Piezoelectric Iridium-Doped Bismuth Ferrite/Sodium Alginate Hydrogel for Antibiosis and Stimulating Osteoblastic Differentiation

The creation of a piezoelectric nanozyme with a piezoelectric effect coupled with nanozyme activity to eradicate bacteria and facilitate osteoblast response is a novel strategy for the repair of infected bone defects. Herein, iridium-doped bismuth ferrite nanoparticles (IBFO) with improved piezoelectricity and multiple enzyme-like activities were prepared via the sol–gel method. Triggered by ultrasound (US), the piezoelectric effect of IBFO boosted the separation of electron/hole pairs and accelerated electron transfer that enhanced sonodynamic efficiency and enzyme-like activities. Moreover, a reactive oxygen species (ROS)-responsive sodium alginate-based piezoelectric hydrogel containing IBFO nanoparticles was prepared (IBFO-SAPS). In simulating a bacterial infection microenvironment (pH = 5.5) triggered by US (power > 0.5 W/cm2), IBFO-SAPS demonstrated remarkable antibacterial efficacy via the combination of piezoelectrically enhanced sonodynamic efficiency and peroxide (POD)-like activity that generated a large amount of ROS for collaborative eradication of bacteria. In simulating a physiological microenvironment (pH 7.4), under US (≤0.5 W/cm2) the piezoelectric effect of IBFO-SAPS improved the catalase (CAT)-like activity for scavenging intracellular ROS and generating oxygen, which provided a favorable microenvironment for cell growth due to the alleviation of oxidative stress and hypoxia. Moreover, the electrical stimulation generated by the piezoelectric effect of IBFO-SAPS boosted osteoblast proliferation and differentiation. The developed hydrogel significantly rooted out bacteria and facilitated osteoblast response through the piezoelectric effect, enhancing sonodynamic efficiency and nanozyme activity. This study provided a new strategy to design anti-infective biomaterials for the treatment of infected bone defects.