From passive fillers to active implants: A 3D-printed trilayer piezoelectric scaffold recapitulating native bone hierarchy

Critical-sized alveolar bone defects affect over 10 million patients annually, yet current synthetic bone substitutes act as passive osteoconductive fillers with unpredictable outcomes. Native bone, by contrast, achieves robust regeneration through a trilayered hierarchy of cancellous, cortical, and metabolically active periosteal tissues, with intrinsic piezoelectricity converting mechanical loading into endogenous electrical cues. While piezoelectric biomaterials have emerged as promising active implants, existing homogeneous scaffolds fail to recapitulate native bone's structural complexity and electromechanical coupling; to date, no work has combined this trilayer architecture with piezoelectric functionality in a single construct. Here we report a trilayer bioinspired piezoelectric scaffold fabricated via a two-step conformal 3D printing strategy, composed of a strontium-doped β-tricalcium phosphate (Sr-β-TCP) triply periodic minimal surface (TPMS) cancellous layer, a dense cortical layer, and a barium titanate/silk fibroin (BTO/SF) piezoelectric periosteal layer. Under non-invasive low-intensity pulsed ultrasound (LIPUS) stimulation, the scaffold generates bioelectrical signals that support robust osteogenic activity and pro-angiogenic potential in vitro . Transcriptomic profiling reveals that these electrical cues are associated with intracellular calcium influx and upregulation of phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) and Wnt/β-catenin pathways, consistent with enhanced osteogenic differentiation. In a critical-sized bone defect model, the trilayer scaffold with LIPUS achieves substantially superior bone regeneration relative to controls. This work pioneers the integration of native bone hierarchy with piezoelectric functionality into a single active construct, shifting bone tissue engineering from passive filling to bioelectric-guided repair. Coupling structural biomimicry with electroactive stimulation, this strategy holds potential for future bone regenerative applications, including alveolar bone reconstruction.