Electrochemical Detection Of Uric Acid Research Articles

Electrochemical detection of uric acid using graphite screen-printed electrodes modified with Prussian blue/poly(4-aminosalicylic acid)/Uricase

This work investigates the use of electrochemical platforms containing polymeric films derived from 4-aminosalicylic acid (4-ASA) modified with the enzyme urate oxidase (UOx) for quantification of uric acid (UA) in urine samples. Electropolymerization of 4-ASA was investigated over carbon graphite electrodes (CGE). As a mediator of the enzymatic product, Prussian blue (PB) was also electrodeposited over the working electrodes. The film provides electrochemical activity with a homogeneous coverage, and the use of PB does not alter the electrochemical profile or the film morphology. Analysis of infrared spectra demonstrates the presence of the unchanged carboxyl groups and suggests that polymerization begins at the nitrogen atom. The biosensor was developed on graphite screen-printed electrodes with all optimization performed on CGE. UOx was immobilized through physical adsorption and the proposed sensor was coupled to a flow cell in a flow injection analysis (FIA) system with amperometric detection. The flow rate, injection volume, and pH of the UA solution were optimized at 2.10mLmin−1, 200μL, and 8.27, respectively. Under these conditions, a relative standard deviation of 2.15% (n=10) was achieved for UA detection. A linear range of 10 to 200μM was obtained for UA determination with a limit of detection of 3.0μM. UA recovery from amended urine samples was 97.4% (±2.4).

Simultaneously electrochemical detection of uric acid and ascorbic acid using glassy carbon electrode modified with chrysanthemum-like titanium nitride

Chrysanthemum-like titanium nitride (CL-TiN) was fabricated at 800°C through ammonia nitridation treatment of TiO2 precursor. An electrochemical biosensor based on the glassy carbon electrode modified with TiN (CL-TiN/GCE) was prepared for the simultaneously detection of ascorbic acid (AA) and uric acid (UA). Excellent results are obtained for the separate quantification of UA and AA by differential pulse voltammetry due to the special structure and large surface area of TiN. The detection limits of the electrochemical sensor are 1.52μM and 0.28μM for AA and UA (S/N=3), and the working linear ranges for AA and UA are 50–1500μM and 10–300μM, respectively. This sensor also exhibits outstanding anti-interference ability toward co-existing molecules with good stability, sensitivity and reproducibility. The present work opens a new window for simultaneous detection of AA and UA based on the CL-TiN/GCE.

Solution Process Synthesis of High Aspect Ratio ZnO Nanorods on Electrode Surface for Sensitive Electrochemical Detection of Uric Acid

This study demonstrates a highly stable, selective and sensitive uric acid (UA) biosensor based on high aspect ratio zinc oxide nanorods (ZNRs) vertical grown on electrode surface via a simple one-step low temperature solution route. Uricase enzyme was immobilized on the ZNRs followed by Nafion covering to fabricate UA sensing electrodes (Nafion/Uricase-ZNRs/Ag). The fabricated electrodes showed enhanced performance with attractive analytical response, such as a high sensitivity of 239.67 μA cm−2 mM−1 in wide-linear range (0.01–4.56 mM), rapid response time (~3 s), low detection limit (5 nM), and low value of apparent Michaelis-Menten constant (Kmapp, 0.025 mM). In addition, selectivity, reproducibility and long-term storage stability of biosensor was also demonstrated. These results can be attributed to the high aspect ratio of vertically grown ZNRs which provides high surface area leading to enhanced enzyme immobilization, high electrocatalytic activity, and direct electron transfer during electrochemical detection of UA. We expect that this biosensor platform will be advantageous to fabricate ultrasensitive, robust, low-cost sensing device for numerous analyte detection.

Porphyrin Functionalized Graphene for Sensitive Electrochemical Detection of Uric Acid

Porphyrin Functionalized Graphene for Sensitive Electrochemical Detection of Uric Acid

Ce(3+)-ion-induced visible-light photocatalytic degradation and electrochemical activity of ZnO/CeO2 nanocomposite.

In this study, pure ZnO, CeO2 and ZnO/CeO2 nanocomposites were synthesized using a thermal decomposition method and subsequently characterized using different standard techniques. High-resolution X-ray photoelectron spectroscopy measurements confirmed the oxidation states and presence of Zn2+, Ce4+, Ce3+ and different bonded oxygen species in the nanocomposites. The prepared pure ZnO and CeO2 as well as the ZnO/CeO2 nanocomposites with various proportions of ZnO and CeO2 were tested for photocatalytic degradation of methyl orange, methylene blue and phenol under visible-light irradiation. The optimized and highly efficient ZnO/CeO2 (90:10) nanocomposite exhibited enhanced photocatalytic degradation performance for the degradation of methyl orange, methylene blue, and phenol as well as industrial textile effluent compared to ZnO, CeO2 and the other investigated nanocomposites. Moreover, the recycling results demonstrate that the ZnO/CeO2 (90:10) nanocomposite exhibited good stability and long-term durability. Furthermore, the prepared ZnO/CeO2 nanocomposites were used for the electrochemical detection of uric acid and ascorbic acid. The ZnO/CeO2 (90:10) nanocomposite also demonstrated the best detection, sensitivity and performance among the investigated materials in this application. These findings suggest that the synthesized ZnO/CeO2 (90:10) nanocomposite could be effectively used in various applications.

Electrochemical detection of uric acid via uricase-immobilized graphene oxide

Measurement of the uric acid level in the body can be improved by biosensing with respect to the accuracy, sensitivity and time consumption. This study has reported the immobilization of uricase onto graphene oxide (GO) and its function for electrochemical detection of uric acid. Through chemical modification of GO using 1-ethyl-3-(dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysulfosuccinimide (NHS) as cross-linking reagents, the enzyme activity of the immobilized uricase was much comparable to the free enzyme with 88% of the activity retained. The modified GO-uricase (GOU) was then subjected to electrocatalytic detection of uric acid (UA) via cyclic voltammetry (CV). For that reason, a glassy carbon electrode (GCE) was modified by adhering the GO along with the immobilized uricase to facilitate the redox reaction between the enzyme and the substrate. The modified GOU/GCE outperformed a bare electrode through the electrocatalytic activity with an amplified electrical signal for the detection of UA. The electrocatalytic response showed a linear dependence on the UA concentration ranging from 0.02 to 0.49 mM with a detection limit of 3.45 μM at 3σ/m. The resulting biosensor also exhibited a high selectivity towards UA in the presence of other interference as well as good reproducibility.

Synthesis of a three-layered SiO2@Au nanoparticle@polyaniline nanocomposite and its application in simultaneous electrochemical detection of uric acid and ascorbic acid.

Novel nanocomposites fabricated by incorporating different types of nanomaterials, especially inorganic and organic nanomaterials, have attracted much attention, and shown promising prospects in the applications in biological research fields. Herein, we propose a facile method to synthesize a novel three-layered SiO2@Au nanoparticle@polyaniline nanocomposite, which exhibited excellent electrical conductivity and good dispersibility in water. The as-proposed nanocomposite has been adopted to construct the modified electrode SiO2@AuNP@PANI/CS/GCE, which was characterized by electrochemical impedance spectroscopy and cyclic voltammetry, and demonstrated excellent electrochemical behaviors in neutral and even alkaline media, making it suitable for sensing species in biological fluids under physiological conditions. Moreover, the SiO2@AuNP@PANI/CS/GCE exhibited excellent catalytic activity towards the electro-oxidation of uric acid (UA) and ascorbic acid (AA), and a difference of 384 mV between the oxidation potentials for UA and AA was obtained, which is large enough for the selective and simultaneous determination of UA and AA in a binary mixture. Thus, the modified electrode has been successfully adopted for the simultaneous electrochemical detection of UA and AA, and the detection limits of 2 μM and 6 μM were obtained, respectively.

Electrochemical detection of uric acid using ruthenium-dioxide-coated carbon nanotube directly grown onto Si wafer

Carbon nanotubes (CNTs) directly grown onto a Si substrate by thermal chemical vapor deposition were used in uric acid (UA) detection. The process is simple and formation is easy without the need for additional chemical treatments. However, CNTs lack selectivity and sensitivity to UA. To enhance the electrochemical analysis, ruthenium oxide was used as a catalytic mediator in the modification of electrodes. The electrochemical results show that RuO2 nanostructures coated onto CNTs can strengthen the UA signal. The peak currents of RuO2 nanostructures coated onto CNTs linearly increase with increasing UA concentration, meaning that they can work as electrodes for UA detection. The lowest detection limit and highest sensitivity were 55 nM and 4.36 µA/µM, respectively. Moreover, the characteristics of RuO2 nanostructures coated onto CNTs were examined by scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy.

Electrochemical detection of uric acid and ascorbic acid: Application in serum

Abstract The detection and quantification of uric acid (UA) and ascorbic acid (AA) in different biological fluids such as serum is very important in clinical diagnosis. In this study, a sonogel–carbon electrode modified with l -cysteine was used for detection and quantification of these molecules by cyclic voltammetry (CV) and square wave voltammetry (SWV). These two methods are known for their suitability for monitoring of bioactive molecules in biological samples. Optimization of parameters affecting selectivity and sensitivity of these two methods is included. The peak current showed a linear relationship with the concentrations of UA and AA in the range of 10 − 5 M to 10 − 4 M for UA and 5 × 10 − 5 M respectively. The detection limit was of 10 − 5 M for UA and 5 × 10 − 5 M for AA. In addition, the interference of UA and AA was also studied. A neat separation of the oxidation peaks of these two compounds with a peak-to-peak separation of 295 mV was registered. The results indicate that carbon electrode modified with l -cysteine can successfully be used for a selective and sensitive simultaneous determination of UA and AA in the serum.

A Nicotinamide Adenine Dinucleotide Dispersed Multi-walled Carbon Nanotubes Electrode for Direct and Selective Electrochemical Detection of Uric Acid.

A nanocomposite platform built with multi-walled carbon nanotubes (MWCNTs) and nicotinamide adenine dinucleotide (NAD(+)) via a noncovalent interaction between the large π systems in NAD(+) molecules and MWCNTs on a glassy carbon substrate was successfully developed for the sensitive and selective detection of uric acid (UA) in the presence of ascorbic acid (AA), dopamine (DA). NAD(+) has an adenine subunit and a nicotinamide subunit, which enabled interaction with the purine subunit of UA through a strong π-π interaction to enhance the specificity of UA. Compared with a bare glassy carbon electrode (GCE) and MWCNTs/GCE, the MWCNTs-NAD(+)/GCE showed a low background current and a remarkable enhancement of the oxidation peak current of UA. Using differential pulse voltammetry (DPV), a high sensitivity for the determination of UA was explored for the MWCNTs-NAD(+) modified electrode. A linear relationship between the DPV peak current of UA and its concentration could be obtained in the range of 0.05 - 10 μM with the detection limit as low as 10 nM (S/N = 3). This present strategy provides a novel and promising platform for the detection of UA in human urine and serum samples.

Nitrogen-incorporated ultrananocrystalline diamond microneedle arrays for electrochemical biosensing

Microneedles are minimally invasive transdermal medical devices that are utilized for various applications, including drug delivery, fluid sampling, micro-dialysis, and electrochemical sensing. These devices are associated with less pain and tissue damage as compared with conventional hypodermic needle-based devices. In this study, we demonstrate fabrication of titanium alloy microneedle arrays with nitrogen-incorporated ultrananocrystalline diamond (N-UNCD) coatings. Microneedles were micromachined from ASTM F136 ELI Ti–6Al–4V alloy, a widely used medical-grade titanium alloy. N-UNCD coatings were deposited on the microneedles using microwave plasma enhanced chemical vapor deposition to enhance mechanical strength, increase hardness, improve biocompatibility, and provide an electrochemically stable surface. The structural and chemical properties of the N-UNCD titanium alloy microneedle arrays were evaluated using scanning electron microscopy and Raman spectroscopy. The mechanical robustness and skin penetration capability of the devices were demonstrated using cadaveric porcine skin. Finally, the electrochemical properties of the N-UNCD electrodes were evaluated; in vitro electrochemical detection of uric acid and dopamine was demonstrated using unmodified N-UNCD electrodes. These results demonstrate the application potential of N-UNCD-coated titanium alloy microneedles for transdermal electrochemical biosensing applications.

Controllable Growth of Conical and Cylindrical TiO2-Carbon Core-Shell Nanofiber Arrays and Morphologically Dependent Electrochemical Properties

Quasi-aligned cylindrical and conical core-shell nanofibers consisting of carbon shells and TiO(2) nanowire cores are produced in situ on Ti foils without using a foreign metallic catalyst and template. A cylindrical nanofiber has a TiO(2) nanowire core 30-50 nm in diameter and a 5-10 nm-thick cylindrical carbon shell, while in the conical nanostructure the TiO(2) nanowire core has a diameter of 20-40 nm and the thickness of the carbon shell varies from about 200 nm at the bottom to about 5 nm at the tip. Electrochemical analysis reveals well-defined redox peaks of the [Fe(CN)(6)](3-/4-) redox couple and heterogeneous charge-transfer rate constants of 0.010 and 0.062 cm s(-1) for the cylindrical and conical nanofibers, respectively. The coverage of exposed edge planes on the cylindrical and conical carbon shells is estimated to be 2.5 and 15.5 % respectively. The more abundant exposed edge planes on the conical nanofiber decrease the overpotential and increase the voltammetric resolution during electrochemical detection of uric acid and ascorbic acid. Our results suggest that the density of edge-plane sites estimated from Raman scattering is not necessarily equal to the density of exposed edge-plane sites, and only carbon electrodes with a large density of exposed edge planes or free graphene sheet ends exhibit better electrochemical performance.

Investigation of polyelectrolyte for electrochemical detection of uric acid in presence of ascorbic acid

Uric acid (UA) was detected in the presence of ascorbic acid (AA) at GC electrode by cyclic voltametry (CV) and differential pulse voltametry (DPV) in aqueous media of cationic polyelectrolyte (poly(diallyldimethylammonium chloride) (PDDA)). Both, UA and AA are anionic nature and electro-static attraction with cationic solution. This lowered their oxidation potentials and increased anodic current. In CV studies, the UA oxidation potential was decreased by 400mV in the presence of PDDA along with increase in peak current. Effect of PDDA and pH on Epa and Ipa were also studied. About 360mV difference in oxidation peak potentials was observed for AA and UA in PDDA media, which established a quick method for their simultaneous determination. The detection limit of UA in the presence of 200 folds AA was found as 1μM with correlation coefficient of 0.994 and sensitivity of 0.05μAμM−1. The proposed method has been also applied for determining the UA in human urine without any pretreatment, and found to be satisfactory.

Simultaneous electrochemical detection of uric acid and ascorbic acid at a silver doped poly(glutamic acid) modified glassy carbon electrode

In this paper, the silver doped poly (L-glutamic acid) modified glassy carbon electrode (PLG-Ag/GCE) was fabricated through an electrochemical immobilization. The modified electrode was used for simultaneous determination of uric acid (UA) and ascorbic acid (AA) in 0.1 M phosphate buffer solutions (PBS). The cyclic voltammetric signals of UA and AA were well separated with a potential difference of 396 mV in pH 3.0 phosphate buffer solution. The linear calibration curves were obtained in the concentration range 5.00 × 10−7–1.00 × 10−4 M for UA and 8.00 × 10-6–5.00 × 10−3 M for AA with the detection limits of 3 × 10−7 M and 4 × 10−6 M, respectively. The relative standard deviations were 1.3 and 1.0% for the determinations of UA and AA for 20 continuous measurements. The signal was highly stable and reproducible. This method was successfully applied to the determination of UA in human urine samples.

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

AbstractThe present review has sought to explore the technological advances that have been made in recent years towards the selective analysis of uric acid and critically evaluate how they could, in fact, be exploited as a basis for a multi analyte sensor incorporating uric acid detection. Numerous strategies have evolved in recent years but these have invariably focused on the manufacture and response characterization of discrete sensors. Various methods of obtaining selective detection such as use of uricase enzymes, nanoparticles, carbon nanotubes, polymers, conducting polymers and MIPs are also discussed along with the clinical relevance of UA determination.

Sulfur-adlayer-coated gold electrode for the in vitro electrochemical detection of uric acid in urine

The present article demonstrates the electrochemical oxidation of uric acid (UA) at sulfur-adlayer-coated gold (S-Au) electrode in alkaline media. At S-Au electrode, UA oxidized at a significantly lower overpotential with a higher current density as compared to the bare Au electrode. The oxidation of UA at the S-Au electrode is highly selective in the presence of the other commonly existing bio-molecules in urine. The proposed electrochemical sensor not only exhibited good reproducibility, but also showed a fast amperometric response to UA in the concentration range of 0.0025–5 mM with a low detection limit of 0.4 μM.

Simultaneous electrochemical detection of uric acid and ascorbic acid at a poly( N, N-dimethylaniline) film-coated GC electrode

A polymer film of N, N-dimethylaniline (PDMA) having a positive charge on the quarternary ammonium group in its backbone was electrochemically deposited on a glassy carbon (GC) electrode surface. The resulting film-coated GC electrode was used to detect uric acid (UA) electrochemically in the presence of ascorbic acid (AA). Both UA and AA are anionic in a solution of pH 7 and thus were attracted to the film, which lowered their oxidation potentials and increased their oxidation currents. In cyclic voltammetric measurements, the negative shift of the oxidation potential of UA (by 0.28 V) compared with that at the bare electrode was larger than that of AA (by 0.2 V). Also the increase in the oxidation current of UA at the PDMA film-coated electrode was larger than that of AA. In square wave voltammetric measurements, the PDMA film-coated electrode could separate the oxidation peak potentials of UA and AA present in the same solution by about 200 mV though the bare electrode gave a single broad response. A successful elimination of the fouling effect by the oxidized product of AA on the response of UA has been achieved at the PDMA film-coated electrode. The detection limit of UA in the presence of 160-fold excess of AA was found as 1.25 μM and the current response for UA increased linearly with increase of its concentration from 1.25 to 68.75 μM in the presence of AA with a correlation coefficient of 0.999 and a sensitivity of 0.0276 μA μM −1. In flow injection analysis, a good linear relationship between the oxidation current and the concentration from 2 to 21 μM of UA was found. The sensitivity of the PDMA film-coated electrode towards UA was calculated as 0.0285 μA μM −1 with a correlation coefficient of 0.997. The stable and reproducible response for both AA and UA at the PDMA film-coated electrode was verified by flow injection experiments. As the response of UA was reproducible in the presence of AA, it was expected that the oxidized product of AA would not affect the electrode response of UA. Moreover, the physiologically common interferents (i.e., glucose, purine, urea and citrate) negligibly affected the response of UA. The PDMA film-coated electrode exhibited a stable and sensitive response to UA in the presence of interferents.

Changes in xanthine oxidase in ischemic rat brain

Xanthine oxidase activity in the rat brain was measured by means of high-performance liquid chromatography with electrochemical detection of uric acid. Cerebral ischemia was produced by a four-vessel occlusion method. In the control rat, the enzyme activity was 0.87 +/- 0.13 nmol/gm wet weight/min at 25 degrees C (mean +/- standard deviation), of which 92.4% was associated with the nicotinamide adenine dinucleotide (NAD)-dependent dehydrogenase form and only 7.6% with the oxygen-dependent superoxide-producing oxidase form. However, the ratio of the latter form increased to 43.7% after 30 minutes of global ischemia, despite the total xanthine oxidase activity remaining the same. Thus, it was revealed that uric acid can be synthesized in the rat brain and that cerebral ischemia induced the conversion of xanthine oxidase from an NAD-dependent dehydrogenase to an oxygen-dependent superoxide-producing oxidase. Although the xanthine oxidase pathway has been proposed as a source of oxygen-derived free radicals in various ischemic organs other than brain, the results of the present study suggest the involvement of the oxygen free radicals generated from this pathway in the pathogenesis of the ischemic injury of the rat brain.