Thin-film and disc electrodes were functionalized into aptamer sensors using similar processes. Specifically, our disc electrodes required an additional cleaning step before functionalization with aptamer in which we mechanically polished them using micro cloths soaked in 0.3 µm alumina slurry (eDAQ, Colorado Springs, CO). Both electrode types were then electrochemically cleaned using cyclic voltammetry in base followed by acid similar to prior work . After cleaning, we incubated the electrodes in 400 nM aptamer (sequences provided in table ) for 1 h at room temperature followed by overnight incubation in 5 mM 6-mercapto-1-hexanol (mercaptohexanol) at 4°C. For in-vivo testing the aptamer sensors were disinfected using CIDEX solution as reported previously .