Ultrafast gelation of multifunctional hydrogel/composite based on self-catalytic Fe3+/Tannic acid-cellulose nanofibers

Multifunctional hydrogels with transparency, ultraviolet (UV)-blocking, stretchable, self-healing, adhesive, antioxidant and antibacterial properties are promising materials for biomedical and relevant applications. However, preparation of these hydrogels at ambient environment without stimuli is still a challenge. Here, a series of hydrogels possessing ultrashort gelation time (~30 s) at room or cold temperature were fabricated based on self-catalytic Fe3+/Tannic acid-cellulose nanofiber (Fe3+/TA-CNF). Fe3+/TA-CNF formed stable redox pairs to activate ammonium persulfate (initiator), generating abundant free radicals to trigger the ultrafast polymerization of acrylic acid (AA). To improve the antibacterial ability of hydrogel, a bilayer hydrogel composite (NF@HG) composed of tetracycline hydrochloride (TH)-loaded electrospun nanofibers and hydrogel layer was fabricated via a mild casting method. The NF@HG exhibited enhanced antibacterial ability and the sustained release of TH can provide long-term antibacterial activity. Besides, cell viability results demonstrated that NF@HG was non-cytotoxic. Taken together, this strategy based on self-catalytic Fe3+/TA-CNF system may inspire new aspects on fast and economical preparation of multifunctional hydrogels or composites, which have attractive industrial applications for biomedical materials.