A neuronal wiring platform through microridges for rationally engineered neural circuits.

Yu Wu,Huiran Yang,Ruili Xie,Yong Wang,Meijian Wang,Liang Guo,Benjamin J Seicol,Hao Qi

doi:10.1063/5.0025921

Abstract

Precisely engineered neuronal circuits are promising for both fundamental research and clinical applications. However, randomly plating thousands of cells during neural network fabrication remains a major technical obstacle, which often results in a loss of tracking in neurons' identities. In this work, we demonstrated an accurate and unique neural wiring technique, mimicking neurons' natural affinity to microfibers. SU-8 microridges, imitating lie-down microfibers, were photolithographically patterned and then selectively coated with poly-l-lysine. We accurately plated Aplysia californica neurons onto designated locations. Plated neurons were immobilized by circular microfences. Furthermore, neurites regrew effectively along the microridges in vitro and reached adjacent neurons without undesirable crosstalks. Functional chemical synapses also formed between accurately wired neurons, enabling two-way transmission of electrical signals. Finally, we fabricated microridges on a microelectrode array. Neuronal spikes, stimulation-evoked synaptic activity, and putative synaptic adaption between connected neurons were observed. This biomimetic platform is simple to fabricate and effective with neurite pathfinding. Therefore, it can serve as a powerful tool for fabricating neuronal circuits with rational design, organized cellular communications, and fast prototyping.

Highlights

Composed of hundreds[1] to billions[2] of wired neurons, the nervous system controls the most sophisticated functions in animals, such as movement, memory, and cognition
Single-cell resolution could be achieved with extracellular matrix (ECM) protein patterning[23] and poly-l-lysine (PLL) surface patterning,[24] plating thousands of neurons all together and letting cells randomly attach to predefined adhesion spots often result in a neuronal network with unknown identities of each cell, failing to produce a rationally and accurately defined neuronal circuit
Fabrication of SU-8 microstructures had been well developed, and it could be integrated with many microelectronic devices, such as microelectrode arrays (MEAs) for neural recording and stimulation

Summary

Introduction

Composed of hundreds[1] to billions[2] of wired neurons, the nervous system controls the most sophisticated functions in animals, such as movement, memory, and cognition. Similar to electronic circuits in many ways, functional circuits composed of living neurons are still in their early exploration.[3,4] Fabrication of such neurobiological circuits requires both micropatterning of individual neurons and accurate guidance of their neurites. On the other hand, micromachining enables the fabrication of topographically defined culture environments in order to physically restrict and trap neurons or guide neurite regrowth. Trapping cells in microwells[37] and guiding their axons through microchannels are problematic. It often ends up with either a low degree of neurite polarity due to large channel dimensions or uncontrolled growth cones that migrate out of the channels. It is difficult to integrate 3D constructs with electrophysiology tools, such as microelectrode arrays (MEAs), to monitor and intervene neural activity

Methods

Results

Discussion

Conclusion