Creatinine and urea biosensors based on a novel ammonium ion-selective copper-polyaniline nano-composite

M. Zhybak, V. Beni, M.Y. Vagin, E. Dempsey, A.P.F. Turner, Y. Korpan

The use of a novel ammonium ion-specific copper-polyaniline nano-composite as transducer for hydrolase-based biosensors is proposed. In this work, a combination of creatinine deaminase and urease has been chosen as a model system to demonstrate the construction of urea and creatinine biosensors to illustrate the principle. Immobilisation of enzymes was shown to be a crucial step in the development of the biosensors; the use of glycerol and lactitol as stabilisers resulted in a significant improvement, especially in the case of the creatinine, of the operational stability of the biosensors (from few hours to at least 3 days). The developed biosensors exhibited high selectivity towards creatinine and urea. The sensitivity was found to be 85±3.4mAM(-1)cm(-2) for the creatinine biosensor and 112±3.36mAM(-1)cm(-2) for the urea biosensor, with apparent Michaelis-Menten constants (KM,app), obtained from the creatinine and urea calibration curves, of 0.163mM for creatinine deaminase and 0.139mM for urease, respectively. The biosensors responded linearly over the concentration range 1-125µM, with a limit of detection of 0.5µM and a response time of 15s. The performance of the biosensors in a real sample matrix, serum, was evaluated and a good correlation with standard spectrophotometric clinical laboratory techniques was found.