Bioelectrical interfaces with cortical spheroids in three-dimensions

Abstract

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 activity across the entire native 3D geometry of the cellular construct. Here, we demonstrate a 3D self-rolled biosensor array (3D-SR-BA) integrated with a 3D cortical spheroid culture for simultaneous in-vitro electrophysiology recording, functional Ca 2+ imaging, and drug effect monitoring. We have also developed a signal processing pipeline to detect neural firings with high spatiotemporal resolution from the electrophysiology recordings based on established spike sorting methods. The 3D-SR-BAs cortical spheroid interface provides a stable, high sensitivity recording of neural action potentials (< 50 µV 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 neuronal firing rates increased notably corresponding well with the functional Ca 2+ imaging. Our entire system, including the 3D-SR-BA integrated with neural spheroid culture, enables simultaneous electrophysiology recording and functional Ca 2+ 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.

Shell Microelectrode Arrays (MEAs) for brain organoids

“…We further confirm that the signal recorded is from the brain organoids by examining the response to 20 μM glutamate neurotransmitter added to the culture medium served as a positive control for the spontaneous recording (23,37). The spike signal-to-noise ratio (SNR) before and after the glutamate application showed statistically significant amplification (median increased by 57.6%) on the amplitude of firing spikes (Fig.…”

“…Kalmykov et al . have developed a cylindrical sensor array for cardiac and cortical organoids ( 21, 23 ). This methodology requires manual unrolling of the cylinder with a micromanipulator to enclose the organoids which can limit throughput and also has a limited cylindrical shape.…”

“…While several modifications such as spine-shaped electrodes, nanowires, and 3D nanostructures have been patterned on these MEA plates to increase the signal, the recording contact area is still limited to the bottom of the organoid where it is attached to the plate (16)(17)(18)(19). Recently, several curved and folded shapes have been introduced for MEA recording, including buckled, cylindrical, and shells (20)(21)(22)(23)(24)(25)(26). For example, Cools et al have previously utilized SiO/SiO2 bilayers to create a self-folding shell for single cardiac cell encapsulation but the dimensions and rigid material composition of such single cell devices may not suitable for brain organoids (20).…”

“…For example, Cools et al have previously utilized SiO/SiO2 bilayers to create a self-folding shell for single cardiac cell encapsulation but the dimensions and rigid material composition of such single cell devices may not suitable for brain organoids (20). Kalmykov et al have developed a cylindrical sensor array for cardiac and cortical organoids (21,23). This methodology requires manual unrolling of the cylinder with a micromanipulator to enclose the organoids which can limit throughput and also has a limited cylindrical shape.…”

Transparent and Conformal Microcoil Arrays for Spatially Selective Neuronal Activation

“…For example, work by Kim et al (2011) and Zhang et al (2013) (Kim et al, 2011;Zhang et al, 2013) have demonstrated that serpentine electrode interconnects incorporated within ultra-thin substrate materials can form extremely stretchable interfaces that can conform to different types of biological tissue, with modulus of elasticity that can range between 100 MPa to 300 kPa. Additionally, devices embedded in SU-8 have also achieved electrophysiological interfaces using complex 3D geometries (e.g, self-rolled spheroids) (Kalmykov et al, 2021).…”