Fabrication\nof Nanobioengineered Interfaces Utilizing\nQuaternary Nanocomposite for Highly Efficient and Selective Electrochemical\nBiosensing of Urea

Nanobioengineered interfaces have gained attention owing\nto their\nsmall size and high surface area-to-volume ratio for utilization as\na platform for highly selective and sensitive biosensing applications\nowing to the integration of biological molecules with engineered nanomaterials/nanocomposites.\nIn this work, a novel Ag-complex, [(PPh<sub>3</sub>)<sub>2</sub>Ag(SCOf)]-based\nquaternary Ag–S–Zn–O nanocomposites (NCs), was\nsynthesized through an environmentally-friendly process. The results\nrevealed the formation of the NCs with an average crystallite size\nand particle size of 36.08 and 40.22 nm, respectively. In addition,\nthis is the first study to utilize such NCs synthesized via a single-source\nprecursor method, offering enhanced sensor performance due to their\nunique structural properties. Further, these NCs were used to fabricate\na urease (Ur)/Ag–S–Zn–O NCs/ITO nanobioengineered\nelectrode for precise and sensitive electrochemical biosensing of\nurea. The interfacial kinetic studies revealed quasi-reversible processes\nwith high electron transfer rates and linear current responses, indicating\nefficient reaction dynamics. A high diffusion coefficient and low\nsurface concentration suggested a fast diffusion-controlled process,\naffirming the electrode’s potential for rapid and sensitive\nurea detection. The biosensor demonstrated notable sensing properties\nsuch as high sensitivity (12.56 μA mM<sup>–1</sup> cm<sup>–2</sup>) and a low detection limit (0.54 mM). The fabricated\nbioelectrode was highly selective and reproducible and demonstrated\nstability for up to 60 days. These results validate the potential\nof this nanobioengineered interface for next-generation biosensing\napplications, paving the way for advanced point-of-care diagnostics\nand real-time health monitoring.