Rapid generation of functional engineered 3D human neuronal assemblies: network dynamics evaluated by micro-electrodes arrays

In this work we adapted a protocol for the fast generation of human neurons to build 3D neuronal networks with controlled structure and cell composition suitable for systematic electrophysiological investigations. We used biocompatible chitosan microbeads as scaffold to build 3D networks and to ensure nutrients-medium exchange from the core of the structure to the external environment. We used excitatory neurons derived from human-induced pluripotent stem cells (hiPSCs) co-cultured with astrocytes. By adapting the well-established NgN2 differentiation protocol, we obtained 3D engineered networks with good control over cell density, volume and cell composition. We coupled the 3D neuronal networks to 60-channel micro electrode arrays (MEAs) to monitor and characterize their electrophysiological development. In parallel, we generated two-dimensional neuronal networks cultured on chitosan to compare the results of the two models. We sustained samples until 60 d (DIV) and 3D cultures were healthy and functional. From the structural point of view, the hiPSC derived neurons were able to adhere to chitosan microbeads and to form a stable 3D assembly thanks to the connections among cells. From a functional point of view, neuronal networks showed spontaneous activity after a couple of weeks. We presented a particular method to generate 3D engineered cultures for the first time with human-derived neurons coupled to MEAs, overcoming some of the limitations related to 2D and 3D neuronal networks and thus increasing the therapeutic target potential of these models for biomedical applications.