Macro-micro analysis of the physical and biological properties of 3D-printed hydroxyapatite/β-tricalcium phosphate scaffolds with varying polyvinyl alcohol concentrations

Abstract

The concentration of the binder is a key factor affecting the quality of 3D-printed bone scaffolds. In this study, a macro–micro analysis was conducted to evaluate the effects of varying concentrations of polyvinyl alcohol (PVA) aqueous solution on the physical and biological properties of hydroxyapatite/β-tricalcium phosphate bone scaffolds. Both molecular dynamics (MD) simulations and experimental approaches were employed. The MD simulations analyzed microscopic interactions between PVA and ceramic powders by assessing changes in chain length at different concentrations. Experimentally, slurries containing 5–15% wt% PVA were characterized in terms of solid content, zeta potential, and extrusion rheology. Bone scaffolds were fabricated via 3D printing followed by freeze-drying, and their porosity, mechanical properties, dimensional shrinkage, and swelling behavior were examined. In vitro tests were conducted to assess biological performance. The results indicated that hydrogen and ionic bonding between PVA and ceramic powders were the primary mechanisms of adhesion. Increased chain length led to higher Cauchy pressure, thereby enhancing the mechanical properties of the material. Higher PVA concentrations produced slurries with increased solid content and shear-thinning capabilities, improving printability. The resulting bone scaffolds exhibited higher mechanical properties and shrinkage during drying but showed reduced porosity and swelling capability. In vitro experiments revealed that increasing PVA concentration decreased both the porosity and ion concentration of the bone scaffolds, thereby reducing their bioactivity. These findings provide a theoretical basis for optimizing binder concentration in 3D-printed bone scaffolds by linking slurry characteristics to scaffold performance.

Keywords

Biological properties / Extrusion rheology / Freeze-drying / Mechanical properties / Molecular dynamics simulation

Funding

This work was supported by the National Natural Science Foundation of China (grant no: 52365053).

Conflict of Interest

The authors declare they have no competing interests.

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