Chlorophyll as a sustainable crosslinking strategy for engineering highly compressible hydrogels

Hydrogels are promising candidates for tissue repair. Non-invasive delivery of hydrogel patches involving high strains and deformations requires mechanical robustness and complex material design. Here we show chlorophyll, a sustainable plant-derived small molecule, functions as a universal physical crosslinker to significantly enhance hydrogels' compressibility and resilience. Chlorophylls self-assemble in aqueous pre-polymer solution via hydrophobic interactions, leading to the nano-aggregations, acting as physical crosslinkers and anchoring points within hydrogels' matrix. Additionally, the solvent exchange (SE) process promotes macroporous structure formation for high compressibility and resilience. With chlorophyll, the maximum compressive strains of gelatin methacrylate (GC) hydrogels increased from ~43% to ≥90%, allowing injection under 90.4% deformation while preserving structural integrity. This strategy enabled the fabrication of a single 36-mm diameter injectable conductive polypyrrole-deposited GC (GCP) cardiac patch for myocardial repair in minipigs. Moreover, chlorophyll functions as an intrinsic antioxidant reservoir, and improved ejection fraction (EF) by 11 % in porcine infarcted hearts.