Xanthine Biosensor Research Articles

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.

Xanthine Sensors Based on Anodic and Cathodic Detection of Enzymatically Generated Hydrogen Peroxide

AbstractA xanthine biosensor was fabricated by the covalent immobilization of xanthine oxidase (XO) onto a functionalized conducting polymer (Poly‐5, 2′: 5′, 2″‐terthiophine‐3‐carboxylic acid), poly‐TTCA through the formation of amide bond between carboxylic acid groups of poly‐TTCA and amine groups of enzyme. The immobilization of XO onto the conducting polymer (XO/poly‐TTCA) was characterized using cyclic voltammetry, quartz crystal microbalance (QCM), and X‐ray photoelectron spectroscopy (XPS) techniques. The direct electron transfer of the immobilized XO at poly‐TTCA was found to be quasireversible and the electron transfer rate constant was determined to be 0.73 s−1. The biosensor efficiently detected xanthine through oxidation at +0.35 V and reduction at −0.25 V (versus Ag/AgCl) of enzymatically generated hydrogen peroxide. Various experimental parameters, such as pH, temperature, and applied potential were optimized. The linear dynamic ranges of anodic and cathodic detections of xanthine were between 5.0×10−6−1.0×10−4 M and 5.0×10−7 to 1.0×10−4 M, respectively. The detection limits were determined to be of 1.0×10−6 M and 9.0×10−8 M with anodic and cathodic processes, respectively. The applicability of the biosensor was tested by detecting xanthine in blood serum and urine real samples.

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.

Amperometric Study of Au‐Colloid Function on Xanthine Biosensor Based on Xanthine Oxidase Immobilized in Polypyrrole Layer

AbstractFour kinds of xanthine oxidase (XOD) based amperometric biosensors were fabricated and their analytical performances were compared. Polypyrrole (PPY)/XOD biosensor was constructed by electrochemical oxidation of pyrrole in the solution containing xanthine oxidase and pyrrole in this paper. Colloidal Au was then immobilized on the biosensor. On the other hand, electron mediator, Prussian Blue (PB), was deposited on the electrode before the immobilization of PPY/XOD to enhance electron‐transfer rate and current response. The results showed that PPY/XOD, PPY/XOD/Au‐colloid, PB/PPY/XOD and PB/PPY/XOD/Au‐colloid biosensors exhibit good response to xanthine in 1×10−6 M and 2×10−5 M and Michaelis‐Menten constants (Km) of these biosensors were 242.2, 113.4, 144.5, 43.2 μmol⋅L−1, respectively. The dependence of current responses with applied voltages was discussed, and different mechanisms of these biosensors were discussed. It has been found that colloidal Au can enhance the current response at the same concentration of xanthine solution and decrease the energy‐barrier of electron‐transfer reaction on the electrode.

Xanthine Biosensor Based on Didodecyldimethylammonium Bromide Modified Pyrolytic Graphite Electrode

AbstractThe vesicle of didodecyldimethylammonium bromide (DDAB) which contained tetrathiafulvalene (TTF) was mixed with xanthine oxidase, and the mixture was cast on the pyrolytic graphite electrode. The lipid films were used to supply a biological environment resembling biomembrane on the surface of the electrode. TTF was used as a mediator because of its high electron‐transfer efficiency. A novel xanthine biosensor based on cast DDAB film was developed. The effects of pH and operating potential were explored for optimum analytical performance by using the amperometric method. The response time of the biosensor was less than 10 s. The detection limit of the biosensor was 3.2 × 10−7 mol/L and the liner range was from 4 × 10−7 mol/L to 2.4 × 10−6 mol/L.

Fibre-optic biosensor for hypoxanthine and xanthine based on a chemiluminescence reaction

Fibre-optic biosensors were constructed for determination of hypoxanthine and xanthine. Xanthine oxidase and peroxidase were immobilized on different preactivated membranes which were subsequently mounted onto the tip of a fibre-optic bundle. The H 2O 2 generated by the reaction of hypoxanthine and xanthine oxidase was measured by chemiluminescence (CL) detection using luminol and peroxidase. A linear calibration curve of the sensors in the range of 1–316 μM hypoxanthine and 3ṡ1–216 μM xanthine, respectively, with a detection limit of 0ṡ55 μM hypoxanthine was obtained. Recovery of hypoxanthine ranged between 91 and 102%.

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.