Engineering 3D Printed Scaffolds with Tunable Hydroxyapatite

Bone defects from trauma, disease, or surgery demand grafts that mimic native bone in structure and function. Current grafts often lack tunable properties or biological compatibility. While calcium phosphate-based materials are widely used, their mechanical and osteoconductive properties depend heavily on composition and processing. Researchers have explored 3D printing to create customized scaffolds, but precise control over mineral composition remains a challenge. The need for scaffolds that adapt to specific anatomical and functional requirements is well recognized. Limited work has focused on using hydroxyapatite (HA) in fine-tuned compositions for 3D-printed grafts. This gap motivated the development of a CPC bioink system. The study aimed to address the lack of control over HA formation during 3D printing. By adjusting the chemical environment, the team sought to influence scaffold properties like mechanical strength and porosity.

The objective was to engineer 3D-printed bone scaffolds with tunable hydroxyapatite content. The team aimed to develop a method that allows precise control over HA formation during printing. They focused on using a calcium phosphate cement (CPC) bioink with a specific composition of TTCP, DCPA, and PVB in ethanol. The goal was to optimize the scaffold's mechanical and biological properties for bone graft applications. The study sought to investigate how varying the concentration of Na2HPO4 in the printing bath affects HA formation. The team also aimed to assess how these changes influence scaffold porosity and osteoclast activity. Their approach was designed to enable the fabrication of grafts with pre-defined properties. The study aimed to demonstrate the feasibility of this method in creating customized bone scaffolds.

The team used a CPC bioink composed of TTCP, DCPA, and PVB dissolved in ethanol. The ink was extruded through a 210 µm syringe nozzle at room temperature. Three concentrations of Na2HPO4 solution (0.01, 0.1, and 0.5 mol/L) were tested as hardening accelerators. The scaffolds were printed into these baths to induce HA formation. Raman spectroscopy was used to monitor HA formation in real time. X-ray diffraction (XRD) confirmed the crystalline structure of HA in the printed scaffolds. Scanning electron microscopy (SEM) provided visual confirmation of structural changes. The study evaluated how HA content affected mechanical strength, porosity, and osteoclast activity.

Raman spectroscopy confirmed HA formation in all three Na2HPO4 concentrations. XRD analysis showed distinct HA peaks, indicating successful mineralization. SEM images revealed structural differences based on the solution concentration. The 0.5 mol/L bath produced the highest HA content and strongest scaffolds. Scaffolds printed in 0.01 mol/L solution had lower HA content but higher porosity. These variations influenced mechanical properties and osteoclast activity. The study found that scaffold hardness increased with higher HA content. Porosity decreased as HA concentration increased, affecting cell interaction potential.

The study demonstrated that HA formation can be controlled by adjusting the concentration of Na2HPO4 in the printing bath. This method allows for the fabrication of 3D-printed scaffolds with tunable mechanical and biological properties. The team found that higher HA content correlates with increased scaffold hardness. The approach enables the creation of grafts with pre-defined characteristics for specific applications. The findings suggest that this method may improve graft-host integration in bone repair. The study supports the use of CPC bioinks in combination with controlled mineralization baths. The results indicate that this technique may be applied to various anatomical locations. The authors propose that this method could advance personalized bone graft fabrication.