Taken together, these results demonstrate that metal-phenolic supramolecular gelation occurs in vivo, and provide essential in vivo characterization for this emerging class of materials. The in vivo response is largely comparable with conventional calcium-alginate gels. Additional benefits of the TiTannic system, including readily tuneable gelation time, robustness and adaptability, and the easy, low-cost, off-the-shelf, and scalable preparation process, make this new class of material of significant interest for diverse biomedical applications.