Highly Sensitive Electrochemical Detection of Reactive Oxygen Species in Living Cancer Cells Using Monolithic Metallic Foam Electrodes

Reactive oxygen species (ROS) distribute in most mammalian cells in living organisms, and play a necessary role in signaling molecule to regulate various biological processes. To quantitatively and accurately monitor the ROS level releasing from living cells, electrochemical techniques have drawn great attention and ubiquitous innovations. However, its practicability is hindered by the sluggish electron transfer and poor mass transport efficiency between functional catalysts and their supports. Herein, we develop a three-dimensional monolithic and metallic foam (Ag-wire foam) to detect one typical ROS, i. e. hydrogen peroxide (H₂O₂) in three cancer cells. The high electrical conductivity of Ag and the substrate-free configuration guarantee the rapid electron flow within the metal scaffolds. The numerical model is established to depict the concentration distributions of H₂O₂ and reaction products. It shows the inter-fiber voids throughout the foam can provide fast reactant diffusion channels and further facilitate the mass transport. We fabricate a microfluidic chip-based three-electrode system to detect the trace H₂O₂ concentration. A low detection limit of 15 nM H₂O₂ in human leukemia K562 cancer cells and less than 20 s response time 0is observed, outperforming many previous reports. Importantly, the concept of building three-dimensional metal wire foams demonstrated herein is hopeful to guide the designing and promote high-performance ROS-detection in living cells.