A simple polydopamine‐based platform for engineering extracellular vesicles with brain‐targeting peptide and imaging probes to improve stroke outcome

Extracellular vesicles (EVs) have shown great potential for treating various diseases. Translating EVs-based therapy from bench to bedside remains challenging due to inefficient delivery of EVs to the injured area and lack of techniques to visualize the entire targeting process. Here we developed a dopamine surface functionalization platform that facilitates easy and simultaneous conjugation of targeting peptide and multi-mode imaging probes to the surface of EVs. Utilizing this platform we concurrently modified M2 microglia-derived EVs (M2-EVs) with neuronal targeting peptide rabies virus glycoprotein peptide 29 (RVG29) and multi-modal imaging tracers, resulting in the targeted delivery of M2-EVs to stroke mice brain and enabled the dynamic visualization of the targeting process from whole-body to cellular levels. We determined that intra-arterial injection achieved the highest efficiency of targeted delivery of engineered EVs to the stroke mice brain, improved therapeutic efficacy by reducing neuronal apoptosis. Mechanistically, EVs miRNA array revealed that a number of anti-apoptosis related miRNAs were significantly up-regulated, including miR-221-3p and miR-423-3p, both exerted anti-apoptotic effects through p38/ERK signalling pathways in stroke. Overall, this platform provides a facile and powerful tool for multifunctional engineering of EVs for multiscale therapeutic evaluation and enhancement of EV-based therapy, with valuable prospects for clinical translation.