Fabrication of a shape memory hydrogel based on imidazole-zinc ion coordination for potential cell-encapsulating tubular scaffold application

A dipole-dipole reinforced copolymer hydrogel was synthesized by the one-step photopolymerization of vinylimidazole (VI) and acrylonitrile (AN) comonomer in the presence of a polyethylene glycol-based crosslinker. The mechanical properties of PVI-AN gels were tremendously increased by only chelating several mmol L-1 zinc ions, which was shown to firmly lock the temporary shape of the gel. Extraction of zinc ions by a complexing agent could facilitate the recovery of a permanent shape, and the memory behavior was reversible. The PVI-AN hydrogels supported the growth of L929 cells. The cell-seeded flat hydrogel sheet was folded into a temporary tubular scaffold and fixed in a culture medium containing 5 mmol L-1 zinc ions. After unfolding the tube, the exposed L929 cells were shown to adhere well on the surface of the gel. It is anticipated that this cell-loaded SM hydrogel could be fixed to a desired shape in vitro by small numbers of zinc ions for a potential implantable tissue engineering scaffold.