Fabrication of uric acid chemical sensor based on tricobalt tetroxide crosslinked chitosan with gold nanoparticle modified glassy carbon electrode

Sensor technology has advanced significantly in recent years and has become an essential tool in various fields, including medicine, food analysis, and environmental monitoring. Uric acid (UA) is a biomarker for several diseases, such as gout and kidney stones. This research develops an electrochemical sensor for the determination of UA based on tricobalt tetroxide (Co3O4) and gold nanoparticles (AuNPs) in the crosslinked chitosan polymer (CHIT) and modified on the glassy carbon electrode (GCE) (Co3O4-CHIT/AuNPs/GCE). X-ray diffractometer (XRD) and scanning electron microscope (SEM) were used to characterize the synthesized Co3O4, which was crystallized in a cubic phase with a flower-like structure, while AuNPs were successfully synthesized and confirmed by UV-Vis spectroscopy. The Co3O4-CHIT/AuNPs/GCE was tested in 0.15 mM of UA using cyclic voltammetry (CV) and gave an oxidation peak at +0.61 V. The Co3O4-CHIT/AuNPs deposited on GCE exhibited the ability to oxidize the UA and obtained a higher current compared to the bare, Co3O4-CHIT, and AuNPs modified electrodes for 1.79, 2.03, and 1.47 times, respectively. The analytical specification of this sensor was studied by amperometric technique in phosphate buffer pH 7.0 at suitable parameters of applied voltage, AuNPs, and Co3O4-CHIT for + 0.65 V, 20 µL, and 60 µg, respectively. It was found that the linearity obtained from 0.5 to 700 µM (y = 0.0079x + 0.0049, R2 = 0.9996) with a limit of detection (LOD) of 0.31 µM (S/N =3) and limit of quantification (LOQ) was calculated to be 1.03 µM. We found that 0.01 mM ascorbic acid, 0.5 mM urea, 0.1 mM caffeine, 5.0 mM Cl-, 7.0 mM glucose, and 20.0 mM sucrose did not affect the UA analysis. The repeatability and reproducibility were obtained at 2.94 %RSD (n=5) and 2.30 %RSD (n=5), respectively. This sensor was applied to detect uric acid in blood samples without any preparation before the test. It showed high accuracy in terms of %recovery within the range of 96.76-104.92.