Fast O2 scavenging can be achieved with the use of enzymatic O2 scavengers. The most commonly used is glucose oxidase coupled with catalase in the presence of glucose as a reducing agent, leading to effective O2 scavenging for many applications . It is generally compatible with electrochemical biosensors based on reductases , but typically incompatible with oxidase-based biosensors. The first issue is an overlap in substrate specificity between the oxidase used for O2 scavenging and the oxidase used for sensing. This problem can often be mitigated, given the vast biodiversity that offers a wide range of highly specific oxidases. The second, more challenging issue remains unresolved: while oxidases are generally specific to their substrate, they tend to be highly promiscuous with electron acceptors. The catalytic mechanism of oxidases typically follows a so-called ping-pong mechanism (Figure ) , where the enzyme is first reduced by the substrate and then reoxidized, either by its natural electron acceptor (O2) or by artificial electron mediators designed to shuttle electrons in second-generation electrochemical biosensors . Consequently, artificial electron acceptors, such as Os-complexes or ferrocene derivatives commonly used in oxidase-based biosensors, may also accept electrons from the oxidase employed for O2 scavenging. This can interfere with the anodic electron transfer involved in the sensing function.