Smart Trap-Capture-Kill Antibacterial System for Infected Microenvironment Improvement and Vascularized Bone Regeneration via Magnetic Thermotherapy

Infected bone defect has gradually become a disastrous complication in orthopedic surgery because of the bacterial biofilm formation both on the surface of the implants and surrounding tissues, which will cause antibiotic resistance and weak postoperative osseointegration. Herein, drug-loaded hollow mesoporous ferrite nanoparticles coated by gelatin (GM/HMFNs) with pomegranate structure are prepared and compounded into calcium magnesium phosphate cement (MCPC) as a Trap-Capture-Kill system to kill bacteria and inhibit biofilm formation efficiently. Under the action of alternating magnetic field (AMF), MCPC/GM/HMFNs/Drug composites exhibit acute magnetic hyperthermal capacity and recruit the free bacteria. Then, the permeability of bacterial cell membrane is increased via reactive oxygen species (ROS) damage of nano-MgO and HMFNs, providing channels through which vancomycin (Van) and ciprofloxacin (CPFX) encapsulated in GM/HMFNs can penetrate. Subsequently, the bacteria are efficiently killed under the synergetic cooperation of magnetothermal effect, ROS damage, and adsorption damage of nano-MgO, and the bioactive ions and drugs. The antibacterial system also presents outstanding pro-osteogenesis and pro-angiogenic capacity in vitro. And it promotes the vascularized bone regeneration of infective femoral defect in SD rats in vivo, providing promising potential for the treatment of infected bone defects through magnetothermal therapy.