Subtle Regulation of Scaffold Stiffness for the Optimized Control of Cell Behavior

Abstract

The rigidity of extracellular matrices can impact cell fate, guide tissue development, and initiate tumor formation. Scaffolds such as hydrogels with tunable levels of stiffness have been developed to control cell adhesion, migration, and differentiation, providing suitable microenvironments for different tissue outcomes. However, studies of cell−material interactions are largely confined to biomaterials with stiffness values that are coarsely regulated, so refinements in sensitive cellular responses and optimal stiffness values that determine cell fate remain elusive. Here, a freezing temperature, as a tunable regulating factor, was introduced to freeze-drying processes to form silk fibroin (SF) scaffolds with refined control of stiffness values. Due to this control of intermediate structural conformations of SF, the scaffolds exhibited differences in stiffness values to permit refined assessments of impact on cell behavior on cell-friendly surfaces. Both in vitro and in vivo results with these scaffolds exhibited gradually changeable cell migration and differentiation outcomes, as well as differences in tissue ingrowth, demonstrating the sensitivity of cellular responses to such refined mechanical cues. The optimal vascularization capacity of these SF scaffolds was in the 3−7.4 kPa range, suggesting a key range to develop bioactive biomaterials. Systematic fine regulation of scaffold rigidity based on the present strategy provides a platform for an improved understanding of cell−material interactions and also for generating optimized microenvironments for tissue regeneration.

Anisotropic silk nanofiber layers as regulators of angiogenesis for optimized bone regeneration

“…The SFN layers slowed the release of DFO and there was significantly improved cell proliferation in the DFO-laden scaffolds with the slower DFO release rate. Besides better cytocompatibility, the aligned SFN layers induced the directional migration of HUVECs, which would also facilitate the cell infiltration and tissue ingrowth [ 28 , 36 ]. At day 3, significant migration was found for the cells cultured on the scaffolds with the aligned layers, while little migration occurred for cells cultured on the SF/HA-R and SF/HA-DFO-R scaffolds ( Fig.…”

“…To assess cell migration behavior, HUVECs (2 ​× ​10 6 /scaffold) were seeded at the scaffold centers [ 36 ]. At specified times, all scaffolds were fixed and stained for observation using CLSM.…”

The Materiobiology of Silk: Exploring the Biophysical Influence of Silk Biomaterials on Directing Cellular Behaviors

“…A plausible explanation for this behavior may be the imbalance between cell traction forces and corresponding ECM response, a crucial parameter for assembly of cell-matrix complexes and cell spreading. For instance, a study reported that the fine tuning of silk scaffold’s stiffness induces different endothelial migration and aggregation ( Lu et al, 2019 ), suggesting a sensitive dependence of cell migration on mechanical cues.…”

Electric field-driven building blocks for introducing multiple gradients to hydrogels

“…Recently, beta-sheet rich SF nanofibers (BSNF) were assembled in aqueous solutions in our group, exhibiting superior biocompatibility and loading drug capacity to previous SF materials (Lu et al, 2011;Wu et al, 2016). BSNF as reinforcing nanofibers could be introduced to different hydrogels and scaffolds to tune the mechanical cues finely, resulting in controllable differentiation behaviors of stem cells Lu et al, 2019). Different cargos such as small molecules, growth factors, graphene sheets and gold nanoparticles were loaded on the nanofibers, which provided tunable physical and biochemical cues for cells and tissues (Ding et al, 2016b;Wu et al, 2016;Zhang et al, 2018;Xu et al, 2019).…”