Research on the performance of HAP/ALG composite bone scaffolds with bone unit structure

Area of Science:

• Biomaterials Science
• Tissue Engineering
• Biomedical Engineering

Background:

• Replicating bone's mechanical anisotropy and promoting angiogenesis are key challenges in bone tissue engineering.
• Current 3D printing methods often require multi-step processes or material modifications.

Purpose of the Study:

• To develop a single-step 3D printing strategy for fabricating bone tissue engineering scaffolds with tunable mechanical anisotropy and pro-angiogenic properties.
• To create hollow fiber scaffolds mimicking the Haversian canal unit.

Main Methods:

• A path-programmable coaxial reactive flow strategy using radial 3D printing with a hydroxyapatite/sodium alginate (HAP/ALG) composite.
• Modulation of HAP/ALG mass ratio and fiber arrangement path to control mechanical anisotropy.
• In vitro and in vivo experiments using adipose-derived stem cells (ADSCs) and structural/mechanical characterization (Micro-CT, SEM, mechanical testing).

Main Results:

• Scaffolds with a HAP/ALG ratio of 2:1 and longitudinal fiber arrangement exhibited an axial to radial compressive modulus ratio of approximately 2.23, approaching natural cortical bone.
• Hollow fiber scaffolds showed enhanced formation of early vascular-like structures compared to solid fibers in vivo.
• The method allows synchronous construction of hollow structures and modulation of mechanical anisotropy in a single step.

Conclusions:

• The proposed 3D printing strategy simplifies fabrication and enhances control over scaffold architecture and mechanical properties.
• The developed scaffolds possess bone-mimicking mechanical anisotropy and pro-angiogenic capabilities.
• Further optimization of the degradation rate of calcium alginate is necessary for better integration with tissue growth.