Ion‐Driven Regulation of Ca ^{2 +} Flow by Ti/Zn Composite Activates ERK/MAPK Signaling and Maintains Mitochondrial Homeostasis to Promote Macrophage‐Mediated Bone Regener

ABSTRACT

The field of tissue engineering is transitioning from bioinert to bioactive materials that actively regulate host biology. Here, we developed a 3D‐printed porous Ti scaffold infiltrated with molten Zn to form an interpenetrating Ti/Zn composite with immunomodulatory and osteogenic bioactivity. Corrosion characterization revealed sustained and stable Zn ²⁺ release. In vivo evaluation using a rat rib implantation model confirmed enhanced peri‐implant bone regeneration, accompanied by localized Ca/P deposition at Zn degradation sites, indicating biofunctionally favorable degradation. In vitro, Ti/Zn extract induced a shift toward an anti‐inflammatory M2 macrophage phenotype. Mechanistically, Zn ²⁺ altered intracellular Ca ²⁺ dynamics, elevating cytoplasmic Ca ²⁺ while preventing mitochondrial Ca ²⁺ overload, thereby preserving mitochondrial membrane potential and inner membrane protein complex stability. This Ca ²⁺ redistribution selectively activated ERK/MAPK signaling, linking ionic cues to mitochondrial homeostasis, reduced ROS generation, and suppression of cytochrome c‐mediated intrinsic apoptosis. The immunoregulatory secretome from Ti/Zn‐reprogrammed macrophages further promoted osteoblast proliferation, ALP activity, and osteogenic gene/protein expression. In vivo immunohistochemistry and immunofluorescence validated a remodeled immune microenvironment with attenuated oxidative stress and active new bone synthesis. Overall, the Ti/Zn composite integrates bone‐mimetic architecture with ion‐driven immunometabolic regulation, highlighting its potential as a next‐generation bioactive bone implant.