pH-ISFET based urea biosensor

A new method of direct immobilization of urease on a hydrated silicon nitride surface with the use of glutaraldehyde is presented. The main parameters characterized the developed mts biosensor based on pH-ion-selective field effect transistor (pH-ISFET) with directly immobilized urease are: (1) maximal analytical signal, 120-140 mV in 10 mM phosphate buffer solution; (2) linear range of Delta U-gs=f(log C-urea):pC(urea)(2-3.5) in 10 mM phosphate buffer: (3) response time, 80 s; and (4) lifetime of 35 days with a stable analytical sinal. The biosensor was used for urea determination in blood serum and is hemodialysis fluid with satisfactory results. (C) 1997 Elsevier Science S.A.