Silver conjugated nickel oxide nanoparticle dependent microfluid non-enzymatic colorimetric paper-based biosensor for uric acid detection

The current investigation aims to develop simple, cost-effective and user-friendly silver (Ag) conjugated nickel oxide (NiO) nanoparticle-dependent wax screen-printed microfluid paper-based non-enzymatic colorimetric biosensors to determine the UA concentration. This mechanism is based on the enzyme-like activity of NiO@PVP@Ag nanoparticle that catalyse the UA hydrolysis to yield hydroxyl radical through the colour change of 3,3′,5,5′-tetramethylbenzidine. The synthesized NiO, Ag and NiO@Ag nanoparticles have been characterized through various techniques. Structural variations in the surface of designed microfluidic paper have been subjected to morphological analysis. NiO@PVP@Ag nanoparticle exhibited strong catalytic performance with the Km (Michaelis-Menten constant) and Vmax (maximum reaction velocity) values of 4.5 μM and 3.133 × 10⁻⁶ mM s⁻¹ respectively of UA. Both visual observation and UV-Vis spectroscopy verified the colorimetric shift from blue-green to light blue. The detection limit of UA in deionized water, phosphate buffer saline (PBS) and simulated body fluids (SBF) has been determined in the corresponding order of 0.06, 0.11 and 0.03 μM. The image J results provide a linear range with a UA concentration of 1–5 μM and a detection limit (LOD) in the range of 1.5–1.7 μM. The proposed sensor deliberates the potential to detect UA in the range of 0.8–0.07 μM, which is 10-fold higher than the normal range of UA levels in blood bloodstream.