Figure 2.

2D neuronal network topologies obtained with network engineering techniques. (A) Schematic diagrams of different network topologies obtained with and without the use of network engineering techniques. Uniform random cultures are made of uniformly distributed neurons connecting in a random network architecture, i.e., without a preferential site of adhesion, directionality or connectivity. Uniform neuronal networks with an imposed topology can be obtained via bio-printing and patterning techniques, dictating the site of cell adhesion as well as the path of neuronal processes outgrowth. In vitro modular neuronal network models can also be defined by two or more random modules, where the connectivity between/among modules is the sole topology parameter controlled by the bioengineering strategy. (B) Microscopy image of a uniform random culture of primary hippocampal neurons at 21 days in vitro. Scale bar: 100 µm. Adapted with permission from [26]. Copyright © 2014 Elsevier B.V. (C) Fluorescence microscopy image of a uniform grid engineered neuronal network obtained with combined micro-contact printing of an adhesion promoter and coating of a repulsive (agarose) layer. Scale bar: 200 µm. Adapted with permission from [31]. (D) Multi-modular primary neuronal networks obtained with poly-dimethylsiloxan (PDMS) mask-guided bioprinting, showing inter-module connections. Adapted with permission from [42]. (E) Engineered interconnected neuronal microcircuits matching the spatial distribution of microelectrodes within an electrode array. The microcircuits were obtained by directional geometric guidance provided by PDMS microstructures. Scale bar: 200 µm. Adapted with permission from [33].