ROS-responsive carrier-free nanodrugs for three-pronged acute ischemic stroke therapy

Acute ischemic stroke (AIS) remains a devastating neurological disorder with limited therapeutic options, in which ischemia/reperfusion-induced oxidative stress, hypoxia, impaired cerebral perfusion, and neuronal injury jointly contribute to disease progression. Here, we report a reactive oxygen species (ROS)-responsive carrier-free nanodrug constructed through microwave-assisted coordination assembly of ruthenium (Ru), L-arginine (L-Arg), and curcumin (Cur), termed RAC. Unlike a simple physical mixture of the three components, RAC represents a coordination-driven carrier-free nanoassembly that integrates multiple therapeutic functions within a single platform, including Ru-associated H₂O₂-responsive oxygen generation, L-Arg-associated nitrite/NO-related signaling, and Cur-mediated antioxidant neuroprotection. RAC formed a distinct supramolecular nanostructure and remained relatively stable under physiological conditions, while undergoing ROS/acidosis-responsive disassembly and Cur release in ischemia/reperfusion-relevant microenvironments. In vitro, RAC exhibited broad ROS-scavenging capability, improved Cur-associated cellular delivery, reduced intracellular ROS and superoxide accumulation, preserved mitochondrial membrane potential, restored redox homeostasis, and attenuated apoptosis in N2a neuronal cells under OGD/R conditions more effectively than the corresponding physical mixture. In vivo fluorescence imaging showed enhanced brain accumulation of RAC after systemic administration. In a tMCAO/R mouse model, RAC promoted cerebral blood flow recovery, reduced infarct volume, preserved cortical neuronal integrity, and improved neurological outcomes compared with both the model and Mix groups. These findings demonstrate that the coordination-driven nanoassembly of RAC contributes to assembly-dependent therapeutic amplification beyond a simple combination of its individual components. This study provides a promising strategy for AIS therapy through the rational design of ROS-responsive, carrier-free nanodrugs integrating free radical scavenging, oxygen generation, NO-related perfusion support, and neuroprotection.