Crossectional representation of the E-AB sensor, 3D astrocyte cell culture hybrid interface. The three-electrode setup is placed inside a commercial holder (Micrux Technologies, Oviedo, Spain) with a PMMA holder on top where the 3D cell culture was polymerized, equilibrated, stimulated, and tested. Structure-switching E-AB sensors fabricated on the 1 mm working electrode allowed continuous quantification of ATP release from astrocytes.