Controlled Cryogelation and Catalytic Cross-Linking Yields Highly Elastic and Robust Silk Fibroin Scaffolds

Abstract

Silk biomaterials with tunable mechanical properties and biological properties are of special importance for tissue engineering. Here, we fabricated silk fibroin (SF, from Bombyx mori silk) scaffolds from cryogelation under controlled temperature and catalytic cross-linking conditions. Structurally, the cryogelled scaffolds demonstrated a greater β-sheet content but significantly smaller β-sheet domains compared to that without chemical cross-linking and catalyst. Mechanically, the cryogelled scaffolds were softer and highly elastic under tension and compression. The 120% tensile elongation and >85% recoverable compressive strain were among the best properties reported for SF scaffolds. Cyclic compression tests proved the robustness of such scaffolds to resist fatigue. The mechanical properties, as well as the degradation rate of the scaffolds, can be fine-tuned by varying the concentrations of the catalyst and the cross-linker. For biological responses, in vitro rat bone mesenchymal stem cell (rBMSC) culture studies demonstrated that cryogelled SF scaffolds supported better cell attachment and proliferation than the routine freeze-thawed scaffolds. The in vivo subcutaneous implantation results showed excellent histocompatibility and tissue ingrowth for the cryogelled SF scaffolds. This straightforward approach of enhanced elasticity of SF scaffolds and fine-tunability in mechanical performances, suggests a promising strategy to develop novel SF biomaterials for soft tissue engineering and regenerative medicine.

Macroporous Silk Nanofiber Cryogels with Tunable Properties

“…EGDE and TEMED as the crosslinker and the catalyst were used to crosslink SF in aqueous solutions, inducing the cryogelation after the freezing–thawing process. , Both amino and hydroxyl groups of SF could be reacted in the system. , However, the continuous conformation changes of SF in aqueous solutions result in the uncontrollable redistribution of active groups, which then influences the outcomes in the SF cryogels. Unlike heterogeneous nanoparticles in traditional SF solution, SSFs have homogeneous nanofibrous structures and rich hydrophilic groups on the surface, resulting in higher HRP crosslinking than that of traditional SF solutions .…”

“…FTIR spectra showed typical amorphous structures (characteristic band at 1642 cm –1 ) , in SSF and SF solutions (Figure b). The SSFs were used to form cryogels under the reported crosslinking process . SFs prepared via the traditional method , were also crosslinked under same conditions as a control.…”

“…Here, amorphous short SSFs were used to fabricate cryogels via the reported crosslinking processes . Under same reaction conditions, the cryogels with better mechanical properties were prepared.…”

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

“…Silk fibroin (SF) biomaterials are promising bone regenerative matrices due to the biocompatibility, excellent and tunable mechanical properties, and ease of materials fabrication [ [9] , [10] , [11] , [12] ]. SF-based scaffolds, films and hydrogels have been developed to repair various bone defects [ 9 , [13] , [14] , [15] ]. The cytocompatibility and bioactivity of these matrices were further improved by changing nano-micro structures, anisotropic topography, degradation behavior and mechanical performance [ [16] , [17] , [18] , [19] ].…”

Preparation of a novel regenerated silk fibroin-based hydrogel for extrusion bioprinting

“…25 As an abundant natural protein, regenerated silk fibroin (RSF) extracted from Bombyx mori silkworm silk has very good processability and can be prepared into a variety of materials with different traits, including membranes, microspheres, fibers, hydrogels, scaffolds, etc. [26][27][28][29][30] Due to their good biocompatibility, excellent processability, and comprehensive mechanical properties, RSF-based materials have also attracted the attention of researchers in the field of 3D bioprinting. For example, a simple method is to directly deposit highconcentration RSF aqueous solution (28-30 wt%) into 86% methanol aqueous solution and the obtained scaffold had good biocompatibility and supported the adhesion and growth of human mesenchymal stem cells (hMSCs).…”