Enzyme electrode

About: Enzyme electrode is a research topic. Over the lifetime, 4103 publications have been published within this topic receiving 177157 citations.

Electrochemical Glucose Biosensors

Abstract: First-generation glucose biosensors relied on the use of the natural oxygen cosubstrate and the production and detection of hydrogen peroxide and were much simpler, especially when miniaturized sensors are concerned. More sophisticated bioelectronic systems for enhancing the electrical response, based on patterned monolayer or multilayer assemblies and organized enzyme networks on solid electrodes, have been developed for contacting GOx with the electrode support. Electrochemical biosensors are well suited for satisfying the needs of personal (home) glucose testing, and the majority of personal blood glucose meters are based on disposable (screen-printed) enzyme electrode test strips, which are mass produced by the thick film (screen-printing) microfabrication technology. In the counter and an additional “baseline” working electrode, various membranes (mesh) are incorporated into the test strips along with surfactants, to provide a uniform sample coverage. Such devices offer considerable promise for obtaining the desired clinical information in a simpler, user-friendly, faster, and cheaper manner compared to traditional assays. Continuous ex-vivo monitoring of blood glucose was proposed in 1974 and the majority of glucose sensors used for in-vivo applications are based on the GOx-catalyzed oxidation of glucose by oxygen. The major factors that play a role in the development of clinically accurate in-vivo glucose sensors include issues related to biocompatibility, miniaturization, long-term stability of the enzyme and transducer, oxygen deficit, short stabilization times, in-vivo calibration, baseline drift, safety, and convenience.

Ferrocene-mediated enzyme electrode for amperometric determination of glucose.

Abstract: for each type of enzyme but in an opposite direction for each. The type III enzyme experiences an increase in apparent Km with increasing inosine concentration, while the type V enzyme shows a slight decrease in apparent Km at high inosine concentration. The most dramatic homogeneous effect is that of increasing inosine concentration upon the VmM values, however. For the type III enzyme, apparent VmiU! is reduced by nearly a factor of 2 but, for the type V enzyme, apparent Vma, decreases more than 7-fold. Such product inhibition reveals itself through longer response times in the immobilized enzyme electrodes. The results obtained in this study show that the potentiometric ammonia gas-sensing enzyme electrode does exhibit linear responses to substrate concentrations both above and below the Km value of the adenosine deaminase enzyme when sufficient enzyme is immobilized at the electrode surface. The BSA-glutaraldehyde cross-link provides for stabilization of the enzyme activity as shown by the observed electrode lifetime. Comparison of the homogeneous kinetic parameters with those obtained from the immobilized study reveals significant changes in the kinetic properties of the enzyme when it is immobilized, possibly resulting from conformational changes in the enzyme upon exposure to BSA and glutaraldehyde. The magnitude of the effect of addition of inosine on apparent Km and Vmax depends upon whether the enzyme is immobilized or free in solution. The apparent Km for the immobilized enzyme remained essentially constant upon addition of inosine, while the apparent Km for the homogeneous enzyme did show some variation but in opposite direction for the type III and V enzymes. In the construction of enzyme electrodes, it is desirable to obtain the highest (fastest rate) and lowest Km (greatest affinity) values possible. From the results of this study carried out at high enzyme levels it is apparent that type III adenosine deaminase would be the best choice for the construction of an immobilized enzyme electrode both from the point of view of apparent Km and Vmax values and from the less pronounced product inhibition effect on the type III enzyme compared to the Type V enzyme. Even in the absence of initial inosine, type III enzyme electrodes have faster response times than corresponding electrodes prepared with type V enzyme.

Solubilization of carbon nanotubes by Nafion toward the preparation of amperometric biosensors.

Abstract: The ability to solubilize single-wall and multiwall carbon nanotubes (CNT) in the presence of the perfluorinated polymer Nafion is described. Such use of Nafion as a solubilizing agent for CNT overcomes a major obstacle for creating CNT-based biosensing devices. Their association with Nafion does not impair the electrocatalytic properties of CNT. The resulting CNT/Nafion modified glassy-carbon electrodes exhibit a strong and stable electrocatalytic response toward hydrogen peroxide. The marked acceleration of the hydrogen peroxide redox process is very attractive for the operation of oxidase-based amperometric biosensors, as illustrated for the highly selective low-potential (−0.05 V vs Ag/AgCl) biosensing of glucose. These findings open the door for using CNT in a wide range of chemical sensors and nanoscale electronic devices.

The enzyme electrode.

Abstract: The enzyme electrode is a miniature chemical transducer which functions by combining an electrochemical procedure with immobilized enzyme activity. This particular model uses glucose oxidase immobilized on a gel to measure the concentration of glucose in biological solutions and in the tissues in vitro.