High-Selectivity Nonenzymatic Creatinine Sensor Using Electrografted Ionic Liquid and Nafion for Reliable Clinical Diagnostics

The rapid and accurate detection of creatinine is essential for monitoring kidney function and diagnosing renal impairments. Nonenzymatic catalysts have been used to improve sensitivity and reduce environmental susceptibility in creatinine detection. However, limited selectivity hinders their broader application in practical scenarios. This study introduced a novel nonenzymatic creatinine sensor that utilized copper(II) oxide as a catalyst, incorporating styrenyl-triphenylphosphonium-based ionic liquid (STPP-IL) and Nafion on the electrode surface to enhance selectivity and minimize interference. Electrografting technique ensured uniform STPP-IL coverage on the electrode, as confirmed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The modified creatinine sensors demonstrated a detection range from 1.5 to 800 μM with low standard error and high sensitivities in the presence of interferents. Notably, creatinine levels in the artificial and natural human sweat were selectively quantified using the proposed sensor, supporting its potential for clinical applications. The sensors retained over 90% of their initial current response after 40 days of storage. Additionally, reproducibility experiments demonstrated a relative error of 1.3% across five independent sensors. These results show the sensor's enhanced selectivity, stability, and reproducibility, making it a promising alternative for reliable creatinine detection in point-of-care tests.