Altres ajuts: 2016 Leonardo grant from the BBVA Foundation

Prussian Blue (PB)-modified graphite screen-printed electrodes are increasingly being used in electrochemical biosensors. However, they do not allow the observation of the electrochromism of PB. This work presents the construction of PB-based, electrochromic screen-printed biosensors. Although electrically more resistive than their graphite counterparts, these new PB-based electrodes enable both the amperometric and colorimetric detection of hydrogen peroxide. This is the first time that this has been achieved using screen-printed electrodes, and we demonstrate it spectroelectrochemically on a glucose biosensor. The biosensor electrochemical performance equals that of previously reported PB/graphite electrodes, being able to detect down to 4 μM H2O2 and 54 μM glucose. At the same time, and in contrast to PB/graphite electrodes, the new PB-based electrodes afford the optical detection of these two analytes down to 1.2 μM and 15 μM, respectively. The dynamic ranges of the glucose biosensors obtained at the PB-based electrodes are 0.1-1 mM (amperometric) and 0.025-2.5 mM (Colorimetric), matching the physiological glucose concentration range in body fluids other than blood or serum.