Electroanalytical Studies of Immunoglobulin-Bound Glucose Oxidase

Abstract

Typically, enzymes are immobilized in inorganic, sol-gel, or polymeric matrices for applications in enzyme-based biosensors. In this report, the feasibility of using immunoglobulin ͑IgG͒ as an immobilization matrix for glucose oxidase ͑GO͒ was investigated. The effects of binding GO to IgG on its enzymatic activity and kinetics were studied using cyclic voltammetry and scanning electrochemical microscopy. These studies indicated a comparatively small reduction in the enzyme-mediator reaction rate when the GO enzyme was bound to IgG, against other immobilization methods. The turnover numbers for IgG-bound GO adsorbed on gold and glass substrates were 475-740 and 103-354 s −1 , respectively, using ferrocenemethanol as a mediator. Finally, the suitability of the IgG-based immobilization method to entrap GO on the electrode surface was demonstrated in an amperometric glucose biosensor fabricated using physically adsorbed IgG-bound GO immunocomplex on a gold electrode. Development of new methodologies and materials for the immobilization of biological molecules is an exciting and important research area in bioanalytical, environmental, and biomedical applications, including biosensors, bioaffinity chromatography, and bioreactors, besides being useful for fundamental biochemical and biophysical studies. 1 In electrochemical biosensors, many matrices have been shown to be suitable for the entrapment of biological molecules. 1-3 Typically, biological molecules are entrapped within these matrices by mixing the solutions containing biological molecules and the matrix components and subsequently applying them as a coating over the sensing electrode. Other methods include direct physical mixing of the enzyme molecules into electrode materials such as carbon paste. 4 Physical entrapment of biological molecules during electrodeposition of conductive polymers 5 and metals 6 are also convenient single-step methods that are rapid and readily controlled.Monolayers and multilayers of immunoglobulin G ͑IgG͒ structures have been routinely used in enzyme-linked immunoassay analysis and electrochemical immunoassay techniques. 7-11 The use of immunoglobulin monolayer as an immobilization matrix for enzymes is not new and has been applied for the detection of glucose in flow injection systems. 12,13 Glucose oxidase bound to its specific antibody was found to be stable and active. 14 In this report, we study the enzyme activity of surface adsorbed IgG-bound glucose oxidase enzyme using scanning electrochemical microscopy and demonstrate the feasibility of using IgG as the immobilization matrix for glucose oxidase ͑GO͒ in an electrochemical biosensor.Herein, the activities of surface-bound IgG-GO are investigated for two different surfaces: gold and glass. Glucose oxidase enzyme was chosen because it is one of the most studied enzymes in enzyme-based biosensors. The heterogeneous activities of the enzyme were compared to its homogeneous values in the presence and absence of IgG. Finally, the suitability of the IgG-based immobilization meth...

In Situ Confinement of Ultrasmall Metal Nanoparticles in Short Mesochannels for Durable Electrocatalytic Nitrate Reduction with High Efficiency and Selectivity

“…[2,23,25,26] For example, metal alloys on various substrates, including carbon nanotubes, graphite, Ti, and γ-Al 2 O 3 have been rationally designed for highly efficient removal of nitrate. [27][28][29][30][31] Nevertheless, these metal alloy catalysts easily suffered from severe aggregation and leaching during the continuous polarization, resulting in the rapid activity decay and low reproducibility in practical applications. In contrast, mesoporous carbon materials possess high surface areas, large pore sizes, excellent electrical conductivity, good corrosion resistance, and low cost, and thus have been regarded as the most promising catalyst supports for widespread applications.…”