Physical hydrogels photo-cross-linked from self-assembled macromers for potential use in tissue engineering.

To engineer artificial extracellular matrices (ECMs) enabling degradation-independent cell migration that mimicked nonproteolytic cell migration through physically stabilized ECMs in biological systems, polymers having a hydrophilic chain flanked by a terminal self-assembling leucine zipper domain and a terminal photoreactive acrylate group were molecularly engineered to form photo-cross-linkable physical hydrogels. Physical association of the leucine zippers resulted in multifunctional macromers, which were photo-cross-linkable into hydrogels. Gel formation was confirmed by rheological measurements. The physical nature of the hydrogel networks was shown by hydrogel disassembly in denaturing solutions that disrupted the secondary structure of the leucine zippers. Outgrowth of encapsulated fibroblast aggregates was observed in these physical hydrogels but not observed in a control hydrogel in which leucine zippers were covalently linked. The collective properties of these hydrogels, including the physical nature, the photo-cross-linkable characteristic, and the flexibility for systematic engineering of material properties, will provide unique opportunities for tissue engineering.