A novel flexible electrochemical sensor with multi-level carbon nano-array for in-situ real-time monitoring of H2O2 secreted by cells

Developing ultra-sensitive sensors for in-situ real-time monitoring of low-level cell secretions is of paramount importance in understanding various biological processes, and it is still a challenge. Herein, for the first time, we constructed a novel flexible Au-Co@C-CNT/CC sensing electrode with nano-array structures by in-situ synthesis, catalytic pyrolysis and electrochemical deposition, and successfully realized the real-time monitoring of H2O2 released by cells. The 3D leaf-like structure of the electrode not only provided a large electroactive surface area (7.66 cm2) but also exhibited a microvilli structure of carbon nanotubes (CNT) on the surface, which further enhanced the presence of active sites. Moreover, the Co-Nx sites generated by catalytic pyrolysis can promote the adsorption and catalysis of H2O2 on the surface of sensing electrode. The introduction of Au NPs facilitated the transfer of electrons, thereby enhancing the electrical conductivity and electrocatalytic performance of Au-Co@C-CNT/CC. Benefiting from these unique superiorities, this sensing platform displayed excellent performance for H2O2 determination with a wide linear range (10–27080 μM) and low detection limit (0.13 μM). Notably, the good biocompatibility and flexibility of this sensing platform allowed direct culture of human lung cancer cells (A549 cells) on the electrodes, which can realize dynamic in-situ real-time detection of H2O2 released by cells, showing great potential in the diagnosis of related diseases.