Sensitive electrochemical flow injection analysis of H₂O₂ released from cells with a pass-through mode

Conventional plate electrodes were commonly used in electrochemical flow injection analysis and only part of molecules diffused to the plane of electrodes could be detected, which would limit the performance of electrochemical detection. In this study, a low-cost native stainless steel wire mesh (SSWM) electrode was integrated into a 3D-printed device for electrochemical flow injection analysis with a pass-through mode, which is different compared with previous flow-through mode. This strategy was applied for sensitive analysis of hydrogen peroxide (H₂O₂) released from cells. Under the optimal conditions (the applied potentials, the flow rate and the sample volume), the device exhibits high sensitivity toward H₂O₂. Linear relationships could be achieved between electrochemical responses and the concentration of H₂O₂ ranging from 1 nM to 1 mM. The excellent analytical performance of the SSWM-based device could be attributed to the pass-through mode based on the mesh microstructure and intrinsic catalytic properties for H₂O₂ by stainless steel. This approach could be further successfully extended for screening of H₂O₂ released from HeLa cells with electrochemical responses linear to the number of cells in a range of 3 - 1.35 × 10⁴ cells with an injection volume of 30 μL. This study revealed the potential of mesh electrodes in electrochemical flow injection analysis for cellular function and pathology and its possible extension in cell counting and on-line analysis.