Tailoring enzymatic membranes for ENFETs for dialysis monitoring

We report here, for the first time, the tailoring of enzymatic membranes (enzyme origin, type of photocurable polymer, formulation of the membrane, conditions of deposition) in order to obtain ENFETs with specifications adapted to dialysis monitoring through direct detection of creatinine and urea in plasmatic liquid. Creatinine deiminase was immobilised in a PVA/SbQ membrane on the dielectric gate of a pH-sensitive ISFET, this membrane being deposited at the end of the microtechnological process and then processed using photolithography. Detection limit obtained in a model solution was about 20 /spl mu/M. A novel urea biosensor based on immobilised recombinant urease as sensitive element and ion sensitive field effect transistor (ISFET) as transducer was developed. Recombinant urease from E.coli with an increase Km was photoimmobilised in PVA/SbQ membrane and has demonstrated quite good performance as biosensitive element. The working characteristics of the ENFET based on such a bioselective element were studied in model buffer solutions. This biosensor demonstrated an extended dynamic range up to 80 mM, a quite good reproducibility and a high stability.