Fabrication of β-TCP ceramic scaffold with hierarchical pore structure using 3D printing and porogen: Investigation of osteoinductive and bone defects repair properties

Abstract

This study aimed to enhance the bone-forming performance of β-TCP ceramic scaffolds by incorporating porosity-generating polystyrene microspheres. The microspheres were blended with the β-TCP powder and sintered to produce porous ceramics with varying porosities and mesopore sizes. Optimal conditions for manufacturing scaffolds with hierarchical pore structures were identified, and their impact on ectopic bone formation and bone defect repair was assessed. Increasing the volume of microspheres enhanced porosity while reducing compressive strength. The optimal microsphere content was determined to be 20 %, which resulted in increased alkaline phosphatase (ALP) activity and up-regulated expression of osteogenesis-related genes. Introduction of microspheres of different sizes (10, 20, 40, and 70 μm) effectively yielded porous β-TCP ceramics with mesopores that promoted cell attachment and spreading. Scaffolds with 40 μm mesopores demonstrated superior cell attachment and enhanced osteogenic differentiation. The integration of microspheres and 3D printing enabled the fabrication of hierarchical porous β-TCP ceramic scaffolds, featuring mm-scale macropores between struts, mesopores ranging from 10 to 100 μm within the struts, and micropores smaller than 10 μm. Stem cells cultured on scaffolds with 500 μm macropores exhibited elevated osteogenic gene expression compared to those with 300 μm macropores. Both 40 μm mesopores and 500 μm macropores accelerated degradation of the scaffolds, with the macropores exerting a more pronounced effect. New bone tissue can grow into the mesopores within the struts of the scaffold. Moreover, the β-TCP ceramic scaffold with 40 μm mesopores and 500 μm macropores demonstrated superior ectopic osteogenic performance and bone defect repair efficacy. These findings hold significance in addressing the challenges linked to the absence of mesopores and suboptimal osteogenic effects in conventional β-TCP ceramics. It is anticipated that these outcomes will contribute to the expanded utilization of β-TCP ceramic scaffolds in clinical bone repair applications.