High-Performance Electrochemical Creatinine Biosensor Based on Β-Lead Dioxide/Single-Walled Carbon Nanotube Electrode

Abstract

Creatinine is an important biomarker of kidney function and muscular metabolism. In this paper, we developed the β-lead dioxide/single-walled carbon nanotube (β-PbO2/CNT) and the β-PbO2/CNT ion-selective electrode (β-PbO2/CNT/ISE), which were used as highly sensitive potentiometric biosensors for creatinine detection. The fabricated electrodes exhibited highly pH-sensitive characteristics due to the synergistic effect of the electrochemical properties of CNT and β-PbO2. Moreover, an ammonium-ion-selective membrane coating allowed the β-PbO2/CNT electrode to be NH4+-selective for direct detection of the ammonium ion. By exploiting the electrochemical characteristics of these electrodes, the creatinine assay was established through the one-step selective conversion of creatinine by creatinine deiminase, in which the OH– and NH4+ generated by enzymatic reaction were detected using β-PbO2/CNT and β-PbO2/CNT/ISE electrodes as pH- and NH4+-responsive biosensors, respectively. The total creatinine assay can be completed within ~5 min. The assay results from β-PbO2/CNT and β-PbO2/CNT/ISE showed excellent sensitivity values of -75.56 mV and 64.62 mV in the detection range of 10–400 μM with a fast response (20 s), and the limits of detection were calculated to be 0.06 μM and 0.13 μM, respectively. Moreover, the developed creatinine biosensor showed high selectivity against 11 interfering bio/chemical species with negligible interferences (selectivity coefficient < 10-4), and excellent repeatability (> 97% within 25 cycles) and long-term stability for four weeks of storage. In addition, the feasibility and practicality of the device were successfully demonstrated in human serum tests with recoveries of 95–104% for PbO2/CNT and 92–110% for PbO2/CNT/ISE.

Keywords: Creatinine, Electrochemical sensor, Potentiometry, single-walled carbon nanotube, lead dioxide, point-of-care