AC-electrophoretic deposition of metalloenzymes: Catalase as a case study for the sensitive and selective detection of H2O2

The deposition of metalloenzymes on electrodes in their highly active state using electric fields is challenging because the presence of metal cations within the enzyme structure renders the enzyme more fragile and high applied currents or voltages may pull out the metal cations from the enzyme structure and lead to its denaturation. In this study, we demonstrate that catalase, a metalloenzyme with four porphyrin heme Fe(III) groups can be deposited using AC-EPD to yield highly active enzyme layers. Under the optimal deposition conditions of 30 Hz, 160 Vp–p and 30 min deposition time using an unbalanced triangular waveform, the catalase enzyme electrode had a sensitivity for H2O2 of 32.5 nA/μM mm2 at a polarization potential of −0.1 V vs. Ag/AgCl. The sensor has a linear response up to 90 μM H2O2, a fast response time of 4 s, a detection limit below 1 μM and a reasonable stability without employing stabilizers or an outer polymer layer.