Calcium phosphate based three-dimensional cold plotted bone scaffolds for critical size bone defects

Current bone grafting methods face limitations due to donor site complications and disease transmission risks. Calcium phosphate-based substitutes offer an alternative, but their fabrication often requires high temperatures or complex processes. Recent studies have explored room-temperature fabrication techniques to improve scaffold customization and biological integration. While prior research has demonstrated the potential of calcium phosphate for bone regeneration, the need for a printable, resorbable material remains unmet. This gap motivated the development of a cold-plotted cement composition. The approach aims to address the limitations of existing grafting methods while enabling the incorporation of therapeutic agents. Customization of scaffolds is essential for clinical translation, yet few studies have tested such materials in large animal models. This work builds on prior findings by introducing a novel fabrication process and evaluating its biological and structural performance.

The study aimed to develop a cold-plotted bone cement composition suitable for room-temperature fabrication of customized scaffolds. The specific problem addressed is the lack of printable, resorbable materials that support bone regeneration without requiring high-temperature processing. The motivation stems from the clinical need for alternatives to autografts and allografts. The proposed solution involves a cement formulation containing β-tricalcium phosphate, polyethylene glycol, and trisodium citrate. The objective was to evaluate the material's biocompatibility and bone regeneration capabilities. The study also sought to compare scaffold performance with autografts in a large animal model. A key question was whether the new cement could support cell proliferation and differentiation. The ultimate goal was to establish a scaffold material that could serve as a foundation for future bone substitutes.

The cement composition was prepared using β-tricalcium phosphate, polyethylene glycol, and trisodium citrate. The mixture was extruded using freeform fabrication at room temperature to create three-dimensional scaffolds. In vitro tests assessed cell proliferation and differentiation using ATDC5 cells in scaffold-conditioned media. The scaffolds were implanted in the iliac wing of sheep to evaluate bone remodelling. Mineral volume and density were measured after 12 weeks using microcomputed tomography. Empty defects and autograft-filled defects served as controls. The study included histological analysis to assess tissue integration. The fabrication process was optimized to ensure structural integrity and resorption properties.

The cement composition allowed successful scaffold fabrication at room temperature. In vitro tests showed that ATDC5 cells proliferated and differentiated in scaffold-conditioned medium. Implantation in sheep demonstrated bone remodelling throughout the defects. Scaffolds outperformed empty defects in both mineral volume and density after 12 weeks. Scaffold-treated defects had mineral density comparable to autograft-filled defects. The mineral volume in scaffold-treated defects was at least equal to that in autograft-treated defects. Histological analysis confirmed tissue integration and scaffold resorption. The results suggest that the material supports de novo bone formation in critical size defects.

The formulated cement composition is suitable for room-temperature scaffold production. The material supports cell proliferation and differentiation in vitro. In vivo results indicate effective bone remodelling in critical size defects. Scaffolds outperformed empty defects in mineral volume and density. Scaffold-treated defects matched autograft-filled defects in mineral density. The mineral volume in scaffold-treated defects was comparable to autograft-treated defects. The material's resorption properties and structural integrity support its potential as a bone substitute. The findings suggest that the cement composition can serve as a basis for future bone substitutes.