Rapid prototyping of a 3D well-shaped, porous, microelectrode array for extracellular recordings from cardiac cell layers and cortical organoids

Microelectrode arrays (MEAs) can be used to record extracellular field potentials of cells, enabling investigations on neural or cardiac cellular electrical activity. However, conventionally used 2D cell monolayers cannot recapitulate the 3D microenvironment of<i>in vivo</i>tissue. Therefore, cells are grown in 3D cultures that mimic the architectural and functional aspects of human organs. MEAs that support such 3D structures are of increasing importance, but their fabrication often relies on advanced cleanroom techniques. Here, we present a fast and straightforward prototyping technique for a thin-film, porous MEA fabricated using conformal coatings and laser ablation. The absence of photolithography processes allows the MEA to be directly fabricated as a 3D structure. This advantage was exploited by manufacturing 3D, well-shaped MEAs to host cortical organoids for extracellular signal recordings. The 3D-printing-based fabrication of the wells enables the tuning of the MEA shape according to the size of the organoid. The proposed well-shaped MEAs enable easy handling and secure organoid placement by physically retaining the organoid within the well, ensuring direct alignment with underlying electrodes, avoiding the detachment issues typically encountered on 2D MEA designs. We present extracellular field potential recordings from both cardiac cells and cortical organoids.