Piezoelectric 3D-Printed Scaffolds Coupled with Ultrasound Stimulation for Improved Bone Tissue Engineering Strategies

The increasing incidence of trauma- and osteoporosis-related non-union fractures in the aging population has intensified the clinical demand for bone substitutes, prompting growing interest in bone tissue engineering (BTE) strategies. A promising BTE approach is the development of biomimetic scaffolds capable of providing structural support while promoting bone tissue regeneration. Bone homeostasis and repair rely considerably on the piezoelectric properties of bone tissue, derived mainly from its type I collagen fibers and hydroxyapatite-rich extracellular matrix[1]. Additionally, additive manufacturing technologies (Fused Deposition Modelling (FDM)) have been widely adopted in BTE, as they enable the reproducible and scalable fabrication of scaffolds with precise control over their structural architecture, microporosity, and mechanical properties. Thus, combining piezoelectric scaffolds with ultrasound (US) wireless mechanical stimulation offers a novel strategy to deliver targeted electrical stimuli to enhance bone regeneration. In this work, 3D-printed porous cylindrical scaffolds made from different piezoelectric filaments—poly-l-lactic acid (PLLA), polyvinylidene fluoride (PVDF), and conductive PVDF—were developed to compare their physicochemical properties and osteogenic performance. SEM and micro-CT analysis showed that all scaffolds presented homogeneous morphology and a high printing fidelity with low defects and pore sizes matching the CAD model. All constructs except PLLA were hydrophobic, and PLLA exhibited mechanical properties closest to native trabecular bone. Conductive PVDF scaffolds had a significantly higher piezoelectric charge coefficient. Notably, a previously optimized US stimulation protocol [2] (intensity=250 mW/cm²; freq=3MHz; duty cycle–20%; duration per scaffold–3 mins (every 2 days) for 3 weeks) promoted the osteogenic differentiation of human bone-marrow mesenchymal stem/stromal cells(hBMSCs), especially for PLLA scaffolds, as evidenced by increased ALP activity and up-regulated osteogenic markers (Runx2/COL1A1). Overall, our results highlight a clear synergy between the 3D scaffolds’ piezoelectric features and US stimulation on the enhancement of the osteogenic differentiation of hBMSCs, highlighting this strategy potential for improved BTE clinical applications.