In situ‐crosslinked Zippersomes enhance cardiac repair by increasing accumulation and retention

Mesenchymal stem cell (MSC)‐derived extracellular vesicles (EVs) are a promising treatment for myocardial infarction (MI), but their therapeutic efficacy is limited by inefficient accumulation at the target site. A minimally invasive MSC EV therapy that enhances EV accumulation at the disease site and extends EV retention could significantly improve post‐infarct cardiac regeneration. Here, we show that EVs decorated with the next‐generation of high‐affinity (HiA) heterodimerizing leucine zippers, termed HiA Zippersomes, amplify targetable surface areas through in situ crosslinking and exhibited ~7‐fold enhanced accumulation within the infarcted myocardium in mice after 3 days and continued to be retained up to Day 21, surpassing the performance of unmodified EVs. After MI in mice, HiA Zippersomes increase the ejection fraction by 53% and 100% compared with unmodified EVs and phosphate‐buffered saline (PBS), respectively. This notable improvement in cardiac function played a crucial role in restoring healthy heart performance. HiA Zippersomes also robustly decrease infarct size by 52% and 60% compared with unmodified EVs and PBS, respectively, thus representing a promising platform for minimally invasive vesicle delivery to the infarcted heart compared to intramyocardial injections.