Magnesium Hydroxide as a Versatile Nanofiller for 3D-Printed PLA Bone Scaffolds

Polylactic acid (PLA) has attracted much attention in bone tissue engineering due to its good biocompatibility and processability, but it still faces problems such as a slow degradation rate, acidic degradation product, weak biomineralization ability, and poor cell response, which limits its wider application in developing bone scaffolds. In this study, Mg(OH)₂ nanoparticles were employed as a versatile nanofiller for developing PLA/Mg(OH)₂ composite bone scaffolds using fused deposition modeling (FDM) 3D printing technology, and its mechanical, degradation, and biological properties were evaluated. The mechanical tests revealed that a 5 wt% addition of Mg(OH)₂ improved the tensile and compressive strengths of the PLA scaffold by 20.50% and 63.97%, respectively. The soaking experiment in phosphate buffered solution (PBS) revealed that the alkaline degradation products of Mg(OH)₂ neutralized the acidic degradation products of PLA, thus accelerating the degradation of PLA. The weight loss rate of the PLA/20Mg(OH)₂ scaffold (15.40%) was significantly higher than that of PLA (0.15%) on day 28. Meanwhile, the composite scaffolds showed long-term Mg²⁺ release for more than 28 days. The simulated body fluid (SBF) immersion experiment indicated that Mg(OH)₂ promoted the deposition of apatite and improved the biomineralization of PLA scaffolds. The cell culture of bone marrow mesenchymal stem cells (BMSCs) indicated that adding 5 wt% Mg(OH)₂ effectively improved cell responses, including adhesion, proliferation, and osteogenic differentiation, due to the release of Mg²⁺. This study suggests that Mg(OH)₂ can simultaneously address various issues related to polymer scaffolds, including degradation, mechanical properties, and cell interaction, having promising applications in tissue engineering.