Enzymatic biosensors have been developed for a variety of analytes, including: glucose, lactate, pesticides, nerve agents, peroxide, oxygen, and alcohols. They generally involve immobilization of an oxidoreductase enzyme on an electrode surface. Although direct bioelectrocatalysis between the enzyme and the electrode surface is the preferred mode for enzymatic biosensors, many enzymes are not capable of direct electron transfer. Therefore, mediated bioelectrocatalysis is popular in the enzymatic biosensor field, where an additional redox species is used to relay the electron between the enzyme and the electrode surface. This paper will detail the rational design of linear polyethylenimine-based redox polymers for mediated bioelectrocatalysis, where the redox polymer is used both to immobilize the enzyme and to mediate the electron transfer. This will include polymers where the ferrocene and quinone redox species is optimized for the enzymatic system employed (i.e. glucose oxidase versus glucose dehydrogenase). This paper will discuss the importance of redox potential, redox reversibility, self-exchange rate, interaction with the enzyme, and crosslinking on the properties of the polymer-modified electrodes.