A highly sensitive amperometric creatinine sensor

Highly sensitive amperometric creatinine sensors based on the adsorption of three enzymes are described. The base electrodes are fabricated using electrochemical deposition of Pt black on a flexible electro-conductive polymer film (polyanion doped polypyrrole). The multienzyme system (creatininase, creatinase and sarcosine oxidase) is adsorbed at the Pt black matrix. After drying a thin gelatin layer is cast on the enzyme adsorbed film and cross-linked under dry conditions by dipping into a diluted glutaraldehyde solution for 30 s. The sensor performance is evaluated using a batch analysis and a stop flow analysis by applying a continuous polarization potential of 0.4 V vs. AgAgCl at 25 °C. The sensitivity of the developed sensors is dependent on the preparation condition, the source of sarcosine oxidase, the composition of the three enzymes in the adsorbing/casting solution and the Pt black loading. A sensitivity of 23 μA/mM cm−2 and an extended linear range upto 5 mM level with a detection limit of 1–2 μM are obtained. At certain compositions of these three enzymes creatine does not produce any significant response current up to the physiological maxima of 1 mM, which makes the system virtually free from creatine interference. The operational stability of the response current of the developed sensor is also described.