Fig. 5.

The stiffness of cell sheets and spheroids relative to the stiffness of single cells, tissues, and some ECM molecules. The elastic moduli (E) are reported on the logarithmic scale. The cells generally have stiffness in the range from the tens of Pa (mucus, neural tissues) to the several hundreds of kPa, with the neurons among the softest cells and the muscle cells among the stiffest cells. The tissues span a larger range from the tens of Pa to the several GPa (Guimarães et al. 2020). Depicted from the softest to the stiffest: neural tissues, liver, lung, skin, muscle tissues, cartilage, tendon, and bone. Reported values of spheroid stiffness are close to such of single cells. Cell sheets show an elastic modulus close to cells with higher values up to the several MPa, generally associated with the multilayered structure and higher ECM content. The values of the ECM molecules (fibronectin, fibrin, elastin, collagen) are included for comparison