Porosity-Tunable Zn-0.5Mg Triply Periodic Minimal Surface Scaffolds Enable Immune-Osteogenic Coupling for Customized Bone Regeneration

Abstract

Bone defects remain a clinical challenge due to the limited regenerative capacity of native bone and the lack of biodegradable implants capable of actively regulating the healing microenvironment. Current metallic scaffolds often suffer from an intrinsic trade-off among mechanical properties, degradation behavior, and bioactivity, limiting their therapeutic efficacy in load-bearing bone regeneration. Herein, porosity-tunable Zn-0.5Mg scaffolds with a triply periodic minimal surface (TPMS) structure are fabricated via selective laser melting. By systematically varying scaffold porosities (40, 60, and 80%), the coordinated regulation of mechanical properties, degradation performance, and ion release is achieved. The incorporation of Mg into Zn-0.5Mg enhances mechanical strength and stabilizes degradation behavior, while increasing the porosity accelerates Zn and Mg ion release in a controllable manner. Importantly, the co-released ions promote macrophage polarization, thereby establishing an immunoregulatory microenvironment favorable for bone regeneration. In a rabbit femoral condyle defect model, the implantation of Zn-0.5Mg scaffolds with high porosity (80%) enhanced bone ingrowth into interconnected pore networks and accelerated new bone formation over 14 weeks, without inducing systemic toxicity. Overall, this study establishes a porosity-tunable and immune-osteogenic coupling strategy in biodegradable Zn-0.5Mg scaffolds, offering a generalizable design for customizable and bioactive bone implants.