An electrochemical sensor is provided for use in a wearable device for measuring analytes in a pH-variable biofluid. The sensor includes a plurality of aptamer sensing elements which have biorecognition elements, such as aptamers, that experience a conformational change on interaction with a target analyte in the biofluid. Each aptamer sensing element forms a first configuration before target analyte capture and a second configuration after target analyte capture. A redox moiety is paired with each aptamer sensing element. The redox moiety has a reaction potential that is at least partially independent of a pH value of the biofluid. The EAB sensor further includes an electrode operative in conjunction with the plurality of aptamer sensing elements to produce a variable signal depending upon the configuration of the aptamer sensing elements.
