Targeted Therapy of Ischemic Stroke via Crossing the Blood-Brain Barrier Using Edaravone-Loaded Multiresponsive Microgels.

Ischemic stroke, as a prevalent neurological disorder, often results in rapid increases in the production of reactive oxygen species (ROS) and inflammatory factors in the focal ischemic area. Though edaravone is an approved treatment, its effect is limited due to its weak ability to cross the blood-brain barrier (BBB) and short half-life. Other effective pharmacological treatment options are clearly lacking. In this study, PNIVDBrF-3-Eda (also named MG-3-Eda) was prepared using a thermo- and pH dual-responsive PNIVDBrF microgel. These were designed with a positively charged network, as synthesized by simultaneous quaternization cross-linking and surfactant-free emulsion copolymerization, to be loaded with the negatively charged edaravone. We then investigated whether such a targeted delivery of edaravone could provide enhanced neuroprotection. Cytotoxicity assays confirmed that the microgel (<1 mg/mL) exhibited promising cytocompatibility with no remarkable effect on cell viability, cell cycle regulation, or apoptosis levels. In vitro and in vivo experiments demonstrated that the microgels could successfully penetrate the blood-brain barrier where efficient BBB crossing was observed after disruption of the BBB due to ischemic injury. This enabled MG-3-Eda to target the cerebral ischemic area and achieve local release of edaravone. Treatment with MG-3-Eda significantly reduced the cerebral infarct area in transient middle cerebral artery occlusion (tMCAO) mice and significantly improved behavioral scores. MG-3-Eda treatment also prevented the reduction in NF200 expression, a neuronal marker protein, and attenuated microglia activation (as detected by Iba1) in the local ischemic area via local antioxidant and anti-inflammatory effects. A superior neuroprotective effect was noted for MG-3-Eda compared to that for free edaravone. Our results indicate that MG-3-Eda administration represents a clear potential treatment for cerebral ischemia via its targeted delivery of edaravone to ischemic areas where it provides significant local antioxidant and anti-inflammatory effects.