Dual Nano-Reinforced 3D-Printed Polylactic Acid Scaffolds for Antibacterial and Osteogenic Applications

To address the challenge of infectious bone defects, bone scaffolds must not only satisfy requirements for porous structure, mechanical properties, and biological performance but also possess antibacterial functionality. In this study, we proposed dual doping of Mg(OH)₂ and CuO nanoparticles into polylactic acid (PLA) and used the material extrusion (MEX) 3D printing technology to fabricate a PLA/Mg(OH)₂/CuO nanocomposite porous bone scaffold. The experimental results show that due to the dispersion strengthening effect of inorganic nanoparticles, the mechanical properties of the scaffolds are significantly enhanced. The compressive strength of the PLA/5Mg(OH)₂/1CuO scaffold reaches 21.18 MPa, representing a 67.17% increase compared to pure PLA. Degradation experiments reveal that Mg(OH)₂ and CuO nanoparticles create pitting corrosion in the matrix and accelerate the degradation of the matrix. By the 28th day, the weight loss of the PLA/5Mg(OH)₂/5CuO scaffold was as high as 6.22%. By using a PLA matrix to encapsulate the nanoparticles, the nanocomposite scaffolds can continuously release magnesium and copper ions for more than 28 days without an obvious burst release phenomenon. The ions mediated by the released magnesium and copper enhance the biomineralization ability of the scaffold in SBF. Immunofluorescence and ALP staining indicate that the incorporation of Mg(OH)₂ nanoparticles and an appropriate amount of CuO nanoparticles is beneficial for cell growth and differentiation. Antibacterial experiments using the plate count method reveal that the material doped with two kinds of nanoparticles has achieved remarkable results in eliminating Escherichia coli and Staphylococcus aureus, and its effect is closely related to the CuO content. SEM indicated that the bacteria were subjected to strong antibacterial effects from the nanoparticles, leading to visible deformation, rupture, and leakage of intracellular substances. This study demonstrates that the dual doping of metal oxides and hydroxides can enhance multiple properties of polymer bone scaffolds, rendering them more suitable for applications in bone tissue engineering.