Uric Acid Sensor Research Articles

Determination of catecholamines and uric acid in biological fluids without pretreatment, using chemically amplified biosensors

Chemically amplified biosensors based on substrate recycling using oxidase and reducing agents have been applied to the convenient detection of catecholamines and uric acid in biological fluids. These methods are based on the highly sensitive detection of trace amounts of analytes (10 −8 M level) in highly diluted (1000–10000 fold) body samples, in which the interfering species are also diluted to negligible concentration level for an amperometric measurement. The concentration of uric acid obtained by the chemically amplified uric acid sensor is in fairly good agreement with that obtained by conventional spectrophotometry.

Chemical Amplification of Uric Acid Sensor Responses by Dithiothreitol

The consumption of oxygen caused by the uricase reaction can be significantly amplified when the reaction is performed in the presence of dithiothreitol. As a result, chemically amplified current responses of uric acid using the immobilized uricase electrode were obtained. This amplified current response was increased with increasing dithiothreitol concentrations in the sample solution, and the amplification factor for a 1×10 -6 M uric acid solution was increased to 133 when 5×10 -2 M dithiothreitol solution (pH 9.1) was used. During amplification, the ESR signal of hydroxyl radicals was increased along with amplification

Development of amperometric sensors for uric acid based on chemically modified graphite–epoxy resin and screen-printed electrodes containing cobalt phthalocyanine

Cyclic voltammetry, hydrodynamic voltammetry (HDV) and amperometry were used to investigate the behaviour of uric acid at carbon(graphite)–epoxy resin electrodes modified with the following electrocatalysts: ferrocenes, phthalocyanines, phenoxazines, phenazines and hexacyanoferrate species. As no direct electrocatalytic oxidation of uric acid was apparent, enzyme-coupled mediation was studied using uricase with electrodes modified with ferrocene, cobalt phthalocyanine (CoPC) and Meldola's Blue, in the presence and absence of oxygen. Again, no electrocatalysis was observed so we exploited the specificity of the enzyme uricase, which is known to produce hydrogen peroxide from uric acid. This product has been shown to undergo electrocatalysis at modified electrodes, and preferentially traverses certain membranes, so this rationale was adopted for the ensuing studies. Cyclic voltammetry and amperometry were used to study the electrochemical behaviour of H2O2 in 0.05 mol dm–3phosphate buffer (pH 9.3). Hydrogen peroxide was found to be electroactive at substantially lower potentials (<600 mV) at CoPC-modified electrodes than at unmodified electrodes. The precision of surface–surface reproducibility of epoxy resin electrodes was calculated by cyclic voltammetry to be 7.3%(n= 5). Further studies were performed with and without cellulose acetate (CA) membranes using amperometry in stirred solution. Epoxy resin electrodes were simply dropcoated with CA. The membrane functioned as an effective barrier against a range of potential interferences, but allowed the selective detection of enzymically generated H2O2 from urate. This methodology was then translated to screen-printed electrodes (SPEs). Cyclic voltammetry was first used to establish the precision of electrode manufacture; this was 4.9%(n= 5). The SPEs were then modified by placing each inside a tube, one end of which was covered with a solvent cast (CA) membrance. This electrode–polymer configuration furnished similar permselective properties as the drop-coated devices. The solvent cast membranes were treated with various concentrations of uricase; when the membrane was loaded with 0.48 U of enzyme a measurable H2O2 signal was obtained at the CoPC–SPE for a solution containing 0.18 mmol dm–3 uric acid.

Voltammetric and amperometric behaviour of uric acid at bare and surface-modified screen-printed electrodes: studies towards a disposable uric acid sensor

Download options Please wait... Article information DOI https://doi.org/10.1039/AN9921701299 Article type Paper Download Citation Analyst, 1992,117, 1299-1303 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Voltammetric and amperometric behaviour of uric acid at bare and surface-modified screen-printed electrodes: studies towards a disposable uric acid sensor M. A. T. Gilmartin, J. P. Hart and B. Birch, Analyst, 1992, 117, 1299 DOI: 10.1039/AN9921701299 To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Markas A. T. Gilmartin John P. Hart Brian Birch

Oxidase/peroxidase bilayer-modified electrodes as sensors for lactate, pyruvate, cholesterol and uric acid

Enzyme heterobilayer-modified electrodes were fabricated by successively covalently binding to the surface of a tin(IV) oxide plate horseradish peroxidase (HRP), then an oxidase (lactate, pyruvate or cholesterol oxidase or uricase), which liberates hydrogen peroxide by reaction with the respective substrate. The cooperative action of oxidase-HRP leads to an efficient amperometric sensor system with the minimum amount of enzyme immobilized on an electrode.

A MICROBIAL SENSOR FOR URIC ACID

Abstract A microbial sensor for uric acid has been devised by coupling intact yeast cells (Pichia membranaefaciens 162300) with a carbon dioxide electrode. The resulting sensor has a markedly longer lifetime than the corresponding isolated enzyme sensor. The response slopes ranging from 37 to 42 mV per decade were obtained over the concentration range 1.0×10−4–2.5×10−3 mol dm−3 uric acid during the period 4–50 d.