Engineering Tunable Elastin-Like Polypeptide/Poly(ethylene glycol) Diacrylate Composite Hydrogels for Injectable Soft Tissue Fillers

Soft tissue augmentation is widely used for cosmetic and reconstructive indications, requiring void filler materials that can be delivered minimally invasively while maintaining structural stability and tissue-like mechanics. Here, we engineered a biocompatible, injectable composite hydrogel based on elastin-like polypeptides (ELPs) and poly (ethylene glycol) diacrylate (PEGDA) with tunable viscoelasticity, favorable mechanical properties, and high structural integrity for soft tissue reconstruction. Hydrogels were formed by photoinitiated crosslinking involving thiol–ene coupling between cysteine thiols on ELP and acrylate groups of PEGDA, yielding rapid in situ gelation. The ELP component provided elastin-like extensibility, while PEGDA contributed resilient elastic recovery with low energy dissipation under cyclic loading. By modulating the PEGDA/ELP ratio, the composite viscoelastic response could be tuned, enabling mechanical performance that exceeded either polymer network alone and producing soft tissue–like elastic moduli. Notably, the ELP/PEGDA (50/50) formulation achieved >300% elongation, minimal permanent deformation (~3.5%), and low energy loss (~15%), comparable to native elastin, supporting its potential as an injectable void filler for soft tissue reconstruction.