Shape memory collagen scaffolds sustain large-scale cyclic loading

Natural biopolymer hydrogels often suffer from relatively low moduli and
an inability to maintain structure and mechanics under cyclic loading,
limiting their utility in dynamic mechanical environments. Here, a
crosslinked collagen cryogel scaffold was fabricated by mechanical
pre-compression to densify the network. Following lyophilization, the
porous scaffolds maintained sustained >90% axial compressive strain
with 200 cycles. Ogden hyperelastic modeling and second harmonic
generation (SHG) imaging revealed that fiber alignment, densification, and
strain-stiffening contributed to resilience under repetitive large-scale
loading. After rehydration, crosslinked and densified hydrogels showed
network stability and recoverability under cyclic loading, with a
significantly reduced phase transition strain compared to non-crosslinked
controls. The scaffolds supported cell encapsulation and maintained cell
viability after 50 cycles of 90% compressive strain. Cyclic loading
significantly densified the encapsulated cells in the loading direction,
comparable to non-loaded controls. Overall, these results suggest that
densified, shape memory collagen scaffolds provide a mechanically robust
and biocompatible system for dynamic mechanical environments.