Immobilization of polyglutamate-glucose oxidase onto a cysteamine-modified gold electrode

Polyglutamate–glucose oxidase (GOD) complex was prepared, and the complex was dropped on a cysteamine-modified gold electrode to immobilize the complex; the electrostatic binding between the cysteamine on the electrode surface and the polyglutamate moiety of the complex resulted in the formation of a GOD-attached electrode. The enzyme electrode showed quick response (∼15 s), since the enzyme layer was quite thin (enzyme-complex monolayer structure). When we use un-modified GOD instead of polyglutamate–GOD, the sensitivity of the resulting enzyme electrode was quite low. This clearly shows that the presence of polyglutamate chain of the complex is essential for the immobilization of the modified electrode surface, i.e., the polyglutamate moiety acts as an anchor part for the complex. A linear relationship between the current response on the complex immobilized electrode and the glucose concentration was observed between 5 and 100 μM. The immobilization technique can widely be applied to prepare biosensors and biochips.