Novel creatine biosensors based on all solid-state contact ammonium-selective membrane electrodes

Novel creatine bienzymatic potentiometric biosensors were prepared by immobilizing urease and creatinase on all solid-state contact PVC-containing palmitic acid and carboxylated PVC matrix membrane ammonium-selective electrodes without inner reference solution. Potentiometric characteristics of biosensors were examined in physiological model solutions at different creatine concentrations. The linear working range and long-term sensitivity of the biosensors were also determined. The creatine biosensors prepared by using the carboxylated PVC membrane electrodes showed more effective performance than those of the PVC containing palmitic acid membrane electrodes. Creatine assay in serum samples was successfully carried out by using the standard addition method.

An Amperometric Enzyme Electrode for Creatine Determination Prepared by the Immobilization of Creatinase and Sarcosine Oxidase in Poly(vinylferrocenium)

A new enzyme electrode for the determination of creatine was developed by immobilizing creatinase (CI) and sarcosine oxidase (SO). The enzymes were co-immobilized in a poly(vinylferrocenium) matrix onto the surface of a platinum working electrode. Crosslinking with glutaraldehyte (GA) and bovine serum albumin (BSA) was selected as the best immobilization method for the enzymatic system. Determination of creatine was performed by the oxidation of enzymatically generated H2O2 at + 0.7 V vs. Ag/AgCl. The linear working range of the electrode was 2.0 x 10(-5) - 3.2 x 10(-4) M and the response time was about 50 s. The effects of pH, temperature, enzyme ratio and buffer concentration were investigated and optimum parameters were found to be 7.5, 37 degrees C, 2.5:1 (CI:SO) and 0.05 M, respectively. The stability and reproducibility of the enzyme electrode have been also studied.