Multi-enzyme electrode using hydrogen-ion-sensitive field-effect transistors

Performance Characteristics of a Urea Microsensor Employing a Micromachined Carbon Dioxide Electrode

“…This means that the response becomes faster for the same concentration of urea by increasing the activity of the enzymeimmobilized membrane. Additionally, because the equilibrium relations including CO 2 yHCO À 3 and NH 3 yNH 4 are involved, urea sensors reported previously showed dependence of the response time on pH, which becomes faster at higher pHs [6,18]. The same tendency was observed with our urea sensor.…”

“…The long response time has also been experienced with an ISFET-based urea sensor without a gas-permeable membrane [6]. In view of the response time of the carbon dioxide electrode, it is considered that a relatively long time is required for equilibrium to be established among related pH-determining species in the enzyme-immobilized membrane.…”

Recent developments in urea biosensors

“…Bovine serum albumin (BSA) has been widely used for the immobilization of urease on a transducer surface via chemical cross-linking [133,134]. Apart from all these methods, silanization is most commonly used [135][136][137][138][139][140][141][142][143]. This procedure enables the introduction of chemically reactive groups.…”

Advances in the Microfabrication of Electrochemical Sensors and Systems

“…When used in a potentiometric sensor, it has been used directly as a potential standard in combination of a micro-indicator-electrode or as the third electrode in an ISFET-REFET (reference ®eld-effect transistor) con®guration mentioned next (Fig. 3b) [63,64]. Needless to say, the potential of this type of reference electrode is affected by the variation of the activity of the primary ions which determine the potential.…”

“…A couple of examples of the combination of target analytes include glucose and triolein [106], glucose and urea [63,64,106]. Examples of integration are also found with the ion-selective electrodes.…”