Osteogenic Potential of 3D-Printed Porous Poly(lactide-<i>co</i>-trimethylene carbonate) Scaffolds Coated with Mg-Doped Hydroxyapatite

Extrusion-based 3D printing of thermoplastic polymers presents significant potential for bone tissue engineering. However, a key limitation is the frequent absence of filament porosity and the inherent osteoconductive properties. This study addresses these challenges by fabricating poly(lactide-<i>co</i>-trimethylene carbonate) (PLATMC) scaffolds with dual-scale porosity: macroporosity achieved through controlled filament spacing and microporosity introduced via NaCl leaching. The inclusion of NaCl generated rough, porous surfaces that were well-suited for dip-coating with magnesium-carbonate-doped hydroxyapatite (MgCHA), thereby imparting osteoconductive functionality. Thermal analysis revealed that salt incorporation had minimal impact on the polymer's thermal stability. Rheological studies and computational modeling indicated that NaCl reduced the viscosity under shear, leading to enhanced printability and faster extrusion speeds. After leaching, the scaffolds exhibited approximately 34% microporosity, which significantly increased water uptake and swelling capacity, despite the roughened surfaces slightly elevating hydrophobicity. The mechanical properties of PLATMC (with nonporous filaments) and p-PLATMC (with porous filaments) scaffolds showed a modulus of elasticity of 566 ± 118 and 101 ± 20 MPa, respectively, with strain values of 178 ± 54% and 84 ± 28%. Biological evaluations highlighted the compatibility of the p-PLATMC scaffolds. Cell viability and proliferation assays confirmed sustained cellular interaction over a 14 day period. Notably, alkaline phosphatase (ALP) activity was elevated in the porous scaffolds, and the MgCHA coating significantly enhanced mineral deposition by day 28, suggesting improved osteogenic potential. In conclusion, this study presents a robust strategy for fabricating 3D-printed PLATMC scaffolds with integrated filament porosity, offering a viable platform for osteoconductive coatings in bone tissue engineering applications.