Ultrasound-Responsive Thermoplastic Piezoelectric Composites For Jawbone Repair

Jawbone defects pose significant challenges for regeneration. This study developed a polymer-based artificial bone material by integrating polylactic acid (PLA), hydroxyapatite (HA), and potassium sodium niobate (KNN) through stereoisomeric methods. The material exhibits ultrasound-responsive piezoelectric properties and thermoplasticity, aiming to enhance osteogenesis via microelectrical stimulation. The material’s composition, morphology, and thermoplasticity were characterized using X-ray diffraction, energy-dispersive X-ray spectroscopy, scanning electron microscopy and rheological tests. Piezoelectric properties were confirmed via piezoresponse force microscopy. Degradation was evaluated through in vitro assays and subcutaneous implantation in rats. In vitro, biocompatibility and osteogenic potential under ultrasound were assessed using CCK8, western blotting, and immunofluorescence. RNA sequencing explored osteogenic mechanisms. In vivo, the material was tested in rat mandibular defects, with micro-CT, H&E staining, and immunohistochemistry evaluating bone regeneration. The composite material exhibited excellent thermoplasticity and ultrasound-responsive piezoelectricity. In vitro, it showed good biocompatibility and promoted osteogenic differentiation under ultrasound stimulation, with increased expression of RUNX2 and osteopontin. RNA-Seq revealed that ultrasound-induced microcurrents activated the local renin-angiotensin-aldosterone system (Local RAAS), enhancing osteogenesis. Western blotting and immunofluorescence revealed an upregulation of the osteogenesis-related marker AT2R and a downregulation of the osteoclast-related marker AT1R. In vivo, the material significantly promoted the repair of critical mandibular defects by activating AT2R-mediated local RAAS signaling. The ultrasound-responsive piezoelectric composite material generates microcurrents under ultrasound stimulation, activating Local RAAS to enhance osteogenic differentiation and promote effective repair of critical bone defects.