In situ forming physical hydrogels for three-dimensional tissue morphogenesis.

In situ forming physical hydrogels are formed through a biologically benign reaction between two multi-arm macromers, one containing terminal thiol and the other containing terminal vinyl sulfone groups. One macromer is self-assembled through a coiled-coil domain; and the physical junction of this macromer confers the physical nature to the whole network. Unlike covalently cross-linked hydrogels in which material degradation is a prerequisite for three-dimensional cell movement, these physical hydrogels have junctions that undergo reversible dissociation and re-association, constitutively opening paths for cell movement. Epithelial cells encapsulated in these hydrogels can form hollow spherical cysts without the need for material degradation.