Sensitivity Detection of Uric Acid and Creatinine in Human Urine Based on Nanoporous Gold

Abstract

Given the significance of uric acid and creatinine in clinical diagnostic, disease prevention and treatment, a multifunctional electrochemical sensor was proposed for sensitive detection of uric acid and creatinine. The sensitive detection of uric acid was realized based on the unique electrochemical oxidation of nanoporous gold (NPG) towards uric acid, showing good linearity from 10 μM to 750 μM with a satisfactory sensitivity of 222.91 μA mM^-1 cm^-2 and a limit of detection (LOD) of 0.06 μM. Based on the Jaffé reaction between creatinine and picric acid, the sensitive detection of creatinine was indirectly achieved in a range from 10 to 2000 μM by determining the consumption of picric acid in the Jaffé reaction with a detection sensitivity of 195.05 μA mM^-1 cm^-2 and a LOD of 10 μM. For human urine detection using the proposed electrochemical sensor, the uric acid detection results were comparable to that of high-performance liquid chromatography (HPLC), with a deviation rate of less than 10.28% and the recoveries of uric acid spiked in urine samples were 89~118%. Compared with HPLC results, the deviation rate of creatinine detection in urine samples was less than 4.17% and the recoveries of creatinine spiked in urine samples ranged from 92.50% to 117.40%. The multifunctional electrochemical sensor exhibited many advantages in practical applications, including short detection time, high stability, simple operation, strong anti-interference ability, cost-effectiveness, and easy fabrication, which provided a promising alternative for urine analysis in clinical diagnosis.

Keywords: co-catalytic strategy; creatinine; human urine; nanoporous gold; uric acid.

Figure 1

(A) The SEM image of NPG at a magnification of 100,000×. (B) The CV curves of bare GCE and NPG/GCE in PBS (50 mM, pH 7.0). (C) The EIS profiles of bare GCE and NPG/GCE in 5.0 mM K₃Fe(CN)₆ solution (frequency range of 0.01 to 106 Hz). (D) The CV curves of bare GCE and NPG/GCE in 5.0 mM K₃Fe(CN)₆ solution.

Figure 2

(A) Schematic diagram for the construction of NPG/GCE (a) and catalytic oxidation of uric acid by the NPG/GCE (b). (B) The CV curves of NPG/GCE in PBS (50 mM, pH 7.0) with and without 1.0 mM uric acid a scan rate of 50 mV s⁻¹.

Figure 3

(A) The CV curves of the NPG/GCE in PBS (50 mM, pH 6.0) containing 1.0 mM uric acid at different scan rates. (B) The linear relationship between the oxidation peak current density of uric acid and the square root of scan rate for the electrooxidation of 1.0 mM uric acid. (C) The DPV curves of the NPG/GCE in PBS (50 mM, pH 6.0) containing different concentrations (10 to 750 μM) of uric acid. (D) The linear relationship between the oxidation peak current density of uric acid and uric acid concentration.

Figure 4

(A) Catalytic reduction of picric acid by the NPG/GCE and Jaffé reaction between picric acid and creatinine under alkaline conditions. (B) The CV curves of the NPG/GCE in NaOH (0.2 M) containing picric acid (2.0 mM, 4.0 mM, and 8.0 mM) at a scan rate of 50 mV s⁻¹. (C) The specific reaction mechanism of picric acid catalyzed by NPG. (D) The CV response of picric acid before and after adding creatinine.

Figure 5

(A) The CV curves of the NPG/GCE in NaOH (0.2 M) containing 4.0 mM picric acid at different scan rates. (B) The linear relationship between the reduction peak current density of picric acid and the scan rate. (C) The CV curves of the NPG/GCE in NaOH (0.2 M) containing 4 mM picric acid and different concentrations of creatinine (D) The linear relationship between the reduction peak current density of picric acid and creatinine concentration.

Figure 6

Influence of common compounds and ions in urine on determination of uric acid (A) and creatinine (B).