Bioelectrical interfaces with cortical spheroids in three-dimensions

Objective.Three-dimensional (3D) neuronal spheroid culture serves as a powerful model system for the investigation of neurological disorders and drug discovery. The success of such a model system requires techniques that enable high-resolution functional readout across the entire spheroid. Conventional microelectrode arrays and implantable neural probes cannot monitor the electrophysiology (ephys) activity across the entire native 3D geometry of the cellular construct.Approach.Here, we demonstrate a 3D self-rolled biosensor array (3D-SR-BA) integrated with a 3D cortical spheroid culture for simultaneousin vitroephys recording, functional Ca²⁺imaging, while monitoring the effect of drugs. We have also developed a signal processing pipeline to detect neural firings with high spatiotemporal resolution from the ephys recordings based on established spike sorting methods.Main results.The 3D-SR-BAs cortical spheroid interface provides a stable, high sensitivity recording of neural action potentials (<50µV peak-to-peak amplitude). The 3D-SR-BA is demonstrated as a potential drug screening platform through the investigation of the neural response to the excitatory neurotransmitter glutamate. Upon addition of glutamate, the neural firing rates increased notably corresponding well with the functional Ca²⁺imaging.Significance.Our entire system, including the 3D-SR-BA integrated with neuronal spheroid culture, enables simultaneous ephys recording and functional Ca²⁺imaging with high spatiotemporal resolution in conjunction with chemical stimulation. We demonstrate a powerful toolset for future studies of tissue development, disease progression, and drug testing and screening, especially when combined with native spheroid cultures directly extracted from humans.