Evaluation of two core–shell (Ag2S@- and Bi2S3@-) sensors based on a metal–organic framework (NH2-MIL-125-Ti)/polyaniline for the electroanalysis of uric acid in urine samples

Abstract

Chemical sensors for the determination of uric acid (UA) in human urine samples have been developed using a composite material based on two core–shells (Ag₂S@- and Bi₂S₃@-) coated with a metal–organic framework (NH₂-MIL-125-Ti) and polyaniline (PANI). The composite materials were characterized using Fourier transform infra-red (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX/EDX-mapping), N₂ adsorption–desorption, thermal gravimetric analysis/differential thermogravimetry (TGA/DTG), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) techniques. Differential pulse voltammetry (DPV) studies show that the oxidation peak current of UA obtained with Ag₂S@NH₂-MIL-125(Ti)/PANI/GCE and Bi₂S₃@NH₂-MIL-125(Ti)/PANI/GCE is respectively 2.45 and 2.31 times higher than the one obtained with a bare glassy carbon electrode (GCE). Calibration curves from 0 to 16 μM UA were generated after the optimization of critical parameters affecting the detection limit of UA. The sensitivities and limits of detection (LOD) obtained were 299.0 μA mM⁻¹ and 0.579 μM, 263.0 μA mM⁻¹ and 0.446 μM for Ag₂S@NH₂-MIL-125(Ti)/PANI/GCE and Bi₂S₃@/NH₂-MIL125(Ti)/PANI/GCE, respectively. The developed sensors show good selectivity, reproducibility, repeatability and storage stability at room temperature. Finally, the sensor was successfully applied for the determination of UA in human urine samples. The sensors were able to detect UA in human urine samples even after 200 times dilution, offering new hope for future point-of-care testing (POCT) devices for uric acid analysis.