To confirm the absence of cross-reactions occurs 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.