To confirm the absence of unwanted cross-reactions between GOx and the substrates of AOx, we conducted experiments involving GOx, AOx, CAT, the reducing agent for AOx (paraformaldehyde or ethanol) and either the electron mediators Fc(MeOH)2 (Figure ) or the Os-complex modified polymer (Figure ). The resulted CVs show solely the reversible redox wave of the mediator. The absence of a catalytic current demonstrates that GOx does not oxidize ethanol or paraformaldehyde.