Self‐Folding Graphene‐Based Interface for Brain‐Like Modular 3D Tissue

Abstract

Electrophysiology of 3D neuronal cultures is of rapidly growing importance for revealing cellular communications associated with neurodevelopment and neurological diseases in their brain‐like 3D environment. Despite that the brain also exhibits an inherent modular architecture that is essential for cortical processing, it remains challenging to interface a modular network consisting of multiple 3D neuronal tissues. Here, a self‐folding graphene‐based electrode array is proposed that enables to reconstruct modular 3D neuronal tissue and investigate firing dynamics among moduli. A graphene‐sandwiched parylene‐C film self‐folds into a cylindrical structure within which living cells can be encapsulated. Culture of encapsulated cells inside the folded graphene enables to spontaneously construct 3D cell aggregates and ensure firm contact between the graphene surface and encapsulated cells. As the inner graphene surface can be utilized as an electrode, the reliable cell–electrode contact allows for long‐term electrical recording from multiple 3D aggregates. Additionally, the modular network consisting of multiple 3D aggregates exhibits richer firing patterns than a conventional homogenous 2D network, which demonstrates that the approach enables measurements of firing dynamics in complex 3D neuronal networks. The deformable graphene electrode will be a powerful platform for investigating complex cellular communications in brain‐like 3D cultures.

Small-artery-mimicking multi-layered 3D co-culture in a self-folding porous graphene-based film

“…1A). As described in previous studies, 15,16,24 the dissolution of the sacrificial Ca-alginate layer releases a bilayer of graphene and parylene-C, and an internal residual stress within the bilayer induces the bending. The composition of the bilayer is also maintained after self-folding, as confirmed by Raman spectroscopy.…”

“…The composition of the bilayer is also maintained after self-folding, as confirmed by Raman spectroscopy. 15,16,24 Additionally, no clear defects were observed in the folded graphene. Thus, both materials can work as cell-scaffolds on the outer and inner surfaces of the micro-roll.…”

“…Self-folding materials and devices have been utilized as cell scaffolds with precise curved geometries. 9–16 A predetermined internal stress gradient inside a nanometre-thick film drives self-folding and forms a micro-scale cylindrical structure (micro-roll). By selecting biocompatible film materials, living vascular cells can be grown on the curved surface, and they form a cylindrical or tubular tissue.…”

“…20–22 In fact, we have previously developed a graphene-based self-folding porous film and proved that micro-scale pores across the nanometre-thick film enable neurons inside the micro-roll to communicate with the surrounding neurons. 15,16 Both graphene and parylene-C, which were used as the inner and outer surfaces of the micro-roll, work as suitable cell scaffolds due to their excellent biocompatibility and transparency. Thus, the separated co-culture on the self-folding porous film will emulate the characteristics of small arteries, including micro-scale geometry, cellular composition, and ECM structure.…”