Uric acid sensor

S. Uchiyama, H. Shimizu, and Y. Hasebe, Chemical amplification of uric acid sensor responses by dithiothreitol. Anal. Chem., 66, 1873-1876 (1994). 

New developments in this area include uric acid sensors based on the mediation of urate oxidase by a novel redox polymer, poly(N-methyl-o-phenylenediamine) [145], and by the freely diffusing mediator 1-methoxy-5-methylphenazinium [146], continued research on the direct amperometric detection of NADH [147] and the use of redox mediators [148] for dehydrogenase enzymes, to allow practical sensors that exploit this large class of enzymes, and the use of cytochrome P450-modified glassy carbon electrodes as drug metabolism biosensors [149]. 

Wang YT, Yu L, Zhu ZQ, Zhang J, Zhu JZ (2009) Novel uric acid sensor based on enzyme electrode modifled by ZnO nanoparticles and multiwall carbon nanotubes. Anal Lett 42 775-789... 

An amperometric urate sensor based on uricase-immobilized silk fibroin membrane was developed by Zhang [256], The biosensor can be used to measure the urate level in human serum or urine and standard additions of uric acid. F or this biosensor, the recoveries of uric acid in human serum and urine are in the range of 94.2 102.6% to 92.5 97.9%, respectively. The relative standard deviations for repeatedly monitoring standard urate solution, human serum, and urine are 2.37, 3.72, and 2.95%, respectively, based on 100 measurements. 

For the assay of uric acid, a sensor based on KMn04-octylphenyl polyglycol ether is proposed [88], Uric acid can be assayed directly in urine in the 0.10— 600- ag/mL concentration range with a detection limit of 55 ng/mL. The system is free of interferences. 

Biosensors are also available for glucose, lactate, alcohol, sucrose, galactose, uric acid, alpha amylase, choline, and L-lysine. All are amperometric sensors based on O2 consumption or H2O2 production in conjunction with the turnover of an enzyme in the presence of substrate. In the case of glucose oxidase reaction, the normal biological reaction is ... 

How analytical methods deal with interferences is one of the more ad hoc aspects of method validation. There is a variety of approaches to studying interference, from adding arbitrary amounts of a single interferent in the absence of the analyte to establish the response of the instrument to that species, to multivariate methods in which several interferents are added in a statistical protocol to reveal both main and interaction effects. The first question that needs to be answered is to what extent interferences are expected and how likely they are to affect the measurement. In testing blood for glucose by an enzyme electrode, other electroactive species that may be present are ascorbic acid (vitamin C), uric acid, and paracetamol (if this drug has been taken). However, electroactive metals (e.g., copper and silver) are unlikely to be present in blood in great quantities. Potentiometric membrane electrode sensors (ion selective electrodes), of which the pH electrode is the... 

C.A. Marquette, M.F. Lawrence and L.J. Blum, DNA covalent immobilization onto screen-printed electrode networks for direct label-free hybridization detection of p53 sequences, Anal. Chem., 78 (2006) 959-964. J.-M. Zen, Y.-Y. Lai, H.-H. Yang and A.S. Kumar, Multianalyte sensor for the simultaneous determination of hypoxanthine, xanthine and uric acid based on a preanodized nontronite-coated screen-printed electrode, Sens. Actuators B Chem., 84 (2002) 237-244. 

J.-C. Chen, H.-H. Chung, C.-T. Hsu, D.-M. Tsai, A.S. Kumar and J.-M. Zen, A disposable single-use electrochemical sensor for the detection of uric acid in human whole blood, Sens. Actuators B Chem., 110 (2005) 364r-369. 

For example, a typical UMB (enzyme only) has an 80 pA response to a sample of 5 mM glucose. The same sensor has a response of 900 pA to 0.44 mM uric acid, 180 pA response to 0.21 mM acetaminophen, and 140 pAto 0.11 mM ascorbic acid (these are maximum clinical amounts of each of the three major interferences that could be found in human serum). The total response due to interferences is more than fifteen times that of the response due to an average clinical amount of glucose. 

UMBsact as working electrodes, and the recorded current would be the sum for all four. A sensor was considered useful as long as the total signal due to the three interferences (uric acid, acetaminophen, and ascorbic acid) was less than 5% of the signal for 5 mM glucose. One ultramicrobiosensor with poly( 1,3-DAB) had a useful lifetime of up to four weeks. 

Electrochemical transducers work based on either an amperometric, potentio-metric, or conductometric principle. Further, chemically sensitive semiconductors are under development. Commercially available today are sensors for carbohydrates, such as glucose, sucrose, lactose, maltose, galactose, the artificial sweetener NutraSweet, for urea, creatinine, uric acid, lactate, ascorbate, aspirin, alcohol, amino acids and aspartate. The determinations are mainly based on the detection of simple co-substrates and products such as 02, H202, NH3, or C02 [142]. 

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