The function of oxidoreductase biosensors is in general dependent on charge transport between the enzyme and an electrode surface by means of coenzymes or redox mediators. Reagentless biosensors should integrate these components within the very electrode area simultaneously preventing their leaking into the analyte medium and conserving their shuttle function. Concepts and strategies for the realization of this demand are outlined based on the structure of the active sites of the enzyme types in question and the reaction mechanism to be catalyzed. Experiences with different combinations of enzyme- and electrode-integrated mediators are reported.