Meso-reconstructed silk fibroin/iron oxide nanoparticle composites dominated by silk I structures through unidirectional nanopore dehydration for potential application in bone regeneration

Silk fibroin (SF), an innovative bioactive material widely used in tissue engineering, is commonly employed to construct biological scaffolds. Conventional approaches for fabricating water-insoluble SF-based films, such as evaporative dehydration and induced annealing with organic solvents, often result in membranes dominated by silk II structures with poor ductility and intricate preparation processes. In this study, inspired by the self-assembly behavior observed in SF solution during dialysis, we developed a unidirectional nanopore dehydration (UND) method to prepare SF-based membranes (SFM_U) dominated by silk I structures. The SF solution underwent direct dehydration through UND, yielding enhanced water stability. Furthermore, to enhance the overall properties of SFM_U and apply it to the field of bone tissue engineering, biocompatible iron oxide nanoparticles (IONPs) were incorporated into SFM_U, leading to the creation of three types of SFM_U-IONPs by varying the added IONP amounts. The results demonstrated that SFM_U-IONPs formed water-insoluble silk I structures with a lower elastic modulus, and the addition of IONPs endowed neat SFM_U with improved structural order, porosity, and mechanical properties. Additionally, SFM_U-IONPs demonstrated exceptional biocompatibility towards pre-osteoblast cell line MC3T3-E1 as evidenced by their non-toxic effects on cell viability and attachment. Taken together, SFM_U-IONPs with enhanced properties could serve as promising repair composite membranes for bone regeneration in clinical applications.