Patch-Clamp-Like Micropipette Electrode with Exterior and Interior Interfaces for Simultaneous Monitoring of Extracellular and Intracellular Serotonin Across Neuron

Simultaneous monitoring of intracellular and extracellular serotonin (5-HT) across five orders of magnitude is crucial for understanding 5-HT-related diseases. Here, we created a patch-clamp-like micropipette electrode with double sensing interfaces, in which gold nanoparticles were coated onto exterior surface and conductive hydrogel was in situ polymerized by designed monomer to form interior interface. Furthermore, we engineered serotonin binding protein (SerBP) as recognition element to develop open-circuit potentiometric 5-HT sensor and modulated SerBP to enhance dissociation constant toward 5-HT through key residue mutation to broaden the linear ranges by five orders of magnitude for both intracellular and extracellular 5-HT recording. Meanwhile, the designed noninsertion mode together with zero potential detection caused minimal cell damage, thus significantly prolonged the recording duration. Using this powerful tool, we first discovered 5-HT transporter reversed function to release 5-HT before intracellular exocytosis enhanced, and together, through the release–reuptake–metabolism cycle, dynamically regulate the concentration of 5-HT with the development of seizure.