USA — Microfabricated biosensors : In ANAL. CHIM. ACTA (319/3 (335–345) 1996) M.B. Madaras, I.C. Popescu, S. Ufer & R.P. Buck of the University of North Carolina report on ‘Microfabricated amperometric creatine and creatinine biosensors’
✍ Scribed by Valerie M. Owen
- Publisher
- Elsevier Science
- Year
- 1996
- Tongue
- English
- Weight
- 96 KB
- Volume
- 11
- Category
- Article
- ISSN
- 0956-5663
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✦ Synopsis
constant, k(s), of the reaction between the reduced enzyme and the mediator for native and deflavo enzymes were determined to be (10.2 _+ 0.5) x 104 M 1 s 1 and (9.6 _+ 0.5) x 104 M 1 s i, respectively. The deflavo enzyme was effectively stabilized by 5 mM EDTA in Tris buffer, pH 8 at 277 K and retained about 80% of its activity after several days when stored in this medium. The deflavo enzyme was cross-linked by glutaraldehyde and retained onto the sensing area of a glassy carbon electrode by a porous Nylon membrane with a pore size of 5 lam. The limiting catalytic current attained a maximum value around an enzyme loading of about 0.12 nmol/cm 2. The k(s) value was estimated to be 1.64 x l04 M ~ s -~ which was six-fold lower than the value obtained for the homogeneous enzyme system. The biosensor with immobilized deflavo enzyme showed high operational and storage stabilities with a detection limit of about 0.1 pM for hypoxanthine. No significant sensitivity loss was observed on the enzyme electrode after 150 repeated analyses during a 7.5-h operation. The deflavo enzyme biosensor retained 80% of its sensitivity when stored at 277 K after a month.