Constructing an Anisotropic Triple-Pass Tubular Framework within a Lyophilized Porous Gelatin Scaffold Using Dexamethasone-Loaded Functionalized Whatman Paper To Reinforce Its Mechanical Strength and Promote Osteogenesis.

In bone tissue engineering (BTE), most of the currently developed scaffolds still lack the ability to demonstrate high porosity and high mechanical strength simultaneously or the ability to maintain bioactivity and sustained release of loaded biofactors. In this work, we constructed an anisotropic triple-pass tubular framework within a lyophilized porous GEL scaffold using FP, which was prepared by coating DEX-covered Whatman paper (WP) using the silk fibroin (SF) membrane with β-sheet conformation. This novel structural design endowed the functionalized paper frame (FPF)/scaffold implant high porosity, high mechanical strength, and sustained DEX delivery capability. Specifically, its porosity was as high as 88.2%, approximating that of human cancellous bone. The pore diameters of the implant ranged from 50 to 350 μm with an average pore diameter of 127.7 μm, indicating proper pore sizes for successful diffusion of essential nutrients/oxygen and bone tissue-ingrowth. Owing to the construction of double-network-like structure, the FPF/scaffold implant demonstrated excellent mechanical properties both in dry (174.7 MPa in elastic modulus and 14.9 MPa in compressive modulus) and wet states (59.0 MPa in elastic modulus and 3.3 MPa in compressive modulus), indicating its feasibility for in vivo implantation. Besides, the FPF/scaffold implant exhibited long-term DEX releasing behavior (over 50 days) with constant release rate in phosphate buffered saline (PBS). Murine osteoblasts MC3T3-E1 cultured in the porous FPF/scaffold implant had excellent viability. Furthermore, the cells cocultured with the FPF/scaffold implant showed positive proliferation, osteogenic differentiation, and calcium deposition. Twenty-eight days after implantation, extensive osteogenesis was observed in the rats treated with the FPF/scaffold implants. The anisotropic triple-pass tubular framework of the FPF/scaffold implant demonstrates structural similarities to the long bone. Therefore, this novel FPF/scaffold implant could be a better alternative for long bone defect repair.