What are the scaffold-free methods of growing 3D cell cultures?

Scaffold-free methods of growing 3D cell cultures allow the cells to self-assemble to form non-adherent cell aggregates called spheroids.

There are three scaffold-free methods: 

1- The forced-floating method – This technique uses low adhesion well-plates that are polymer coated. After centrifugation, the well-plates are filled with a cell suspension to create spheroids.

2- The hanging drop method – In this scaffold-free technique, a cell suspension aliquot is placed inside a MicroWell MiniTray. When the plates (trays) are inverted, aliquots become droplets presenting cell aggregates on their tips, thus creating compact and homogenous spheroids.

3- The agitation-based method – This technique generates three-dimensional spheroids using a rotating bioreactor into which a cell suspension is placed. The cell suspension gradually converts isolated cells into cell aggregates. The continuous stirring prevents the aggregates from adhering to the container wall, eventually generating a wide range of non-uniform spheroids instead.

Spheroids obtained using non-scaffolding methods are generally smaller in size and less resistant.