Table 2.

Advantages and disadvantages of 2D cells versus 3D organoids

Model system	Advantages	Disadvantages
3D brain organoids	3D condition is as in vivo growth environment.	Insufficient supply of nutrition and oxygen in the core area following long-term culture.
	Multiple types of cells to reflect the interactions including glia-neurons, neuron-neurons, etc.	Uncontrollable variations owing to the different genetic backgrounds of the donors.
	Patient-derived iPSCs to show more information on the disease phenotypes and mechanisms.	Relatively costly in time and money compared with 2D cell lines.
2D cell lines or primary neurons	Simple culture system with controllable conditions for high-throughput screening.	Lacking 3D growth condition.
	Obvious phenotypes to be detected for reflecting the drug bioactivity.	Cannot reflect the physiological condition compared with human cells.
2D iPSC-derived neurons	Functional neurons derived from patient-specific iPSCs.	Lacking 3D growth condition.
	Detectable phenotypes with 2D level to show drug bioactivity.	Lacking multiple cell interactions as the in vivo condition.
		Relatively costly in time and money compared with 2D cell lines.

2D: Two-dimensional; 3D: three-dimensional; iPSC: induced pluripotent stem cell.