Mechanical properties of biological gels

The rheological properties of biological gels are illustrated by reviewing measurements made on samples containing polymer networks reconstituted from cytoskeletal constitutents. Although these networks are crosslinked by non-covalent interactions which may lead to transient gel behavior, the early-time (rapid) mechanical response of the gels can be characterized by the instantaneous shear modulus. A theory for the latter is described, and used to examine the relationship between the cortical f-actin content and the stiffening of activated polymorphonuclear leukocytes.