Low-Intensity Pulsed Ultrasound Responsive Scaffold Promotes Intramembranous and Endochondral Ossification via Ultrasonic, Thermal, and Electrical Stimulation.

Multiple physical stimuli are expected to produce a synergistic effect to promote bone tissue regeneration. Low-intensity pulsed ultrasound (LIPUS) has been clinically used in bone repair for the mechanical stimulation that it provides. In addition, LIPUS can also excite the biomaterials to generate other physical stimuli such as thermal or electrical stimuli. In this study, a scaffold based on decellularized adipose tissue (DAT) is established by incorporating polydopamine-modified multilayer black phosphorus nanosheets (pDA-mBP@DAT). Their effect on bone repair under LIPUS stimulation and the potential mechanisms are further investigated. This scaffold possesses piezoelectric properties and generates a mild thermogenic stimulus when stimulated by LIPUS. With superior properties, this scaffold is demonstrated to have good cytocompatibility in vitro and in vivo. Simultaneously, LIPUS promotes cell attachment, migration, and osteogenic differentiation in the pDA-mBP@DAT scaffold. Furthermore, the combined use of pDA-mBP@DAT and LIPUS significantly affects the regenerative effect in rat models of critical-sized calvarial defects. The possible mechanisms include promoting osteogenesis and neovascularization and activating the Piezo1. This study presents insight into speeding up bone regeneration by the synergistic combination of LIPUS and pDA-mBP@DAT scaffolds.