Abstract

Early identification of kidney failure is crucial since it can advance silently without noticeable symptoms. Measuring creatinine, a waste product filtered by the kidneys, is an effective early diagnostic tool to prevent progression, reduce healthcare costs, and delay severe complications such as cardiovascular disease and anemia. In this study, a paper-based microfluidic sensor utilizing biogenic silver nanoparticles (AgNPs) was developed for the colorimetric detection of creatinine. AgNPs were electrochemically synthesised with Orthosiphon aristatus extract (OAE) containing flavonoids (1.71±0.16 mg/g) and phenols (23.79±1.48 mg/g) as an electrolyte and stabilising agent to produce spherical AgNPs with a size of approximately 17.44±3.68 nm. The AgNPs were then immobilised on microfluidic paper to serve as a colorimetric creatinine detector. The sensor response was evaluated using RGB (Red, Green, Blue) analysis, which compared the colour intensity before and after interaction with creatinine. The addition of creatinine replaced the OAE-derived biomolecular capping layer on the AgNP surface, confirming the ligand exchange mechanism that induces some particles might undergo agglomeration, allowing the formation of larger nanoparticles (17.44±3.68 nm to 21.09±5.92 nm) while maintaining the fcc silver crystal structure as indicated by FTIR, SEM-EDX, PSA, XRD, and TEM measurements. The developed sensor exhibited a linear range of 1–100 µg/L, with a limit of detection (LOD) of 1.6 µg/L, confirming excellent sensitivity for the early detection of kidney disease. Furthermore, the optical readout demonstrated high precision, with intra-day and inter-day relative standard deviation (RSD) values of below 4% and 6%, respectively. Even in the presence of potential interferents at tenfold higher concentrations, the sensor maintained remarkable selectivity. Application in artificial urine yielded satisfactory recovery (R) rates (96.3–102.6%), confirming that AgNP@OAE paper-based microfluidic sensor is a simple, cost-effective, and reliable tool for point-of-care creatinine monitoring and early renal diagnostics.

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