Danny Alge showed hydrogels could be formed using the bioorthogonal tetrazine-norbornene reaction. The synthetic accessibility of these chemistries will open new doors for the design of cell instructive materials.
D.A. Alge, M.A. Azagarsamy, D.F. Donohue, and K.S. Anseth, "Synthetically Tractable Click Hydrogels for Three-Dimensional Cell Culture Formed Using Tetrazine-Norbornene Chemistry," Biomacromolecules (2013).