A Nontoxic and Biocompatible\nMethod for Augmenting\nMechanical Strength of Acellular Matrix by Silk Fibroin Impregnation

Biological scaffolds are plagued by poor biomechanical\nproperties\nand untimely degradation. These limitations have yet to be addressed\nwithout compromising their biocompatibility. It is desirable to avoid\ninflammation and have degradation with concomitant host collagen deposition\nor even site-appropriate <i>in situ</i> regeneration for\nthe successful outcome of an implanted biological scaffold. This work\naims to achieve this by utilizing a biocompatible method to modify\nacellular scaffolds by impregnating alkaline-catalyzed citric acid\n(CA) cross-linking between the extracellular matrix proteins and silk\nfibroin (SF)/SF-gelatin (SFG) blends. Combinatorial detergent decellularization\nwas employed to prepare a decellularized porcine liver scaffold (DPL).\nAfter proving the decellularization efficiency, the scaffold underwent\nmodification by vacuum impregnation with CA containing SF (SF100DPL)\nand SFG blends (SFG5050DPL and SFG3070DPL) following pre-cross-linking,\ndrying, and post-cross-linking. The subsequent strength augmentation\nwas demonstrated by significant improvement in tensile strength from\n2.4 ± 0.4 MPa (DPL) to, 3.8 ± 0.7 MPa (SF100DPL), 3.4 ±\n0.7 MPa (SFG5050DPL), and 3.5 ± 0.2 MPa (SFG3070DPL); Young’s\nmodulus from 8.7 ± 1.8 MPa (DPL) to 20 ± 1.9 MPa (SF100DPL),\n13.3 ± 2.6 MPa (SFG5050DPL), and 16 ± 1.2 MPa (SFG3070DPL);\nand suture retention strength from 0.9 ± 0.08 MPa (DPL) to 2.3\n± 0.2 MPa (SF100DPL), 2.8 ± 1.2 MPa (SFG5050DPL), and 2.6\n± 0.9 MPa (SFG3070DPL). The degradation resistance of the modified\nscaffolds was also markedly improved. Being cytocompatible, its ability\nto incite tolerable inflammatory and immune responses was confirmed\nby rat subcutaneous implantation for 14, 30, and 90 days, in terms\nof inflammatory cell infiltration, neoangiogenesis, and <i>in\nvitro</i> cytokine release to assess B-cell and T-cell activation.\nSuch ECM composite scaffolds with appropriate strength and biocompatibility\noffer great promise in soft tissue repair applications such as skin\ngrafting.