Biosafe macromolecular crosslinking enables tunable biodegradation and sustained reparative bioactivity of small intestinal submucosa.

Decellularized extracellular matrix scaffolds such as porcine small intestinal submucosa (SIS) provide native-like structure and bioactive cues for tissue repair, yet their premature and poorly controlled biodegradation compromises mechanical support and limits durable regeneration. Existing stabilization strategies rely on small-molecule crosslinkers or multi-step chemistries that raise concerns regarding cytotoxicity, residual reactivity, and matrix alterations that hinder constructive host integration. Here, we address this limitation by stabilizing SIS using a biosafe macromolecular crosslinker, o-phthalaldehyde-terminated four-armed poly(ethylene glycol) (4aPEG-OPA), which undergoes rapid and efficient condensation with primary amines in collagen to form stable covalent linkages. This approach enables delayed and tunable biodegradation while preserving the intrinsic biological and physicochemical features of SIS. The resulting SIS-PEG scaffolds maintain tensile strength comparable to native SIS and exhibit improved mechanical retention during degradation. With mild crosslinking, SIS-PEG remains cytocompatible, supports cell adhesion, and enhances fibroblast-mediated collagen deposition, and promoting effective tissue repair, angiogenesis, and M2 macrophage polarization in vivo. This strategy provides a practical and generalizable route to balance biodegradation and function in SIS and other amine-rich biomaterials.