Hydrogels can be physically or chemically crosslinked. Inter alia, chemical crosslinking can be achieved by UV or reactive functional groups or enzymatic crosslinking . However, photo-polymerization requires a photo-sensitizer/initiator and relatively high-energy irradiation. Crosslinking with various commercially available crosslinkers can lead to cytotoxic effects , alternatively specific biological triggers can be utilized . Alternative crosslinking methods remain to be sought after.