3D printing and performance of biodegradable continuous fiber-reinforced calcium phosphate ceramic scaffolds

Calcium phosphate (CaP) ceramics, with similar consitutent to natural bone minerals, exhibit excellent biological activity, biocompatibility, and bone conduction properties and have been one of the main alternatives to bone grafts. Porous CaP scaffolds can provide a three-dimensional space and biocompatible surface for bone ingrowth. However, the inherent brittleness of ceramics limits their wide application. Continuous PGA fiber-reinforced calcium phosphate ceramic (PGA/HTC) scaffolds were fabricated using a micro-level single filament continuous fiber (30 μm~60 μm) reinforced composite 3D printing device developed in this study. This device controls fiber feeding, rolling combination of fiber and matrix, and fiber covered with matrix through adjusting fiber feeding speed and deformation of elastic component on the surface of feeding roller. It solves the issues of feeding micron-sized fibers and their integration with the slurry during the 3D printing process and can be used to print micron-scale continuous fiber-reinforced composites. Compressive strength of the fabricated PGA/HTC scaffold is 3.84 MPa, which falls within the range of cancellous bone. Maximum strain of the PGA/HTC scaffold is 13.23%, which is 192.7% higher than that of the HTC scaffold (4.52%). This indicates that the introduction of continuous PGA fibers effectively enhances the toughness and deformation capacity of the bioceramic scaffold, while reducing its brittleness. After 7 days of immersion in SBF, the mass loss rate of the scaffold is 32.8%, while there is little mass change after 14 days. This indicates that during the initial immersion period, the dissolution of the scaffold exceeds the rate of apatite formation, and equilibrium is reached thereafter. At the same time, apatite forms on the surface of the matrix and fibers, as well as in the voids between the matrix and fibers. Over time, the thickness of the apatite layer increases. The Ca/P ratio of the apatite layer ranges from 1.45 to 1.69, indicating that the fabricated PGA/HTC scaffold has excellent degradation performance and bioactivity.