Monitoring dynamic release of intracellular hydrogen peroxide through a microelectrode based enzymatic biosensor

A high sensitive and selective hydrogen peroxide (H₂O₂) biosensor was fabricated on the basis of reduced hemoglobin (Hb) and single-walled carbon nanotubes (SWCNTs) for detecting the release of H₂O₂ from living HepG2 cancer cells in the process of the in situ biosynthesis of ZnO quantum. The modification of carbon fiber microelectrode (CFME) was carried out by physical adsorption. By the scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), the dense cover of surface and successful immobilization were characterized. Electrochemical investigation demonstrates that the as-prepared modified microelectrode showed a quasi-reversible process toward the reduction of H₂O₂, which exhibited a linear range from 0.51 to 10.6 μM, with a limit of detection of 0.23 μM. This microelectrode biosensor was applied for the quantification of the change of H₂O₂ concentration released from HepG2 cells through the in situ biosynthesis of ZnO quantum dots, which was further confirmed by the fluorescence staining.