Using Peptide Hetero-assembly to Trigger Physical Gelation and Cell Encapsulation

Stem cell transplantation holds tremendous potential for the treatment of various trauma and diseases. However, the therapeutic efficacy is often limited by poor and unpredictable post-transplantation cell survival. While hydrogels are thought to be ideal scaffolds, the sol-gel phase transitions required for cell encapsulation within commercially available biomatrices such as collagen and Matrigel often rely on non-physiological environmental triggers (e.g., pH and temperature shifts), which are detrimental to cells. To address this limitation, we have designed a novel class of protein biomaterials: Mixing-Induced Two-Component Hydrogels (MITCH) that are recombinantly engineered to undergo gelation by hetero-assembly upon mixing at constant physiological conditions, thereby enabling simple, biocompatible cell encapsulation and transplantation protocols. Building upon bio-mimicry and precise molecular-level design principles, the resulting hydrogels have tunable viscoelasticity consistent with simple polymer physics considerations. MITCH are reproducible across cell-culture systems, supporting growth of human endothelial cells, rat mesenchymal stem cells, rat neural stem cells, and human adipose-derived stem cells. Additionally, MITCH promote the differentiation of neural progenitors into neuronal phenotypes, which adopt a 3D-branched morphology within the hydrogels.