Novel, reagentless, amperometric biosensor for uric acid based on a chemically modified screen-printed carbon electrode coated with cellulose acetate and uricase

Abstract

Amperometry in stirred solution has been used for the systematic evaluation of modified screen-printed carbon electrodes (SPCEs) with a view to developing a reagentless biosensor for uric acid. The developed system consists of a base cobalt phthalocyanine (CoPC) electrode tailored to the electrocatalytic oxidation of H2O2 by means of a cellulose acetate (CA)-uricase bilayer. Uricase was immobilized by drop-coating the enzyme onto the CA membrane covering the CoPC-SPCE. The device exploits the near-universal H2O2-generating propensity of oxidases, the permselectivity of the CA film towards H2O2 and the electrocatalytic oxidation of this product at the CoPC-SPCE. The electrochemical oxidation of the resulting Co+ species was used as the analytical signal, facilitating the application of a greatly reduced operating potential when compared with that required for direct oxidation of H2O2 at unmodified electrodes. The time required to achieve 95% of the steady-state current (t95i(ss)) was 44 s [relative standard deviation = 7.5% (n = 10)]. Amperometric calibrations were linear over the range from 13 x 10(-6) to 1 x 10(-3) mol dm-3, with the former representing the limit of detection. The CA membrane extended the linear range of the biosensor by over two orders of magnitude, when apparent Michaelis-Menten constants (Km') of immobilized and free enzymes are compared. This suggests that the process is diffusion-controlled and not governed by the kinetics of the enzyme. The precision of electrode fabrication was determined by cyclic voltammetry to be 4.9% (n = 6).(ABSTRACT TRUNCATED AT 250 WORDS)

Voltammetric Behavior and Trace Determination of Lead at a Mercury-Free Screen-Printed Carbon Electrode

“…It has previously been shown that our unmodi®ed SPCEs demonstrate good electron transfer characteristics and have been successfully employed for the measurement of triclosan (a phenolic species) in mouthwash and toothpaste products by stripping voltammetry [6]. The same electrodes were applied to the oxidative measurement of paracetamol [7] and uric acid [8]. It should also be noted that other workers have successfully used the same ink, containing a ligand, for the fabrication of a sensor for Ni [9].…”

Electrochemical Detection of Uric Acid in Mixed and Clinical Samples: A Review

“…Other methods includes, high performance liquid chromatography on reversed phase columns along with detection by either UV absorbance or mass spectrometry (MS) [25]. Each of these methods involves multiple reaction steps including serum preparation, various sample preparation steps and eventually require either spectroscopic methods to identify the product [26,27] or an enzyme cascade technique which indirectly determines the concentration of the H 2 O 2 intermediate [28]. Also in these assays the blood sample has to be converted into denatured serum as coagulated blood particles tend to create erroneous detection signals.…”

An Inexpensive Biosensor for Uric Acid Determination in Human Serum by Flow-Injection Analysis

“…In the first approach the O 2 consumption or the H 2 O 2 formed is usually monitored while in the second the peroxidase consumption of H 2 O 2 produced in the enzymatic oxidation of uric acid is determined. However, the construction procedures described usually requires time consuming enzyme immobilization procedures [3,7,8], are of relative complex preparation or exhibit lack of robustness [4 -7, 9 -11], and are applied to real sample analysis in a manual batch fashion. Moreover the analytical benefits of the above-mentioned preparations is questionable since some of these electrodes are still capable to oxidize another analytes present in serum samples, or exhibit slow responses [3,4] and short useful lifetime [3,7,11].…”