Integration of electric circuits into tailor-made 3D nanoprinted microscaffolds for neuronal network cultivation

Microelectrode arrays (MEAs) for non-invasive electrical readout of neurons are a valuable tool for long-term studies of neuronal network signaling on a single-cell level. However, conventional MEAs are built only in 2D and thus do not represent the three-dimensional network topology of the human brain. Here, we present an approach to equip planar MEAs with 3D microscaffolds featuring circuitry for enabling three-dimensional brain-on-a-chip devices with single-cell outgrowth control and electrical readout. Recently, we presented non-functional microscaffolds prepared by 3D nanoprinting (3DN) for enabling human induced pluripotent stem cell (hiPSC)-derived guided neuronal networks in 3D. However, the electrophysiological readout was limited to invasive patch clamp measurements of selected cells from the network. For future collective long-term experiments, integrated electrodes inside the scaffolds are prepared by electrodeposition (ED) of gold. Specifically, by implementing vertical tunnels into the microscaffolds at the readout positions during 3DN, the gold deposition was precisely guided. The 3DN was conducted directly on MEAs to address each electrode individually until the deposited gold filled the tunnels. Note, the electrode’s surface topography can be tuned by changing the deposition rate which allows for optimizing the cell-electrode coupling. The versatile nature of the MEA fabrication in combination with 3DN and ED enables the production of addressable electrodes within the third dimension of almost any shape. Thus, our results take a significant step toward application in analyzing information transmission within neuronal networks and understanding the underlying mechanisms orchestrating information processing in 3D.SEM images of a) microscaffold with b) integrated circuitry.