Table 1.

Major liquid-based spheroid culture approaches

Spheroid forming technique	Advantages	Disadvantages
Rotary vessel/spinner flask	- Large number of spheroids - Convenient culture and harvesting	- Non-uniformly sized spheroids - Incompatible with high-throughput screening - Incompatible with defined heterotypic culture conditions
Hanging drop array	- Uniformly sized spheroids - One spheroid per drop - High throughput - Compatible with robotics - Compatible with heterotypic cultures	- Difficult to handle cultures - Need for custom plates - Incompatible with plate readers - Lack of temporal control
Liquid overlay microplate Aqueous two-phase system (ATPS) Microfabricated microwell array	- Convenient culture and harvesting - High throughput - Compatible with robotics - Compatible with plate readers - Uniformly sized spheroids - One spheroid per well - High throughput - Compatible with robotics - Compatible with heterotypic cultures - Compatible with plate readers - Temporal control - Uniformly sized spheroids - One spheroid per well - High throughput	- Variations in size of spheroids - May give more than one spheroid per well - Need to optimize consistency of liquid handling dispensing of sub-microliter volumes - Need for microfabrication - Incompatible with robotics - Incompatible with plate readers - Exposes all spheroids to a single treatment condition - Lack of temporal control