Engineering Human Brain Assembloids by Microfluidics.

Brain assembloids offer a highly promising strategy to model human brain development and disease, and advance potential studies in regenerative medicine, therapeutic screening and drug discovery, while it is challenging to produce uniform brain organoids and assemble them flexibly by conventional methods. Here, we present a multidisciplinary engineered strategy to generate human brain assembloids with desired patterning based on microfluidic technology. By encapsulating human induced pluripotent stem cells in microcapsules via microfluidic electrospray, brain region-specific organoids are efficiently formed, which are then introduced into a microfluidic chip consisting of a bottom layer with a micropillar array and a movable upper layer with a complementary microhole array. These brain organoids can settle into microholes and fuse into brain assembloids. As varied organoid microcapsules with designed 1D sequences or 2D arrays could be assembled into the vertical microholes, large coding amounts of fused brain assembloids with desired patterning could be produced. We have found that brain assembloids composed of cortical, hippocampal, and thalamic organoids could grow and function well, characterized with active neural migration and interaction. These features indicated that the suggested flexible, scalable and controlled microfluidic systems are remarkably potential in wide applications of brain assembloids in neurological and biomedical fields. This article is protected by copyright. All rights reserved.