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Bioinformatics of the Brain

FIGURE 3.3

Summary of the most common GBM (hetero)spheroid formation techniques.

A. Hanging drop, B. Low attachment wells, C. Agitation-based systems, D.

Magnetic systems, E. Scaffolds, F. Microfluidic systems.

of spheroids in one drop [144, 145]. Other two main methods to prevent cell-

surface binding, thus, forcing cell-cell adherence and the growth of spheroids in

suspension are low attachment surfaces and agitation-based strategies. In low

attachment surfaces (Figure 3.3B), treatment with polymers such as agarose

or commercially available ultra-low attachment well plate systems are com-

monly utilized. In these systems, shaking can serve as an external factor to

facilitate spontaneous spheroid manufacture. Homogenous size distribution of

spheroids in each round/flat bottom well with high viability can be achieved

with this method [146–149], but the application of this system on non-coated

surfaces such as petri dishes results in a wide range of size distribution of

spheroids and low throughput [150]. Agitation based strategies such as shak-

ers and rotating wall-based NASA HARV bioreactor system harness the ca-

pability of continuous stirring to prevent cell adhesion (Figure 3.3C). Thus,

single-cell suspension is restricted to cell-cell adhesion resulting in aggregation

and spheroid formation. Although large-scale production and ease of access

to spheroid are advantageous, requirement of the specialized equipment, het-

erogeneity of spheroid size and shape, and risk of cell disruption due to shear

during stirring create complications when this method is applied [142, 151]. In

another strategy, magnetic levitation (Figure 3.3D) uses magnetized cells and,

gravity is overcome by magnetic force mostly located at the top of the cells.

Magnetic systems/agents such as iron oxide can be applied to serve this pur-

pose [152, 153]. Although fast spheroid formation is obtained in this method,