REVERSIBLE HYDROGELS FROM SELF-ASSEMBLING ARTIFICIAL PROTEINS

Recombinant DNA methods were used to create artificial proteins that u ndergo reversible gelation in response to changes in pH or temperature . The proteins consist of terminal Leucine zipper domains flanking a c entral, flexible, water-soluble polyelectrolyte segment. Formation of coiled-coil aggregates of the terminal domains in near-neutral aqueous solutions triggers formation of a three-dimensional polymer network, with the polyelectrolyte segment retaining solvent and preventing prec ipitation of the chain. Dissociation of the coiled-coil aggregates thr ough elevation of pH or temperature causes dissolution of the gel and a return to the viscous behavior that is characteristic of polymer sol utions. The mild conditions under which gel formation can be controlle d (near-neutral pH and near-ambient temperature) suggest that these ma terials have potential in bioengineering applications requiring encaps ulation or controlled release of molecular and cellular species.