Synthetically Tractable Click Hydrogels for Three-DimensionalCell Culture Formed Using Tetrazine–Norbornene Chemistry

摘要

The implementation of bio-orthogonal click chemistries is a topic of growing importance in the field of biomaterials, as it is enabling the development of increasingly complex hydrogel materials capable of providing dynamic, cell-instructive microenvironments. Here, we introduce the tetrazine–norbornene inverse electron demand Diels–Alder reaction as a new cross-linking chemistry for the formation of cell laden hydrogels. The fast reaction rate and irreversible nature of this click reaction allowed for hydrogel formation within minutes when a multifunctional PEG-tetrazine macromer was reacted with a dinorbornene peptide. In addition, the cytocompatibility of the polymerization led to high postencapsulation viability of human mesenchymal stem cells, and the specificity of the tetrazine–norbornene reaction was exploited for sequential modification of the network via thiol–ene photochemistry. These advantages, combined with the synthetic accessibility of the tetrazine molecule compared to other bio-orthogonal click reagents, make this cross-linking chemistryan interesting and powerful new tool for the development of cell-instructivehydrogels for tissue engineering applications.