Ultrasound imaging and on-demand therapy of peripheral arterial diseases using H₂O₂-Activated bubble generating anti-inflammatory polymer particles

Muscles of peripheral artery disease (PAD) patients are under oxidative stress associated with a significantly elevated level of reactive oxygen species (ROS) including hydrogen peroxide (H₂O₂). Curcumin is a major active constituent of turmeric and is well known for its highly potent antioxidant, anti-inflammatory and angiogenic effects. We previously reported antioxidant vanillyl alcohol-incorporated copolyoxalate (PVAX) which is designed to rapidly scavenge H₂O₂ and release bioactive vanillyl alcohol and CO₂ in a H₂O₂-triggered manner. In this work, we developed curcumin-loaded PVAX (CUR-PVAX) nanoparticles as contrast-enhanced ultrasound imaging agents as well as on-demand therapeutic agents for ischemic injuries based on the hypothesis that PVAX nanoparticles generate echogenic CO₂ bubbles through H₂O₂-triggered oxidation of peroxalate esters and the merger of curcumin and PVAX exerts H₂O₂-activatable synergistic therapeutic actions. CUR-PVAX nanoparticles also displayed the drastic ultrasound signal in ischemic areas by generating CO₂ bubbles. CUR-PVAX nanoparticles exhibited significantly higher antioxidant and anti-inflammatory activities than empty PVAX nanoparticles and equivalent curcumin in vascular endothelial cells. A mouse model of ischemic injury was used to evaluate the potential of CUR-PVAX nanoparticles as ultrasound imaging agents and on-demand therapeutic agents. CUR-PVAX nanoparticles significantly suppressed the expression of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β). Moreover, CUR-PVAX nanoparticles significantly enhanced the level of vascular endothelial growth factor (VEGF) and platelet endothelial cell adhesion molecule-1 (PECAM-1, also known as CD31), leading to blood perfusion into ischemic tissues. We, therefore, believe that CUR-PVAX nanoparticles hold great translational potential as novel theranostic agents for ischemic diseases such as PAD.