Copper-Loaded Microporous Chitosan Generated within a 3D-Printed Polylactic Acid-Pearl Scaffold: Structure and Performance

Abstract

This study employed a combination of fused deposition modeling (FDM) 3D printing and freeze-drying techniques to fabricate a polylactic acid-pearl-chitosan-copper (PLA-P-CS/Cu) scaffold with a dual-scale porous structure and enhanced antibacterial, biological, and mechanical performance. The process began with FDM 3D printing to create a PLA-P scaffold featuring an interconnected macroporous structure with a pore size of hundreds of micrometers. Subsequently, freeze-drying was used to generate CS/Cu microporous foam with a pore size of tens of micrometers within the macroporous structure of the PLA-P scaffold. The formation of the dual-scale interconnected porous structure was confirmed through digital microscopy and scanning electron microscopy. Additionally, infrared spectroscopy and X-ray diffraction demonstrated the formation of coordination bonds between the amino and hydroxyl groups of chitosan and Cu²⁺ through chelation. Biomineralization test in simulated body fluid indicated that the PLA-P-CS/Cu dual-scale porous scaffold enhanced the nucleation, growth, and deposition of apatite by providing a larger specific surface area and sustained release of Cu²⁺. The dual-scale porous structure and Cu²⁺ release also promoted cell proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells. Antibacterial assay using the plate count method revealed that the Cu-loaded scaffold exhibited a 66.72–82.84% antibacterial rate against Escherichia coli, depending on the Cu loading amount. Finally, a mechanical test indicated that the compressive strength and modulus of the dual-scale porous scaffold were as high as 17.23 and 295.10 MPa, respectively. This study provides a strategy for developing gradient porous bone scaffolds with enhanced antibacterial, biological, and mechanical properties through comprehensive optimization of the material design, porous structure, and manufacturing processes.