Fenton reaction-initiated formation of biocompatible injectable hydrogels for cell encapsulation

A chemical-crosslinked, biocompatible and injectable hydrogel was formed by Fenton reaction initiated polymerization. The gelation time of N-(2-hydroxyethyl)acrylamide and PEG-diacrylate, which are two representative monomers, was shown to be tunable from instant to 15 min at an H₂O₂ concentration below several mmol L^-1 in neutral medium. The strength of the hydrogel could be regulated by the concentration of the monomer and the Fenton's reagent. The hydrogels prepared by H₂O₂/Fe²⁺ initiation showed low cytotoxicity. The bone marrow mesenchymal stem cells and L929 cells encapsulated in the gels exhibited high viability even after 7 days of co-culture. Both the L929 cells encapsulated in situ into the hydrogels and those co-cultured with the hydrogel showed negligible cell death and apoptosis. It is anticipated that the familiar Fenton reaction may act as a new initiator system to fabricate biocompatible injectable hydrogels.