A three-dimensional hydrogel-modified indium tin oxide electrode with enhanced performance for in situ electrochemical detection of extracellular H 2 O 2 .

Two different electrochemical sensors (Hemin-G4/Au/GCE and Hemin-G4/Au/ITO) were developed and applied to explore the electrocatalytic capacity of H ₂ O ₂ reduction. Due to the excellent catalytic activity of Hemin-G4 and high conductivity of gold nanoparticles, both electrodes show excellent electrochemical performances towards H ₂ O ₂ with a low LOD (0.67 μM for Hemin-G4/Au/GCE and 0.65 μM for Hemin-G4/Au/ITO), rapid response (<4 s), and high selectivity and sensitivity (314.33 μA mM ^-1 cm ^-2 for Hemin-G4/Au/GCE and 322.22 μA mM ^-1 cm ^-2 for Hemin-G4/Au/ITO). The two electrodes allow sensitive capture of H ₂ O ₂ produced by A549 cells. Compared with the conventional method of detection in cell suspensions, an ITO electrode with a large specific surface area and good biocompatibility can provide a promising platform for cell adhesion, so as to realize real-time and in situ detection of extracellular H ₂ O ₂ . The experimental results show that A549 cells can adhere to the surface of the Hemin-G4/Au/ITO electrode and grow well. This is benefitted from the three-dimensional structure of the Hemin-G4/Au hydrogel, which provides a suitable microenvironment for cell adhesion and growth. Furthermore, the in situ detection shows a faster response time than that of in-solution detection. This is because the H ₂ O ₂ generated by the cells can be directly captured by the ITO electrode, which avoids diffusion from the solution to the electrode. These results indicate that the self-supporting hydrogel modified ITO electrode has great application prospects in basic biomedical research and continuous dynamic surveillance of diseases.