Enzyme electrodes creatine

In an early application, an enzyme electrode system was reported for the determination of creatinine and creatine, using a combination of creatinine amidohy-drolase, creatine amidinohydrolase and sarcosine oxidase, co-immobilized on an asymmetric cellulose acetate membrane. Thus, the hydrogen peroxide produced was detected to give a quantitative measure of creatine and creatinine in biological fluids [70]. 

A three-enzyme electrode system, such as needed for creatinine measurement, poses a more difficult enzyme-immobilisation problem, in that different enzymes have different immobilisation requirements and their microenvironmental interrelationships need to be optimised. For one creatine sensor, the requisite creatine amidinohydrolase and sarcosine oxidase were immobihsed in polyurethane pre-polymer and PEG-hnked creatinine amidohydrolase was attached via diisocyanate pre-polymer to create a polyurethane adduct [14]. The likelihood of enzyme inactivation with chemical immobih-sation is high, but provided an enzyme preparation survives this, long-term stability is feasible. In the case of these three particular enzymes, a loss of activity resulted from silver ions diffusing from the reference electrode the material solution was to protect the enzyme layer with a diffusion-resisting cellulose acetate membrane. 

Creatine Enzyme electrode Fixed creatinitase Diagnosis Ammonia electrode... 

ADP AFP ab as ALAT AP ASAT ATP BQ BSA CEH CK CME COD con A CV d D E E EC ECME EDTA EIA /e FAD FET FIA G GOD G6P-DH HBg HCG adenosine diphosphate a-fetoprotein antibody antigen alanine aminotranferase alkaline phosphatase aspartate aminotransferase adenosine triphosphate benzoquinone bovine serum albumin cholesterol ester hydrolase creatine kinase chemically modified electrode cholesterol oxidase concanavalin A coefficient of variation (relative standard deviation) layer thickness diffusion coefficient enzyme potential Enzyme Classification enzyme-chemically modified electrode ethylene diamine tetraacetic acid enzyme immunoassay enzyme loading factor flavin adenine dinucleotide field effect transistor flow injection analysis amplification factor glucose oxidase glucose-6-phosphate dehydrogenase hepatitis B surface antigen human chorionic gonadotropin... 

When the three-enzyme sequence based on creatinine amidohydrolase is used, any creatine present can interfere with the determination of creatinine, so two sensors are used one to determine the total creatine plus creatinine and one to determine just creatine (by only using creatine amidinohydrolase and sarcosine oxidase). Creatinine is determined by difference. Amperometric sensors are generally based on this sequence and do not suffer from interferences. They are usually designed to respond to peroxide, though some have used oxygen electrodes. Typically, Pt electrodes are used. A sensor for just creatine only requires the creatine amidinohydrolase and sarcosine oxidase sequence. 

The coreticulation described above [3] is simple to perform during multienzymatic immobilization. The required enzymes are mixed with albumin, and enough glutaraldehyde is added to cross-link the various proteins. This method is also used for the coimmobilization of creatinin amidohydrolase, creatin amidinohydrolase and sarcosine oxidase, to construct a creatinin electrode, and for the coimmobilization of a-glucosidase and glucose oxidase for the determination of starch [40]. 

---