In situ‐crosslinked <scp>Zippersomes</scp> 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.