Engineering-Aligned 3D Neural Circuit in Microfluidic Device

The brain is one of the most important and complex organs in the human body. Although various neural network models have been proposed for in vitro 3D neuronal networks, it has been difficult to mimic functional and structural complexity of the in vitro neural circuit. Here, a microfluidic model of a simplified 3D neural circuit is reported. First, the microfluidic device is filled with Matrigel and continuous flow is delivered across the device during gelation. The fluidic flow aligns the extracellular matrix (ECM) components along the flow direction. Following the alignment of ECM fibers, neurites of primary rat cortical neurons are grown into the Matrigel at the average speed of 250 μm d^-1 and form axon bundles approximately 1500 μm in length at 6 days in vitro (DIV). Additionally, neural networks are developed from presynaptic to postsynaptic neurons at 14 DIV. The establishment of aligned 3D neural circuits is confirmed with the immunostaining of PSD-95 and synaptophysin and the observation of calcium signal transmission. A novel microfluidic platform for formation of 3D neural circuit is reported. Microfluidic channels are filled with Matrigel and hydrostatic pressure is maintained across the width of the gel during cross-linking. This generates aligned extracellular matrix (ECM) structures in the Matrigel to guide the axon growth direction. Compared to neurons cultured in randomly cross-linked Matrigel, axon bundles that connect pre-/post-synaptic neurons can be formed.