Colorimetric Detection of Uric Acid with High Sensitivity Using Cu2O@Ag Nanocomposites

Gold nanostructures on polyelectrolyte-brush-modified cellulose membranes as a synergistic platform for uric acid detection

In this study, we present a convenient approach utilizing gold nanostructures coated cellulose membrane for the quantification of uric acid in an aqueous solution. The synthesis of system was achieved by functionalizing cellulose membrane with poly[2-(methacryloyloxy)ethyl]trimethylammonium chloride (PMETAC) and cross-linked with ethylene glycol dimethacrylate (EGDMA). FT-IR and XPS confirm the formation of PMETAC and PMETAC/EGDMA on the cellulose. The fabricated substrates were exposed to tetrachloroaurate solution, then reduced by NaBH4. We have systematically investigated the catalytic oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by hydrogen peroxide (H2O2) in various pH conditions, absent uric acid, using the fabricated substrates. The colorimetric response-observed through UV-Vis spectroscopy-revealed significant shifts in absorbance at 660 nm, correlating with uric acid concentrations across a range of pH levels. The films exhibited a pronounced color change from green to light yellow in basic to neutral environments and from yellow to dark green under more acidic conditions, demonstrating their potential for high-sensitivity uric acid detection. The assessment of the catalytic films' reusability and stability revealed insights into their enduring performance, identifying opportunities for enhancing material design and functionality for extended applications. This study not only underscores the films' versatile detection capabilities but also emphasizes the importance of pH in tuning the assay's sensitivity and specificity.

Colorimetric and electrochemical dual-mode uric acid determination utilizing peroxidase-mimicking activity of CoCu bimetallic nanoclusters

We present the preparation of CoCu bimetallic nanoclusters (Co@Cu-BNCs) by a hydrothermal and one-step pyrolysis method to build a colorimetric and electrochemical dual-mode sensing platform for uric acid (UA) detection. In the presence of H2O2, Co@Cu-BNCs with peroxidase-mimicking activity may convert colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue-colored oxidized TMB (oxTMB). However, due to the inhibitory effect of uric acid (UA) on the oxidation process of TMB, the characteristic absorption peak intensity of oxTMB decreased when UA was added into a mixed solution. In this approach, a colorimetric assay platform for the detection of UA was demonstrated, with a linear range of 0.1-195 μM and a low limit of detection of 0.06 μM (S/N ratio of 3). In addition, an even wider detection range is achieved in the electrochemical method, due to the pronounced electrocatalytic activity of Co@Cu-BNCs. The surface of the glassy carbon electrode was modified with Co@Cu-BNCs to build an electrochemical sensor for detecting UA. The sensor achieves a wider linear range from 2 to 1000 μM and a limit of detection of 0.61 μM (S/N ratio of 3). Moreover, the detection of UA in a human serum sample showed satisfactory results. The results proved that the colorimetric and electrochemical dual-mode detection platform was sensitive, convenient and accurate.

A new spectrophotometric method for uric acid detection based on copper doped mimic peroxidase

Cascade reactions catalyzed by natural uricase and mimic peroxidase (MPOD) have been applied for uric acid (UA) detection. However, the optimal catalytic activity of MPOD is mostly in acidic conditions (pH 2-5), mismatching the optimal catalytic alkaline environment of uricase. In this paper, using CuSO₄ and urea as raw materials, a MPOD with high catalytic activity in alkaline environment was synthesized by hydrothermal method. Then, based on coupling reaction of uricase/UA/MPOD/guaiacol (GA) system, a novel spectrophotometric method was established to detect 5-60 μmol/L UA (limit of detection = 3.14 μmol/L (S/N = 3)) and accurately quantified serum UA (275.6 ± 39.9 μmol/L, n = 5) with 95-105% of standard addition recovery. The results were consistent with commercial UA kit (p > 0.05). The MPOD could replace natural POD to reduce the cost of UA detection due to simple preparation and cheap raw materials, and is expected to achieve the specific detection of some substances, like glucose and cholesterol, combined with glucose oxidase and cholesterol oxidase.

Developing Activated Carbon Veil Electrode for Sensing Salivary Uric Acid

The paper describes the development of a carbon veil-based electrode (CVE) for determining uric acid (UA) in saliva. The electrode was manufactured by lamination technology, electrochemically activated and used as a highly sensitive voltammetric sensor (CVEact). Potentiostatic polarization of the electrode at 2.0 V in H2SO4 solution resulted in a higher number of oxygen and nitrogen-containing groups on the electrode surface; lower charge transfer resistance; a 1.5 times increase in the effective surface area and a decrease in the UA oxidation potential by over 0.4 V, compared with the non-activated CVE, which was confirmed by energy dispersive X-ray spectroscopy, electrochemical impedance spectroscopy, chronoamperometry and linear sweep voltammetry. The developed sensor is characterized by a low detection limit of 0.05 µM and a wide linear range (0.09-700 µM). The results suggest that the sensor has perspective applications for quick determination of UA in artificial and human saliva. RSD does not exceed 3.9%, and recovery is 96-105%. UA makes a significant contribution to the antioxidant activity (AOA) of saliva (≈60%). In addition to its high analytical characteristics, the important advantages of the proposed CVEact are the simple, scalable, and cost-effective manufacturing technology and the absence of additional complex and time-consuming modification operations.