In situ potentiometric SECM monitoring of the extracellular pH changes under electrical stimulation using a dual-microelectrode tip

Different cells respond differently to environmental stimulation, resulting in different extracellular pH values. Therefore, the pH of the extracellular microenvironment (pHe) is an important manifestation of cell response to the environment. In this study, a pH-selective dual-microelectrode tip was used as the probe tip of a scanning electrochemical microscopy (SECM) instrument to in situ monitor the pHe changes of different cells after being electrically stimulated by the SECM potential method. pHe is the pH at a certain distance from the cells, and the distance is determined by substituting the current measured by the approach curve into a theoretical calculation. A gold microelectrode was used to determine the distance between the dual-microelectrode tip and the cell, and a pH-selective microelectrode was used to measure the pHe. It was found that the pHe value was related to the distance between the pH-measuring electrode and the cell, and different types of cells had different pHe changes after electrical stimulation. Through fluorescent staining with calcein-AM and propidium iodide, it was verified that this phenomenon was caused by changes in the permeability of the cell membrane due to electrical stimulation. In situ monitoring the pHe changes of different cells will be helpful for exploring the response of cells to environmental stimulation and the mechanism of these different responses.