Sulfonated-polypyrene aniline/polyaniline composite fortified with Cu-GQD@ZIF8 as an electrochemical enzymatic urea biosensor.

The determination of urea concentration is essential for human health owing to its crucial role in the ability to metabolize nitrogen-containing substances. This study developed new electrochemical enzymatic detection systems via the synergistic effect of the superior features of novel electropolymerizable pyranine-aniline (PA, 4), polyaniline (PANI) compounds, graphene quantum dots (GQDs) and zeolitic imidazolate framework-8 (ZIF8). The novel compound 4 was characterized via1H-NMR, 13C-NMR, FTIR, and MALDI-TOF mass spectroscopies. Furthermore, Cu-GQD@ZIF8 hybrid materials containing GQD and integrated electroactive Cu metal were prepared in this study. The surface morphology of the prepared Cu-GQD@ZIF8 hybrid material was investigated through microscopic methods such as SEM and TEM, and chemical characterizations were performed using FTIR, XPS, XRD, and TGA analyses. After the characterization of the novel materials, the urease (Urs) enzyme was bound to the new modified electrode surface. Next, the enzymatic biosensor properties of the Urs/Cu-GQD@ZIF8/PANI/PA/GCE sensor electrode for urea detection via reduction of PANI were investigated by DPV and CV techniques. The LOD and LOQ values of the presented sensor were calculated to be 0.77 μM and 2.31 μM, respectively, in the linear range of 1.0-80.0 μM, based on DPV measurements. The presented biosensor system determined the amount of urea in an artificial serum sample, and its accuracy was confirmed via the recovery test and GC-MS analysis.