, this biosensor was applied for xanthine detection in real samples. As a sample treatment, only necessary dilutions were made. Four types of beverages including wine, energy drink, peach, and sour cherry juice were used for this purpose. Obtained recovery values demonstrate that this system is applicable for xanthine detection in real samples without needing any laborious sample pretreatment procedures.

Electrochemical detection of xanthine in fish meat by xanthine oxidase immobilized on carboxylated multiwalled carbon nanotubes/polyaniline composite film

A commercial xanthine oxidase (XOD) was immobilized covalently onto carboxylated multiwalled carbon nanotubes (c-MWCNT) and polyaniline (PANI) composite film electrodeposited on the surface of a Pt electrode, using N-ethyl-N′-(3-dimethyl aminopropyl) carbodiimide (EDC) and N-hydroxy succinimide (NHS) chemistry. A xanthine biosensor was fabricated using XOD/c-MWCNT/PANI/Pt electrode as a working electrode, Ag/AgCl (3 M KCl) as standard electrode and Pt wire as auxiliary electrode connected through a potentiostat. The enzyme electrode was characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectrophotometry and electrochemical impedance spectroscopy (EIS). The biosensor showed optimum response within 4 s at pH 7.0 and 35 °C, when polarized at 0.4 V. The optimized xanthine biosensor showed linear response range of 0.6–58 μM, with a detection limit of 0.6 μM (S/N = 3), and a correlation coefficient of 0.98. The biosensor was applied to determine xanthine in fish meat. The biosensor lost 50% of its initial activity after its 200 uses over a period of 100 days.

Amperometric xanthine biosensors based on electrodeposition of platinum on polyvinylferrocenium coated Pt electrode

Novel xanthine biosensors were successfully fabricated by immobilizing xanthine oxidase on polyvinylferrocenium perchlorate matrix (PVF+ClO4−) and platinum electrodeposited polyvinylferrocenium perchlorate matrix. PVF+ClO4− film was coated on Pt electrode at +0.7 V vs. Ag/AgCl by electrooxidation of polyvinylferrocene (PVF). Platinum nanoparticles were deposited on PVF+ClO4− electrode by electrochemical deposition in 2.0 mM H2PtCl6 solution at −0.2 V. Xanthine oxidase was incorporated into the polymer matrix via ion exchange process by immersing modified Pt electrodes in the enzyme solution. The amperometric responses of the biosensors were measured via monitoring oxidation current of hydrogen peroxide at +0.5 V. Under the optimal conditions, the linear ranges of xanthine detection were determined as 1.73 × 10−3–1.74 mM for PVF+XO− and 0.43 × 10−3–2.84 mM for PVF+XO−/Pt. The detection limits of xanthine were 5.20 × 10−4 mM for PVF+XO− and 1.30 × 10−4 mM for PVF+XO−/Pt. Moreover, the effects of applied potential, electrodeposition potential, H2PtCl6 concentration, amount of electrodeposited Pt nanoparticles, thickness of polymeric film, temperature, immobilization time, xanthine and xanthine oxidase concentrations on the response currents of the biosensors were investigated in detail. The effects of interferents, the operational and storage stabilities of biosensors and the applicabilities to drug samples of the biosensors analysis were also evaluated.

BSA-stabilized Au clusters as peroxidase mimetics for use in xanthine detection

In this paper, we demonstrated that bovine serum albumin (BSA) stabilized Au clusters exhibited highly intrinsic peroxidase-like activity. Unlike nature enzymes, the BSA-Au clusters have strong robustness and can be used over a wide range of pH and temperature. Because of ultra-small size, good stability and high biocompatibility in water solution compare with other kinds of nanoparticles as peroxidase mimetics, such as Fe 3O 4, FeS or graphene oxide, it is more competent for bioanalysis. Furthermore, we make use of the novel properties of BSA-Au clusters as peroxidase mimetics to detect H 2O 2. The as-prepared BSA-Au clusters were used to catalyze the oxidation of a peroxidase substrate 3,3,5,5-tetramethylbenzidine (TMB) by H 2O 2 to the oxidized colored product, and which provides a colorimetric detection of H 2O 2. As low as 2.0 × 10 −8 M H 2O 2 could be detected with a linear range from 5.0 × 10 −7 to 2.0 × 10 −5 M via this method. More importantly, a sensitive and selective method for xanthine detection was developed using xanthine oxidase (XOD) and the as-prepared BSA-Au clusters. The detection limit of this assay for xanthine was 5 × 10 −7 M and the proposed method was successfully applied for the determination of xanthine in urine and human serum sample.

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.

Sensitive and selective xanthine amperometric sensors based on calcium carbonate nanoparticles

Using calcium carbonate nanoparticles as enzyme immobilization matrix, the developments of xanthine biosensor were achieved by both electrooxidation and electroreduction of the enzymatic-generated hydrogen peroxide based on xanthine oxidase (XnOx) and horseradish peroxidase (HRP). Amperometric detection of xanthine was evaluated by holding the modified electrode at 0.55 and −0.05 V (versus SCE), for XnOx/Nano-CaCO 3 and XnOx/HRP/Nano-CaCO 3, respectively. The linear dynamic ranges of anodic and cathodic detections of xanthine were between 2 × 10 −6 to 2.5 × 10 −4 M and 4 × 10 −7 to 5 × 10 −5 M, respectively. The detection limits were determined to be of 2 × 10 −6 and 1 × 10 −7 M with anodic and cathodic processes, respectively. At lower working potential, XnOx/HRP/Nano-CaCO 3/GCE bienzymatic system exhibited excellent selectivity; the bienzyme electrode was inert towards ascorbic and uric acid present. Moreover, the permeability of enzyme/Nano-CaCO 3 was evaluated by the use of rotating disk electrode voltammetry.

Immobilization of a trienzymatic system in a sol–gel matrix: A new fluorescent biosensor for xanthine

In this work we report the development of a highly sensitive fluorescent multienzymatic biosensor for quantitative xanthine detection. This biosensor is built by the simultaneous encapsulation of three enzymes, xanthine oxidase, superoxide dismutase and peroxidase, in a single sol–gel matrix coupled to the Amplex Red probe. The sol–gel chemistry yields a porous, optically transparent matrix that retains the natural conformation and the reactivity of the three co-immobilized proteins. Xanthine determination is based on a sequence of reactions, namely catalytic oxidation of xanthine to uric acid and superoxide radical, and subsequent catalytic dismutation of the radical, resulting in the formation of hydrogen peroxide, which reacts stoichiometrically with non-fluorescent Amplex Red to produce highly fluorescent resorufin. The optimal operational conditions for the biosensor were investigated. Linearity was observed for xanthine concentrations up to 3.5 μM, with a detection limit of 20 nM, which largely improved the sensitivity of the current xanthine biosensors. The developed biosensor is reusable and remains stable for 2 weeks under adequate storage conditions.

Development of a high analytical performance-xanthine biosensor based on layered double hydroxides modified-electrode and investigation of the inhibitory effect by allopurinol

The determination of xanthine has considerable importance in clinical and food quality control. Therefore, in this present work, we developed a novel xanthine biosensor based on immobilization of xanthine oxidase (XnOx) by attractive materials layered double hydroxides (LDHs). Amperometric detection of xanthine was evaluated by holding the modified electrode at 0.55 V (versus saturated calomel electrode (SCE)). Due to the special properties of LDHs, such as chemical inertia, mechanical and thermal stability, anionic exchange ability, high porosity and swelling properties, XnOx/LDHs-modified electrode exhibited a developed analytical performance. The biosensor provided a linear response to xanthine over a concentration range of 1 × 10 −6 M to 2 × 10 −4 M with a sensitivity of 220 mA M −1 cm −2 and a detection limit of 1 × 10 −7 M based on S/N = 3. In addition, the immobilized XnOx layers have been characterized using atomic force microscopy under both air atmosphere and liquid environment, which exhibited the interesting swelling phenomenon of LDHs. The investigation of inhibition of XnOx by allopurinol was carried out using this XnOx/LDHs-modified electrode. The experimental results indicated that inhibitory effect could be achieved by allopurinol with a quasi-reversible competitive type.