3D Neuromodulation in Neural Organoids with Shell MEAs

Neural organoids (NOs) have emerged as important tissue engineering models for microphysiological systems, brain sciences, and biocomputing. Establishing reliable relationships between stimulation and recording traces of electrical activity is essential for monitoring the functionality of NOs, especially in paradigms such as neural plasticity, learning, or stimulus discrimination. While researchers have demonstrated neuromodulation in NOs, they have primarily used 2D microelectrode arrays (MEAs) with limited access to the entire 3D contour of the NOs. Here, we report neuromodulation using tiny mimics of macroscale EEG caps, or shell MEAs. Specifically, we observe that stimulating current within a specific range (20 to 30 µA) induced a statistically significant increase in neuron firing rate when comparing the activity 5 s before and after stimulation. We detect neuromodulatory behavior using both three- and 16-electrode shells and generated 3D spatiotemporal maps of neuromodulatory activity around the entire surface of the NO. Our studies demonstrate a methodology for investigating 3D spatiotemporal neuromodulation in organoids of broad relevance to biomedical engineering models of neural functionality, plasticity, and learning.