An analyte sensor comprising: an insertion tip configured for insertion below a tissue of a user, the insertion tip comprising: a working electrode comprising a sensing layer disposed thereon and a membrane layer disposed at least partially over the sensing layer； a substrate； and a counter electrode. Wherein a polymer layer comprising at least an immunosuppressant is disposed on an exterior surface of the working electrode, the substrate, or the counter electrode, the polymer layer being separate from the sensing layer and the membrane layer.
