Shape Memory Silk Protein Sponges for Minimally Invasive Tissue Regeneration

Abstract

Porous silk protein scaffolds were designed to display shape memory characteristics and volumetric recovery following compression. Two strategies were utilized to realize shape recovery: the addition of hygroscopic plasticizers like glycerol and tyrosine modifications with hydrophilic sulfonic acid chemistries. Silk sponges were evaluated for recovery following 80% compressive strain, total porosity and pore size distribution, secondary structure development, in vivo volume retention, cell infiltration, and inflammatory responses. Glycerol-modified sponges recovered up to 98.3% of their original dimensions following compression, while sulfonic acid / glycerol modified sponges swelled in water up to 71 times their compressed volume, well in excess of their original size. Longer silk extraction times (giving lower silk molecular weights) and higher concentrations of glycerol gave sponges with greater flexibility and shape fidelity, with no loss in modulus following compression. Sponges were over 95% porous, with secondary structure analysis indicating glycerol-induced β-sheet physical crosslinking. Tyrosine modifications with sulfonic acid interfered with β-sheet formation. Glycerol-modified sponges exhibited improved rates of cellular infiltration at subcutaneous implant sites with minimal immune response in mice. They also degraded more rapidly than unmodified sponges, a result posited to be cell-mediated. Overall, this work suggests that silk sponge systems may be useful for minimally invasive deployment in soft tissue augmentation procedures.

Engineering the Future of Silk Materials through Advanced Manufacturing

“…The modification and functionalization are also achievable at multiple levels ranging from genetic engineering and chemical modification to mesoscale assembly and macroscale mixing. Additionally, silk proteins can be readily formed into a variety of material formats ranging from gels, strands, sponges, and blocks, through to foams and films . It offers unlimited opportunities on the creation of multifunctional, hierarchical, and heterogeneous structures and devices at multiple scales over orders of magnitudes—ranging from nm to mm and above—with shape and function on demand.…”

Self‐Healing Silk Fibroin‐Based Hydrogel for Bone Regeneration: Dynamic Metal‐Ligand Self‐Assembly Approach

“…Indeed, the self-healing SF-based (i.e., Am-HA-BP·CaP@mSF) hydrogel could be injected readily and molded to any shape (Figure 5a; Movie S1, Supporting Information). [55] Most importantly, the preparation of such materials is not compatible with encapsulation of sensitive biomacromolecules or cells. However, these elastomeric materials either require nonphysiological conditions for their shape recovery (such as high temperature of 70 °C) [54] or the volumetric expansion of the compressed silk sponge is essentially isotropic and hence cannot fill complex defects with irregular shapes.…”

Water‐insoluble amorphous silk fibroin scaffolds from aqueous solutions

“…Various studies have addressed this issue, such as by adjusting RSF fabrication processes (Bai et al, ; Brown et al, ; Dong, Zhao, Xiao, Lu, & Kaplan, ; Rnjak‐Kovacina et al, ; Sang et al, ; Wang et al, ). Limited reduction of beta sheet content has been achieved for water insoluble RSF scaffolds through water annealing post‐treatment, and glycerol as additive in lyophilization (Chlapanidas et al, ; Chlapanidas et al, ; Lin et al, ; Q. Lu et al, ; Oliveira et al, ; Pei et al, ; Perteghella et al, ).…”