Ultrasound-responsive gallium protoporphyrin and oxygen loaded perfluoropentane nanodroplets for effective sonodynamic therapy of implant infections

Implant infections are severe complications in clinical treatment, which often accompany the formation of bacterial biofilms with high antibiotic resistance. Sonodynamic therapy (SDT) is an antibiotic-free method that can generate reactive oxygen species (ROS) to kill bacteria under ultrasound (US) treatment. However, the extracellular polymeric substances (EPS) barrier of bacterial biofilms and the hypoxic microenvironment significantly limit the antibiofilm activity of SDT. In this study, lipid-shelled perfluoropentane (PFP) nanodroplets loaded with gallium protoporphyrin IX (GaPPIX) and oxygen (O₂) (LPGO NDs) were developed for the treatment of implant infections. Under US stimulation, LPGO NDs undergo the cavitation effect and disrupt the biofilm structure like bombs due to liquid-gas phase transition. Meanwhile, the LPGO NDs release O₂ and GaPPIX upon US stimulation. The released O₂ can alleviate the hypoxic microenvironment in the biofilm and enhance the ROS formation by GaPPIX for enhanced bacterial killing. In vivo experimental results demonstrate that the LPGO NDs can efficiently treat implant infections of methicillin-resistant Staphylococcus aureus (MRSA) in a mouse model by disrupting the biofilm structure, alleviating hypoxia, and enhancing bacterial killing by SDT. Therefore, this work provides a new multifunctional sonosensitizer to overcome the limitations of SDT for treating implant infections.