title: Use of competitive inhibition for driving sensitivity and dynamic range of urea ENFETs.
abstract: An urea biosensor based on urease-BSA (bovine serum albumin) membrane immobilised on the surface of an ion-sensitive field effect transistor (ISFET) has been studied in a mix buffer solution composed of potassium phosphate, Tris, citric acid and sodium tetraborate. In this mix buffer, the biosensor showed a dynamic larger than the one observed in a phosphate or Tris buffer. Investigation of the individual effect of each component of the buffer solution on the biosensor response has shown that tetraborate anion acts as a strong competitive inhibitor for the hydrolysis reaction of urea catalysed by urease. The biosensor response was investigated in a phosphate buffer with different concentrations of tetraborate anion. The results showed that the apparent constant of Michaelis-Menten, K(m(app)), increases from 4.3 to 79.3 mM, for experiments realised without and with 0.5 mM sodium tetraborate, respectively. The mean value, determined graphically, for the inhibition constant, K(i), was 29 microM. The graphical representation of biosensor calibration curves in semilogarithmic co-ordinates showed that the linear range of the biosensor can be extended up to three orders of magnitude, allowing an urea detection in a concentration range 0-100 mM.
authors.affiliation: Laboratoire d'Ingénierie et Fonctionnalisation des Surfaces, UMR CNRS 5621, Ecole Centrale de Lyon, 36 Avenue Guy de Collongue, 6913 Ecully Cedex, France.
authors.forename: J V
authors.initials: JV
authors.lastname: de Melo
authors.forename: A P
authors.initials: AP
authors.lastname: Soldatkin
authors.forename: C
authors.initials: C
authors.lastname: Martelet
authors.forename: N
authors.initials: N
authors.lastname: Jaffrezic-Renault
authors.forename: S
authors.initials: S
authors.lastname: Cosnier
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D001881:Borates / Q000737:chemistry*; D020099:Coated Materials, Biocompatible / Q000138:chemical synthesis; D004563:Electrochemistry / Q000295:instrumentation* / Q000379:methods; D004789:Enzyme Activation; D004800:Enzymes, Immobilized; D004867:Equipment Design; D006863:Hydrogen-Ion Concentration; D007477:Ions; D008567:Membranes, Artificial; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D014173:Transistors, Electronic; D014508:Urea / Q000032:analysis* / Q000037:antagonists & inhibitors / Q000737:chemistry; D014510:Urease / Q000737:chemistry*
chemical_list: D001881:Borates; D020099:Coated Materials, Biocompatible; D004800:Enzymes, Immobilized; D007477:Ions; D008567:Membranes, Artificial; D012710:Serum Albumin, Bovine; D014508:Urea; C010634:sodium borate; D014510:Urease