A paper-based dual-pad enzymatic sensor for rapid and low-cost point-of-care creatinine quantification

The accurate and timely assessment of renal function is crucial for screening, diagnosing, and managing kidney disease, as well as preventing contrast-induced nephrotoxicity. Here, we report a dual-pad enzymatic creatinine quantification sensor (Cre-Q sensor) for rapid, low-cost, point-of-care blood creatinine measurement. The Cre-Q sensor employs a four-enzyme cascade (creatinine amidohydrolase, creatine amidinohydrolase, sarcosine oxidase, and horseradish peroxidase) to generate a colorimetric signal proportional to creatinine concentration, with ascorbate oxidase incorporated in the sample pad to eliminate ascorbic acid interference. The sensor requires 15 μL of serum, delivers results in 10 min, at an estimated material cost of USD 0.05 per strip (excluding labor and packaging). The sensor exhibited a quadratic calibration curve (R² = 0.99) over the 0–20 mg/dL range, a limit of detection of approximately 0.0137 mg/dL, and robust stability (≤7% signal loss over 30 days at 4 °C). Clinical evaluation using 74 samples yielded R² = 0.97 against the Cobas 8000 c702, with 100% sensitivity, 97.22% specificity, and receiver operating characteristic area under the curve (ROC AUC) of 0.9985. The low cost, ease of use, and robust analytical performance of the Cre-Q sensor support its potential application for rapid renal function testing in emergency, radiology, and resource-limited settings.