Abstract
The repair of large bone defects remains challenging and often requires graft material due to limited availability of autologous bone. In clinical settings, collagen sponges loaded with excessive amounts of bone morphogenetic protein 2 (rhBMP-2) are occasionally used for the treatment of bone non-unions, increasing the risk of adverse events. Therefore, strategies to reduce rhBMP-2 dosage are desirable. Silk scaffolds show great promise due to their favorable biocompatibility and their utility for various biofabrication methods. For this study, we generated silk scaffolds with axially aligned pores, which were subsequently treated with 10× simulated body fluid (SBF) to generate an apatitic calcium phosphate coating. Using a rat femoral critical sized defect model (CSD) we evaluated if the resulting scaffold allows the reduction of BMP-2 dosage to promote efficient bone repair by providing appropriate guidance cues. Highly porous, anisotropic silk scaffolds were produced, demonstrating good cytocompatibility in vitro and treatment with 10× SBF resulted in efficient surface coating. In vivo, the coated silk scaffolds loaded with a low dose of rhBMP-2 demonstrated significantly improved bone regeneration when compared to the unmineralized scaffold. Overall, our findings show that this simple and cost-efficient technique yields scaffolds that enhance rhBMP-2 mediated bone healing.
Highlights
IntroductionWhile adult bone generally heals without complication, resulting in full recovery of bone tissue and function, approximately 10% of all fractures do not heal adequately and appropriate stability is not achieved
Licensee MDPI, Basel, Switzerland.While adult bone generally heals without complication, resulting in full recovery of bone tissue and function, approximately 10% of all fractures do not heal adequately and appropriate stability is not achieved
Pore interconnectivity was achieved by placing an array with polypropylene rods within the freezing silk fibroin solution and subsequent removal of the array after freeze-drying (Figure 1B, bottom)
Summary
While adult bone generally heals without complication, resulting in full recovery of bone tissue and function, approximately 10% of all fractures do not heal adequately and appropriate stability is not achieved. Supply is often limited, and these treatment options have demonstrated varied success rates. They can be associated with donor site morbidity such as persisting pain or, in rare cases, fractures of the pelvis [6]. The use of allografts or synthetic biomaterials [7,8] have been developed to overcome these limitations. These substitute materials often lack osteogenic properties [9]
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