Here, we develop the first universal enzymatic O2 scavenger that is compatible with oxidasebased electrochemical biosensors, utilizing alcohol oxidase and catalase. This system catalyzes the reaction between a reducing agent (paraformaldehyde or ethanol) and O2 to yield water as the sole product from O2 reduction (Figure ). We selected alcohol oxidase as catalyst for O2 scavenging because it exclusively uses O2 as electron acceptor owing to a ternary-complex mechanism requiring simultaneous O2 and substrate binding in the catalytic active site for the substrate oxidation (Figure ) . This unique characteristic among oxidases ensures that no other natural or synthetic electron acceptors can capture electrons from alcohol oxidase, conferring crucial specificity in O2 scavenging systems that is currently lacking in biosensors utilizing oxidases. A second useful feature of alcohol oxidase is that, in addition to catalyzing the oxidation of short-chain primary aliphatic alcohols to aldehydes and H2O2 using O2, it also catalyzes the oxidation of formaldehyde to formate . Since formaldehyde is rapidly generated in situ from the hydrolysis of paraformaldehyde, we used the latter as a non-volatile precursor for the substrate of the alcohol oxidase. This greatly facilitates the handling and storage of the sensors for point-of-care applications. formate and thus reduces O2 to H2O2 which is further reduced to water through the combined reactions of catalase and AOx. AOx may use either formaldehyde as substrate producing formate or short chain, primary, aliphatic alcohols producing aldehydes. e) Ternary complex mechanism of AOx, showcasing simultaneous docking of both oxygen and the alcohol substrate to realize highly specific oxygen scavenging.