Oxidation Of Uric Acid Research Articles

Simultaneous Electrochemical Detection of Dopamine and Uric Acid via Au@Cu-Metal Organic Framework.

The incorporation of noble metals with metal-organic frameworks (MOFs) are conducive to the simultaneous electrochemical detection of analytes owing to multiple accessible reaction sites. Herein, Au@Cu-metal organic framework (Au@Cu-MOF) is successfully synthesized and modified as a screen-printed carbon electrode (SPCE), which serves as an excellent electrocatalyst for the oxidation of dopamine (DA) and uric acid (UA). The sensor shows a linear range from 10 μM to 1000 μM, with sensitivity and detection limit of 0.231 μA μM-1 cm-2 and 3.40 μM for DA, and 0.275 μA μM-1 cm-2 and 10.36 μM for UA. Au@Cu-MOF could realize the individual and simultaneous electrochemical sensing of DA and UA, with distinguishable oxidation peak potentials. Moreover, it exhibits reproducibility, repeatability, and stability. Ultimately, the sensor provides an avenue for an ultrasensitive label-free electrochemical detection of DA and UA.

2-D graphitic carbon nitride fabricated electrode as a robust inexpensive electrochemical scaffold for the real-time detection of serum uric acid in gout patients

Graphitic carbon nitride (g-C3N4) modified screen printed carbon (SPC) electrodes were found to be an excellent probe for the real-time quantification of serum uric acid (UA) in gouty patients upon performing exercises of different regime. Nitrogen-rich precursor like melamine was used for the preparation of g-C3N4 via thermal polycondensation. The prepared materials were well characterized using various spectroscopic and microscopic techniques. The as-prepared g-C3N4 was electrochemically deposited on SPC electrode for the effective determination of serum UA at physiological pH. Since the current response generated from serum UA and commercial UA was different, the calibration of the modified electrode was carried out by using serum UA. The UA oxidation current was increased linearly from 5 to 40 µM with a correlation coefficient of 0.9948 at g-C3N4/SPC electrode. Several volunteers were subjected to the quantification of serum UA and among them gouty patients were selected and subjected to various exercises like Mild, RAST and Yoga. Periodically the serum UA was collected and analysed via the modified electrode as well as with the standard method. It was found that the serum UA content increases upon performing exercises and it was concluded that exercises cannot reduces the serum UA. The results obtained from the present electrochemical sensor were highly consistent with the results of clinical methods upon validation, which authenticates the practicability of the fabricated sensor in real-time applications.

Salivary and Serum Levels of Both Uric Acid and C-Reactive Protein (CRP) Biomarkers in Patients with Behçet's Disease

Behçet's disease (BD) is a systemic vasculitis identified by recurrent oral and genital ulcerations, skin inflammations and uveitis, with unknown etiology. This study had been designed to assess the level of salivary and serum uric acid (UA) and C - reactive protein (CRP) markers in BD patients as activity markers and to explore their relations in disease existence. Fifty BD patients :( 32 males and 18 females) with mean age (35.3 ± 7.6) years and fifty healthy subjects (30 males and 20 females) with mean age (34.8± 9.1) years were involved in this study that extend during the period of (2014-2016). All of patients and healthy subjects were analyzed for UA by (colorimetric spectrophotometric assay that based on oxidation of UA by uricase enzyme to allantoin) and CRP by (qualitative analysis: antigen-antibody interaction Latex agglutination test) in both saliva and serum. Data was analyzed using descriptive statistics, t-test, P (ANOVA) test, Chi-square (2) test, and Pearson’s linear correlation coefficient statistical analyses. Results of this study show that salivary uric acid was significantly elevated in BD patients than in healthy subjects. (P<0.001). Although serum UA was higher in patients than the healthy subjects but statistically not significant. (P=0.57). On the other hand, out of fifty patients there were thirteen patients (26%) significantly expressed CRP positive in their serum and saliva. The results of this study revealed that UA can act as prooxidant (pro inflammatory) marker and CRP as inflammatory marker that could be related to impaired endothelial function in BD.

Synthesis of cobalt phosphide hybrid for simultaneous electrochemical detection of ascorbic acid, dopamine, and uric acid.

Ascorbic acid (AA), dopamine (DA), and uric acid (UA) are important biomarkers for the clinical screening of diseases. However, the simultaneous determination of these three analytes is still challenging. Herein, we report a facile metal-organic framework (MOF)-derived method to synthesize a cobalt phosphide (Co2P) hybrid for the simultaneous electrochemical detection of AA, DA and UA. The introduction of highly dispersed Co2P nanoparticles onto a P, N-doped porous carbon matrix is responsible for providing abundant active sites and facilitating electron transfer, thereby contributing to the improved electrocatalytic performance of the hybrid. Well-resolved oxidation peaks and an enhanced current response for the simultaneous oxidation of AA, DA, and UA were achieved using a Co2P hybrid-modified screen-printed electrode (Co2P hybrid-SPE) with the differential pulse voltammetry (DPV) method. The detection limits for AA, DA, and UA in simultaneous detection were calculated as 17.80 μM, 0.018 μM, and 0.068 μM (S/N = 3), respectively. Furthermore, the feasibility of using Co2P hybrid-SPE for the simultaneous detection of AA, DA, and UA in real serum samples was also confirmed.

A surface modified laser-induced graphene based flexible biosensor for multiplexed sweat analysis.

The growing popularity of electrochemical sensors featuring non-invasive biosensing technologies has generated significant enthusiasm for continuous monitoring of bodily fluid biomarkers, potentially aiding in the early detection of health issues in individuals. However, detection of multiple biomarkers in complex biofluids often necessitates a high-density array which creates a challenge in achieving cost-effective fabrication methods. To overcome this constraint, this work reports the fabrication of an electrochemical sensor utilizing a NiO-Ti3C2Tx MXene-modified flexible laser-induced graphene (LIG) electrode for the separate and concurrent analysis of ascorbic acid (AA), dopamine (DA), and uric acid (UA) in human sweat and also addresses the deficiencies in the existing state of the art by offering a cost-efficient and high-performance sensor that mitigates the degrading constraints of conventional LIG electrodes. Cyclic voltammetry and differential pulse voltammetry measurements reveals that the electrochemical properties of the modified electrode, attain a low detection limit and great sensitivity for the target biomarkers. The NiO-Ti3C2Tx/LIG sensor demonstrated enhanced electrocatalytic activity for the oxidation of ascorbic acid, dopamine, and uric acid, and proved useful for analysing these biomarkers in synthetic sweat samples. Under the optimized conditions, the LOD values were estimated to be 16, 1.97 and 0.78 μM for AA, DA and UA, respectively. The developed high-efficiency sensor holds significant promise for applications in flexible and wearable electronics for health monitoring.

Efficient and fast detection of uric acid based on a colorimetric sensing method.

The uric acid (UA) level is an important physiological indicator of the human body, and its abnormality can lead to a series of diseases. Therefore, the immediate detection of uric acid concentration has broad application prospects. Commonly used methods for the analysis of uric acid include chromatography, high-performance capillary electrophoresis and electrochemical methods. However, these methods have the disadvantages of cumbersome sample pre-treatment, high cost, time-consuming, and the need for experimental instruments and professional operators, which are extremely unfavorable for the detection of uric acid and the diagnosis of related diseases in resource-limited areas. In this study, a portable visualization method was developed for the detection of uric acid using hydrogen peroxide (H2O2) test strips. Uric acid enzyme specifically catalyzes the oxidation of uric acid to produce H2O2, which causes a significant change in the color of the H2O2 test strip. The response has good linearity in the range of 1 ∼ 50 μg mL-1. Thus, it provides a simple, rapid, and cost-effective visualized bioassay for uric acid.

LC/MS/MS detection of uric acid oxidation metabolites to evaluate reactive oxygen and nitrogen species <i>in vivo</i> with application to pseudo-inflammation

LC/MS/MS detection of uric acid oxidation metabolites to evaluate reactive oxygen and nitrogen species <i>in vivo</i> with application to pseudo-inflammation

5-N-Carboxyimino-6-aminopyrimidine-2,4(3H)-dione, a novel indicator for hypochlorite formation.

Uric acid is an adequate and endogenous probe for identifying reactive oxygen or nitrogen species generated in vivo because its oxidation products are specific to reacted reactive oxygen or nitrogen species. Recently, we identified 5-N-carboxyimino-6-N-chloroaminopyrimidine-2,4(3H)-dione as a hypochlorite-specific oxidation product. 5-N-carboxyimino-6-N-chloroaminopyrimidine-2,4(3H)-dione was anticipated to be a biomarker for hypochlorite production in vivo. However, while it was stable in aqueous solution at weak acidic and alkaline pH (6.0-8.0), it was unstable in human plasma. In this study, we found that 5-N-carboxyimino-6-N-chloroaminopyrimidine-2,4(3H)-dione rapidly reacted with thiol compounds such as cysteine and glutathione to yield 5-N-carboxyimino-6-aminopyrimidine-2,4(3H)-dione, which was stable in human plasma unlike 5-N-carboxyimino-6-N-chloroaminopyrimidine-2,4(3H)-dione. 5-N-carboxyimino-6-aminopyrimidine-2,4(3H)-dione was produced upon uric acid degradation during myeloperoxidase-induced uric acid oxidation and lipopolysaccharide-induced pseudo-inflammation in collected 2,4(3H)-dione has potential as a marker for hypochlorite production in vivo.

Cost-effective quantification of uric acid using niobium oxide and graphene oxide-modified pencil-drawn electrodes on PVC substrates.

This study introduces a cost-effective approach for quantifying uric acid (UA), the main antioxidant species in human physiology and implicated in inflammatory regulation. Using a PVC substrate and pencil drawing technique, electrodes were fabricated and modified with niobium oxide and graphene oxide via a straightforward "drop casting" method. The nanostructures of the substrate, electrode, and modified electrode were evaluated using SEM images. The synergistic effect between these materials significantly facilitated the uric acid oxidation process with a 400 mV peak potential shift and 45% current increase. The evaluation of the electrode's response to common blood and urine components showed minimal deviation. Among the components tested-ascorbic acid, glucose, nitrate, nitrite, cysteine, urea, creatinine, and ammonium ion-only the ammonium ion exhibited a 10% interference at concentrations commonly found in urine. The sensors showed a good detection limit of 8.7 μmol L-1, with a wide linear range from 8.7 to 2000 μmol L-1 with a correlation factor of 0.9993 for five different sensors. The reproducibility and repeatability of the produced sensors were estimated by the RSD at 4% and 1%, respectively. Synthetic urine samples spiked exhibited reliable analysis, with recovery values within a 5% error margin. This work presents a practical, simple, and affordable sensor platform for rapid and accurate UA quantification.

Amine-Functionalized Pencil Graphite Electrode for Simultaneous Determination of Dopamine and Uric Acid

In this study, an electrochemical transducer based on an Amine-functionalized cheap and disposable pencil graphite electrode (NPGE) is proposed for the simultaneous monitoring of Dopamine (DA) and Uric Acid (UA) in biological samples such as serum and urine. The prepared NPGE was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). It was found that the incorporation of amine groups significantly improved catalytic activity than the bare pencil graphite electrode (BPGE). Moreover, the electrode modification parameters and effects of different analytical variables such as sweep rate, pH of the supporting electrolyte solution, and possible interfering ions or molecules in quantification were optimized using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under optimized conditions, DA and UA oxidation currents showed linear responses over the concentration range of 1.06-160 µM for DA and 30.06-150 µM for UA. The limit of detection (LOD) for DA and UA were estimated to be 0.94 and 1.26 µM, respectively. In addition, the transducer’s sensitivity of 5.47 µA.µM-1cm-2 for DA and 1.70 µA.µM-1cm-2 for UA were calculated. Aiming to reuse the transducer, a regeneration solution is proposed which could successfully remove the adsorbed oxidized products from the surface. Finally, the developed transducer’s performance was compared with the established clinical method. Figure 1

Enhancing uric acid electrochemical detection with copper ion-activated mini protein mimicking uricase within ZIF-8: response surface methodology (RSM) optimization.

This study aims to investigate the influence of copper(II) ions as a cofactor on the electrochemical performance of a biocomposite consisting of a mini protein mimicking uricase (mp20) and zeolitic immidazolate framework-8 (ZIF-8) for the detection of uric acid. A central composite design (CCD) was utilized to optimize the independent investigation, including pH, deposition potential, and deposition time, while the current response resulting from the electrocatalytic oxidation of uric acid was used as the response. The statistical analysis of variance (ANOVA) showed a good correlation between the experimental and predicted data, with a residual standard error percentage (RSE%) of less than 2% for predicting optimal conditions. The synergistic effect of the nanoporous ZIF-8 host, Cu(II)-activated mp20, and reduced graphene oxide (rGO) layer resulted in a highly sensitive biosensor with a limit of detection (LOD) of 0.21 μM and a reproducibility of the response (RSD = 0.63%). The Cu(II)-activated mp20@ZIF-8/rGO/SPCE was highly selective in the presence of common interferents, and the fabricated layer exhibited remarkable stability with signal changes below 4.15% after 60 days. The biosensor's reliable performance was confirmed through real sample analyses of human serum and urine, with comparable recovery values to conventional HPLC.

Uric Acid Oxidation Products Correlate with Sepsis and Promote Modification on Serum Albumin in Intensive Care Unit Patients

Uric Acid Oxidation Products Correlate with Sepsis and Promote Modification on Serum Albumin in Intensive Care Unit Patients

Flexible piezo-electrocatalytic uric acid sensor

Non-invasive longitudinal monitoring of uric acid (UA) levels in human sweat could enable unprecedented diagnosis, therapy, and prognosis of numerous physiological and psychological conditions with societal and economic impacts. However, state-of-the-art flexible UA sensors are limited by their complicated fabrication processes, sophisticated instruments, expensive raw materials, and unsatisfactory detection performance. In this study, we designed and implemented for the first time a flexible piezo-electrocatalytic uric acid sensor (EPICS) based on ZnO nanorods. We demonstrated that the EPICS devices achieve a 4-fold enhancement in the UA sensing performance with a small compressive strain (−0.9%), boosted by piezo-electrocatalysis during the electrochemical oxidation of UA on the surfaces of mechanically deformed ZnO nanorods. The EPICS devices exhibited a superior sensitivity of 3.91 µA µM−1 cm−2 and a limit of detection of 0.086 µM, outperforming all reported flexible electrochemical UA sensors. Our design allows the possibility of non-invasive monitoring of UA with a boosted performance by otherwise wasted mechanical energy, such as that from the human body. The fundamental piezo-electrocatalytic principles can also be extended to other piezoelectric materials with catalytic properties for high-performance sensing in the biomedical, pharmaceutical, and agricultural areas.

Electrochemical sensor using cobalt oxide-modified porous carbon for uric acid determination.

An electrochemical sensor for the detection of uric acid was constructed using cobalt oxide-modified porous carbon@multi-walled carbon nanotube (MWCNTs) composite material for the modification of theelectrode. Firstly, ZIF-67 is generated on carbon nanotubes using thesurfactant cetylammonium bromide (CTAB) as template. The vesicles generated by CTAB act as nucleation sites for the in situ growth of ZIF-67. Then, cobalt oxide-modified porous carbon was obtained after high-temperature carbonization of ZIF-67, leading to the formation of cobalt oxide-modified porous carbon@MWCNT composite materials. Co-N and Co-O active sites on the composite material can improve the oxidation of uric acid on the electrode surface, leading to enhanced sensitivity and selectivity for uric acid detection. The sensor has a good linear range from 1 to 40 μM for uric acid detection with a detection limit of 0.09 μM. The sensor was utilized for determination of uric acid in actual serum samples.

Sonoelectrochemical nitrided graphene nanosheets with vacancies and their applications for catalysis and sensing of uric acid oxidation

A sonoelectrochemical method for preparing N-doped defective graphene nanosheets (N/O-dGNs) with point defects and 5-9 or 5-8-5 vacancies and oxygen-containing groups was successfully demonstrated. In this one-pot approach, the N-bonding configuration and N content of N/O-dGNs were finely tuned by the ultrasonic power (192, 320, and 640 W). The N content in atomic percentage (at%) for N/O-dGN (N/O-dGN320W) with point defects and 5-8-5 vacancy prepared at 320 W power was 5.6 at%, greater than 3.0 at% and 2.6 at% for N/O-dGN with point defects and 5-9 vacancies at 192 W and 640 W power (N/O-dGN192W and N/O-dGN640W), respectively. N-bonding sites on N/O-dGN320W were dominantly amine N (2.1 at%) and pyrrolic N (2.4 at%). Additionally, the electrocatalytic activity of N/O-dGN192W, N/O-dGN320W, and N/O-dGN640W was successfully demonstrated for the sequential uric acid (UA) oxidation reaction (UOR), in which N/O-dGN320W displayed a significant mass activity (2.51 A/g). As in the transient catalysis of UOR, N/O-dGN320W with amine N showed 400.8 μA mM−1 cm−2 in sensitivity within a wide linear analysis range (1.5 × 10–2–6 mM) for amperometrically sensing UA. The results of real sample experiments using serum samples further demonstrated the potential of N/O-dGN320W as a non-enzymatic UA sensor.

Preparation of PEGylated uricase attached magnetic nanowires and application for uric acid oxidation.

The present study aims to immobilize the uricase enzyme on magnetic nanowires and to examine its potential for use in the treatment of gout. For this, Au/Ni/Au nanowires were synthesized using a polycarbonate membrane template by the sequential electrodeposition of Au, Ni, and Au, respectively. The uricase enzyme was covalently attached to these nanowires and was also coated with PEG. Optimum enzymatic conditions, kinetic parameters, thermal, storage, and operational stability were determined by performing enzymatic activity tests of free and immobilized uricase. Additionally, the efficacy of both enzyme preparations in artificial human serum and the presence of protease was also investigated. Experimental results showed that immobilized uricase showed higher stability than free uricase in all studied conditions. The potential of immobilized uricase to oxidize uric acid in artificial serum was also investigated and it was found that immobilized preparation demonstrated approximately 6 times higher activity than that of the free enzyme. The results of this study showed that uricase-attached nanowires oxidized uric acid effectively and are promising in the treatment of gout.

Cascade enzymatic preparation of carboxymethyl chitosan-based multifunctional hydrogels for promoting cutaneous wound healing

Designing wound dressings with inherent multifunctional therapeutic effects is desirable for clinical applications. Herein, a series of multifunctional carboxymethyl chitosan (CMCS)-based hydrogels were fabricated by the facile urate oxidase (UOX)-horseradish peroxidase (HRP) cascade enzymatic crosslinking system. For the first time, the cascade enzymatic crosslinking system was not only used for preparing hydrogel wound dressings but also for accelerating wound healing due to the activity retention of the self-compartmental enzymes. A CMCS derivative (HCMCS-mF) synthesized by successively grafting 4-hydroxybenzaldehyde (H) and 5-methylfurfural (mF) on CMCS and a quaternary ammonium crosslinker (QMal) with terminal grafting maleimide (Mal) groups were combined with enzymatic system for the facile preparation of hydrogels. The mild Diels-Alder (DA) crosslinking reaction between mF and Mal groups constructed the first network of hydrogels. The cascade UOX-HRP system mediated the oxidative crosslinking of phenols thus forming the second gel network. Self-entrapped UOX maintained its enzymatic activity and could continuously catalyze the oxidation of uric acid, generating therapeutic allantoin. These porous, degradable, mechanically stable hydrogels with excellent antioxidant performance and enhanced antibacterial capacity could effectively accelerate skin wound repair by simultaneously reducing oxidative stress, relieving inflammation, promoting collagen deposition and upregulating the expression level of CD31.

Optimum pH Buffer of Phosphate and Carbonate on The Crude Extraction of Uricase Enzyme from Goat Liver

Uricase enzyme (urate oxidase) is an enzyme that catalyze the oxidation of uric acid in the presence of oxygen to produce allantoin, carbon dioxide (CO2) and hydrogen peroxide (H2O2). Human and primates do not have this enzyme while other mammals have it in the liver therefore the uricase enzymes are extracted from goat liver use a buffer that is compatible with the human buffer system. The type of buffer selected adjusted at the appropriate pH. The optimum uricase pH ranged from 7.5 to 9.5. The selection of buffer type is adjusted to the human buffer system. The purpose of the study was to determine the effect of the type and pH of the extraction buffer on the total activity, protein total and specific activity of crude uricase. The types of buffer selected are phosphate buffer and carbonate buffer, while the selected pH is 7.5; 8.5; and 9.5. The method used is enzyme extraction, then determination of enzyme activity and protein content to determine the specific activity of the enzyme. The results obtained the highest total enzyme activity at pH 8.5 both in carbonate buffer (0.0481 U/mL) and phosphate buffer (0.0383 U/mL). The highest protein total in carbonate buffer was at pH 9.5 (4.55 mg/mL) while the highest value was in phosphate buffer pH 8.5 (4.1 mg/mL). The specific activity of uricase pH 8.5 was carbonate buffer (0.0114 U/mg) and phosphate buffer (0.0094 U/mg). The highest uricase specific activity value was at pH 8.5 for both carbonate and phosphate buffer types and in the long term it is used as a gout therapy.

Defective Prussian Blue Analogue with Cobalt for Fabrication of An Electrochemical Sensor for Detecting Ascorbic Acid, Dopamine and Uric Acid

AbstractA Prussian blue analogue with cobalt (Na2‐xCo[Fe(CN)6]1‐y, PB‐Co), which is often used as sodium‐ion battery material, was found to be an excellent sensing material toward some biomolecules by calcination. PB‐Co calcined at 750 °C for 1 h (PB‐Co750‐1) has the improved defects to facilitate the adsorption and the catalytic oxidation of ascorbic acid (AA), dopamine (DA) and uric acid (UA). PB‐Co750‐1 modified on screen printed carbon electrode (SPE) for the ultrasensitively simultaneous determination of AA, DA and UA demonstrates the wide linear range, the low limit of detection (LOD) and the good reproducibility. In addition, the redox of the analytes was confirmed as the diffusion‐controlled process via the kinetic study. The recoveries of AA, DA and UA in real samples were found between 91 % to 114 %. AA and UA in tablets, serums and urines could be determined by PB‐Co750‐1/SPE with the satisfactory results.

Simultaneous and Ratiometric Electrochemical Determination of Uric Acid and Hypoxanthine Based on In Situ Carbonized Polydopamine Graphene Paper

High levels of uric acid (UA) and xanthine (XA) in the human body can lead to various illnesses, highlighting the crucial need to detect UA and XA levels in the body. In this work, a ratiometric electrochemical detection platform was constructed for the simultaneous determination of UA and XA. Polydopamine (PDA) was initially modified in situ on graphene paper (Gp) and carbonized to fabricate the cPDA-Gp electrode. Methylene blue (MB) is coupled to cPDA-Gp as an internal reference and is designated as MB/cPDA-Gp. The electrochemical behavior of UA and XA on MB/cPDA-Gp was studied by cyclic voltammetry and differential pulse voltammetry. There were distinct anodic peaks on the electrode that corresponded to the oxidation of UA and XA in the concentration ranges of 0.6–350 and 2–160 μM, with detection limits of 0.2 and 0.67 μM, respectively (S/N = 3). For simultaneous detection of changes in UA and XA concentrations, the response range was 1–300 μM, with detection limits of 0.34 and 0.67 μM (S/N = 3), respectively. The sensing platform has been successfully utilized to detect UA and XA in real samples with satisfactory results, indicating that it can be a reliable sensor for detecting these analytes.