Copper-Loaded Microporous\nChitosan Generated within\na 3D-Printed Polylactic Acid-Pearl Scaffold: Structure and Performance

This study employed a combination of fused deposition\nmodeling\n(FDM) 3D printing and freeze-drying techniques to fabricate a polylactic\nacid-pearl-chitosan-copper (PLA-P-CS/Cu) scaffold with a dual-scale\nporous structure and enhanced antibacterial, biological, and mechanical\nperformance. The process began with FDM 3D printing to create a PLA-P\nscaffold featuring an interconnected macroporous structure with a\npore size of hundreds of micrometers. Subsequently, freeze-drying\nwas used to generate CS/Cu microporous foam with a pore size of tens\nof micrometers within the macroporous structure of the PLA-P scaffold.\nThe formation of the dual-scale interconnected porous structure was\nconfirmed through digital microscopy and scanning electron microscopy.\nAdditionally, infrared spectroscopy and X-ray diffraction demonstrated\nthe formation of coordination bonds between the amino and hydroxyl\ngroups of chitosan and Cu<sup>2+</sup> through chelation. Biomineralization\ntest in simulated body fluid indicated that the PLA-P-CS/Cu dual-scale\nporous scaffold enhanced the nucleation, growth, and deposition of\napatite by providing a larger specific surface area and sustained\nrelease of Cu<sup>2+</sup>. The dual-scale porous structure and Cu<sup>2+</sup> release also promoted cell proliferation and osteogenic\ndifferentiation of bone marrow mesenchymal stem cells. Antibacterial\nassay using the plate count method revealed that the Cu-loaded scaffold\nexhibited a 66.72–82.84% antibacterial rate against Escherichia coli, depending on the Cu loading amount.\nFinally, a mechanical test indicated that the compressive strength\nand modulus of the dual-scale porous scaffold were as high as 17.23\nand 295.10 MPa, respectively. This study provides a strategy for developing\ngradient porous bone scaffolds with enhanced antibacterial, biological,\nand mechanical properties through comprehensive optimization of the\nmaterial design, porous structure, and manufacturing processes.