Effect of Mediator Spacing On Electrochemical and Enzymatic Response of a Ferrocene Redox Polymers

The bioelectrocatalysis of redox enzymes by redox polymers has attracted significant attention in a number of fields: in vivo biosensors, DNA hybridization assays, food freshness, and miniature biofuel cells. In this study we investigate the effect of redox polymer structure on their ability to electrically communicate with the redox centers of enzymes. We report the synthesis and characterization of two novel redox polymers: hexylferrocenyl linear poly(ethylenimine) [Fc-C6-LPEI] and propylferrocenyl linear poly(ethylenimine) [Fc-C3-LPEI]. We demonstrate that the extension of the ferrocene groups further away from the LPEI backbone eliminates the multi-wave redox behavior and the oxidative degradation observed in crosslinked films of MeFc-LPEI (Fc-C1-LPEI) in the presence of dibasic phosphate and at high pH. This leads to an increase in both the electrochemical and enzymatic stability of the sensors. Finally we show that the length of the spacer effects the ability of the different redox polymers to exchange electrons with the FAD centers of glucose oxidase GOx and that sensors with current densities greater then 1 mA/cm2 can be fabricated.