The behavior of each type of sensor was studied by cyclic voltammetry in a potential range from 200 mV to 500 mV at a scan rate of 10 mV/s in 0.1 M phosphate buffer pH 7 (KH2PO4/Na2-HPO4 + KCl 0.1 M) containing 1 mM acetylthiocholine chloride (ATChCl).