Our findings are relevant to the design of future screening protocols using 3D spheroids compared to 2D neuronal cultures. 3D neuronal culture has a number of advantages and disadvantages compared to 2D neuronal culture. The first disadvantage of 3D neurons is the reduced diffusion of candidate drugs. Even across the tiny (10 um) distance between the peripheral and internal regions of iPSC-derived neuro-spheroids, differences in concentration exist. Identifying diffusion-limiting factors of 3D neuronal cultures may help to advance diverse areas of neurotherapeutics and the consistency needed for drug screening. Chronic dosing may represent a second disadvantage to high throughput screening using 3D cultures. The increased time requirement for uniform bioavailability within the 3D spheroids indicates that additional development is needed before this approach is ready for large-scale drug screening.
