Ferrocene-Modified Linear Poly(ethylenimine) for Enzymatic Immobilization and Electron Mediation

Electrochemical glucose sensors and biofuel cells are emerging technologies that rely on the transfer of electrons between an oxidoreductase enzyme and an electrode. In electrochemical glucose sensors, the enzyme glucose oxidase (GOx) generates an electrical signal that corresponds to the amount of glucose in solution. This signal depends on communication between the electrode and the flavin adenine dinucleotide (FAD) active site in the enzyme; however, many redox-active enzymes cannot interact directly with an electrode. Instead, they rely on external relays to mediate electron transfer to/from the electrode. Mediator-functionalized polymers, such as ferrocene-modified linear poly(ethylenimine) (Fc-LPEI), can be cross-linked to immobilize the enzyme of interest in a network of electron relays. Cross-linked films of Fc-LPEI form hydrogel matrices that allow for rapid transport of glucose, while the covalently bound ferrocene groups facilitate rapid electron transfer due to their ability to exchange electrons with one another. For these reasons, Fc-LPEI films have been widely used in the development of high current density bioanode materials. This chapter describes the synthesis of a commonly used dimethylferrocene-modified linear poly(ethylenimine), as well as the subsequent preparation and electrochemical characterization of a GOx bioanode film utilizing the synthesized polymer.