Hybrid hydrogels assembled from synthetic polymers and coiled-coil proteindomains

Stimuli-sensitive polymer hydrogels, which swell or shrink in response to c hanges in the environmental conditions, have been extensively investigated and used as 'smart' biomaterials and drug-delivery systems(1,2). Most of th ese responsive hydrogels are prepared from a limited number of synthetic po lymers and their derivatives, such as copolymers of (meth)acrylic acid, acr ylamide and N-isopropyl acrylamide(3-12). Water-soluble synthetic polymers have also been crosslinked with molecules of biological origin, such as oli gopeptides(13) and oligodeoxyribonudeotides(14), or with intact native prot eins(15). Very often there are several factors influencing the relationship between structure and properties in these systems, making it difficult to engineer hydrogels with specified responses to particular stimuli. Here we report a hybrid hydrogel system assembled from water-soluble synthetic poly mers and a well-defined protein-folding motif, the coiled coil. These hydro gels undergo temperature-induced collapse owing to the cooperative conforma tional transition of the coiled-coil protein domain. This system shows that well-characterized water-soluble synthetic polymers can be combined with w ell-defined folding motifs of proteins in hydrogels with engineered volume- change properties(16,17).