Amperometric determination of ammonium with bienzyme/poly(carbamoyl) sulfonate hydrogel-based biosensor

A bienzyme sensor for the amperometric determination of ammonium (NH4+) was constructed by immobilizing glutamate oxidase (GXD, E.C. 1.4.3.11) and glutamate dehydrogenase (GIDH. E.C. 1.4.1.2) on a Clark-type oxygen electrode, The enzymes were entrapped by a poly(carbamoyl) sulfonate (PCS) hydrogel on a Teflon membrane. GIDH consumes ammonium for specific amination of 2-oxoglutarate in the presence of NADH. GXD consumes dissolved oxygen for the oxidative deamination of glutamate produced by GIDH. Dissolved oxygen acts as an essential material for GXD during its enzymatic reactions. Therefore, a signal detected as the maximum rate of the consumption of dissolved oxygen by GXD, was observed in the measurement of ammonium. A Teflon membrane was used to fabricate the biosensor in order to avoid interferences from real samples. The biosensor has a fast response (2 s) and short recovery time (2 min), The total test time for a measurement by using this ammonium biosensor (4 min) was faster than using a commercial ammonium testing kit (up to 20 min). The biosensor has a linear range between 10 and 300 μ m ammonium, with a detection limit of 2.06 μ M. A good agreement (R-2 = 0,9984) with a commercial ammonium testing kit was obtained in the measurement of wastewater sample. © 2004 Elsevier B.V. All rights reserved

Amperometric biosensor for rapid determination of alanine

An enzyme Clark electrode containing three different enzymes was developed for the determination of alanine. This sensor is based on specific dehydrogenation of L-alanine dehydrogenase (AlaDH) in combination with salicylate hydroxylase (SHL) and pyruvate oxidase (PyOD). The enzymes were entrapped by a poly(carbamoyl) sulfonate (PCS) hydrogel on a Teflon membrane. The principle of the determination scheme is as follows: the specific detecting enzyme, AlaDH, catalyses the specific dehydrogenation of alanine consuming NAD(+). The products, NADH and pyruvate, initiate two following reactions: SHL catalyzes the irreversible decarboxylation and the hydroxylation of salicylate in the presence of oxygen and NADH and PyOD decarboxylates pyruvate in the presence of oxygen and phosphate. SHL and PyOD force the equilibrium of dehydrogenation of alanine by AlaDH to the product side by consuming NADH and pyruvate, respectively. Dissolved oxygen acts as an essential material for both PyOD and SHL during their respective enzymatic reactions. This results in an amplified signal due to the two-enzymatic consumptions of dissolved oxygen in the measurement of alanine. Interferences from different amino acids and electroactive substance were found to be minimal due to the specificity of AlaDH and the application of a Teflon membrane. The sensor has a fast response (2 s) and short recovery times (2 min) with a linear range between 10 and 800 muM alanine and a detection limit of 7.2 muM. A good agreement (R-2 = 0.9902) with spectrophotometric method was obtained in beverage sample measurements. (C) 2004 Elsevier B.V. All rights reserved

An amperometric biosensor for determining amino acids using a bienzymatic system containing amino acid oxidase and protease

An amperometric biosensor for rapid determination of the concentration of L-amino acids has been developed using L-amino acid oxidase (L-AAO) immobilized by gel entrapment with poly( carbamoyl) sulfonate hydrogel. The broad substrate range of L-AAO allows this biosensor to be flexible in application. The artificial sweetener, aspartame, was determined by coupling L-AAO with pronase

Amperometric determination of lactate with novel trienzyme/poly(carbamoyl) sulfonate hydrogel-based sensor

A novel trienzyme sensor for the amperometric determination of lactate was constructed by immobilizing salicylate hydroxylase (SHL, E.C. 1.14.13.1), L-lactate dehydrogenase (LDH, E.C. 1.1.1.27), and pyruvate oxidase (PyOD, E.C. 1.2.3.3) on a Clark-type oxygen electrode. The enzymes were entrapped by a poly(carbamoyl) sulfonate (PCS) hydrogel on a Teflon membrane. LDH catalyzes the specific dehydrogenation of lactate consuming NAD+. SHL catalyzes the irreversible decarboxylation and the hydroxylation of salicylate in the presence of oxygen and NADH produced by LDH. PyOD decarboxylates pyruvate using oxygen and phosphate. SHL and PyOD force the equilibrium of dehydrogenation of lactate by LDH to the product side by consuming NADH and pyruvate, respectively. Dissolved oxygen acts as an essential material for both PyOD and SHL during their respective enzymatic reactions. Therefore, an amplified signal, caused by the consumptions of dissolved oxygen by the two enzymes, was observed in the measurement of lactate. Regeneration of cofactor was found in the trienzyme system. A Teflon membrane was used to fabricate the sensor in order to avoid interferences. The sensor has a fast response (2 s) and short recovery times (2 min). The total test time for a measurement by using this lactate sensor (4 min) was faster than using a commercial lactate testing kit (up to 10 min). The sensor has a linear range between 10 and 400 muM lactate, with a detection limit of 4.3 muM. A good agreement (R-2 = 0.9984) with a commercial lactate testing kit was obtained in beverage sample measurements. (C) 2004 Elsevier B.V. All rights reserved

A salt-tolerant yeast-based microbial sensor for 24 hour community wastewater monitoring in coastal regions

A microbial sensor for rapid determination of the concentration of biodegradable pollutants in wastewater has been developed using the salt-tolerant yeast Arxula adeninivorans LS3 immobilized by gel entrapment with poly (carbamoyl) sulfonate hydrogel (PCS gel) on a Clark-type oxygen electrode. This sensor needs 5 min for every measurement instead of 5 days for BOD5. The sensor has a linear response of up to 550 mg L-1 BOD with a correlation of coefficient R-2 = 0.9785. The detection limit was calculated to be 2.1 mg L-1 BOD equivalents, and the determination limit was 6.0 mg L-1 BOD equivalents. The high tolerance to salt of the Arxula adeninivorans LS3 strain prevents the inactivation of cells caused by the seawater from affecting the measurements. In a 24-hour comparative study using real wastewater samples from an international college situated in Hong Kong, the microbial sensor showed a very good correlation (R-2 = 0.9134) with the standard BOD5 method and truly reflected the `life cycle' of the college people. The microbial sensor allows almost ideal real-time monitoring in water pollution and degradation

Comparing the use of blogs and Facebook in supporting knowledge management in student placement

Paper PresentationSymposium Theme: Learning without Limits?Track: Technology-Supported Professional LearningParallel Session 2Although prior studies showed that blogs and Facebook could probably support knowledge management in experience capture and information dissemination (Stiler & Philleo, 2003), very few studies have been done to investigate, compare and contrast the knowledge management process using blogs and Facebook despite the differences in how social interactions are conducted in the two social media platforms. This study aims at addressing such a gap by adopting a mixed method research design which includes a qualitative content analysis of blogs/Facebook entries and a quantitative comparison of user perception

A screen-printed biosensor using pyruvate oxidase for rapid determination of phosphate in synthetic wastewater

A screen-printed phosphate biosensor based on immobilized pyruvate oxidase (PyOD, E. C. 1.2.3.3) has been developed for monitoring phosphate concentrations in a sequencing batch reactor (SBR) system. The enzyme was immobilized by a nafion matrix and covered a poly ( carbamoyl) sulfonate (PCS) hydrogel on a screen-printed electrode. PyOD consumes phosphate in the presence of pyruvate and oxygen and generates hydrogen peroxide (H2O2), carbon dioxide and acetylphosphate. The electroactive H2O2, monitored at + 420 mV vs Ag/AgCl, is generated in proportion to the concentration of phosphate. The sensor has a fast response time ( 2 s) and a short recovery period ( 2 min). The time required for one measurement using this phosphate biosensor was 4 min, which was faster than the time required using a commercial phosphate testing kit ( 10 min). The sensor has a linear range from 7.5 muM to 625 muM phosphate with a detection limit of 3.6 muM. There was good agreement (R-2 = 0.9848) between the commercial phosphate testing kit and the phosphate sensor in measurements of synthetic wastewater in a SBR system. This sensor maintained a high working stability (> 85\%) after 12 h of operation and involved a simple operation procedure. It therefore serves as a useful tool for rapid and accurate phosphate measurements in the SBR system and probably for process control

Biosensor for rapid determination of 3-hydroxybutyrate using bienzyme system

A bienzyme-based Clark electrode was developed for the determination of 3-hydroxybutyrate. This sensor is based on the specific dehydrogenation by 3-hydroxybutyrate dehydrogenase (HBDH, E.C. 1.1.1.30) in combination with salicylate hydroxylase (SHL E.C. 1.14.13.1). The enzymes were entrapped by a poly(carbamoyl) sulfonate (PCS) hydrogel on a Teflon membrane. The principle of the determination scheme is as follows: the specific detecting enzyme, HBDH, catalyses the specific dehydrogenation of 3-hydroxybutyrate consuming NAD(+). The products, NADH, initiate the irreversible decarboxylation and the hydroxylation of salicylate by SHL in the presence of oxygen. SHL forces the equilibrium of dehydrogenation of 3-hydroxybutyrate by HBDH to the product side by consuming NADH. Dissolved oxygen acts as an essential material for SHL during its enzymatic reactions. This results in a detectable signal due to the SHL-enzymatic consumptions of dissolved oxygen in the measurement of 3-hydroxybutyrate. Interferences from different amino acids and electroactive substances were found to be minimal due to the specificity of HBDH and the application of a Teflon membrane. The sensor has a fast response (2 s) and short recovery time (2 min) with a linear range between 8 and 800 mu M 3-hydroxybutyrate and a detection limit of 3.9 mu M. A good agreement (R-2 = 0.9925) with theoretical calculation was obtained in spiked serum sample measurements. (c) 2005 Elsevier B.V. All rights reserved

Amperometric biosensor for determining human salivary phosphate

An amperometric biosensor was constructed for analysis of human salivary phosphate without sample pretreatment. The biosensor was constructed by immobilizing pyruvate oxidase (PyOD) on a screen-printed electrode. The presence of phosphate in the sample causes the enzymatic generation of hydrogen peroxide (H2O2), which was monitored by a potentiostat and was in proportion to the concentration of human salivary phosphate. The sensor shows response within 2 s after the addition of standard solution or sample and has a short recovery time (2 min). The time required for one measurement using this phosphate biosensor was 4 min, which was faster than the time required using a commercial phosphate testing kit (10 min). The sensor has a linear range from 7.5 to 625 mu M phosphate with a detection limit of 3.6 mu M. A total of 50 salivary samples were collected for the determination of phosphate. A good level of agreement (R-2 = 0.9646) was found between a commercial phosphate testing kit and the phosphate sensor. This sensor maintained a high working stability (>85\%) after 12 h operation and required only a simple operation procedure. The amperometric biosensor using PyOD is a simple and accurate tool for rapid determinations of human salivary phosphate, and it explores the application of biosensors in oral and dental research and diagnosis. (C) 2005 Elsevier Inc. All rights reserved