Biosensors and flow-through system for the determination of creatinine in hemodialysate

Biosensors for the determination of creatinine have been developed and integrated into a flow-through system. The sensors are based on a screen-printed three electrode transducer with a platinum working electrode. Applying the multi-enzyme sequence of creatininase (CA), creatinase (CI) and sarcosine oxidase (SO) hydrogen peroxide has been detected amperometrically. An optimal enzyme load was found to be 4.4 U/0.28 U/0.20 U (CA/CI/SO) and 0.28 U/0.20 U (CI/SO) per electrode for the creatinine sensor and for the creatine sensor, respectively. Among a variety of polymers Nafion has shown the highest efficiency to exclude interfering substances like ascorbic acid, acetaminophen and uric acid. First determinations of creatinine in dialysate samples obtained during hemodialysis treatments have shown a good correlation to the conventional methods, the Jaffe reaction (y=0.945x+ 2.8, R=0.9882, n=9) and the enzymatic photometric method (y=0.891x+3.5, R=0.9917, n=9).