Creatinine-Iron Complex and Its Use in Electrochemical Measurement of Urine Creatinine

A non-enzymatic electrochemical technique for creatinine sensing is presented, exploiting iron binding property of creatinine. Disposable carbon printed electrodes layered with FeCl₃ coated cotton fiber membranes are used to sense creatinine from 10 to 245 mg/dl, on clinical urine samples. The energydispersive X-ray spectroscopy analysis confirms the presence of Fe(III) dry chemistry on cotton membrane. Creatinine binding with Fe(III) is verified with UV analysis, with a corresponding decrease in Fe(III) reduction current in cyclic voltammetry. The disposable test strips are interfaced with multi-potentiostat point of care (POC) hand-held device, working in amperometry mode. The results obtained on POC biosensors demonstrate good correlation (R² = 0.91) with Jaffe method laboratory gold standard. The intra-assay variability is less than 7.1%. The statistical bias as revealed from the Bland-Altman analysis indicates that the POC results are within 95% confidence interval. This POC device does not require any sample preparation step and provides sample to result in less than a minute. FeCl₃ sensing chemistry is robust against urine albumin interference, which is especially significant for accurate estimation of albumin to creatinine ratio. The non-enzymatic nature of disposable test strips results in highly stable and robust operation of the POC device over a large range of temperature variations.