Development of an injectable alginate-collagen hydrogel for cardiac delivery of extracellular vesicles

•An alginate-collagen hydrogel (HG) was developed as an extracellular vesicle (EV) delivery system for increasing EV exposure in the heart after myocardial infarction (MI).•The combination of alginate and collagen allowed for the development of an in-situ jellifying HG compatible with EV delivery via catheter-based technology.•The HG developed possessed an internal gel structure, weak mechanical properties and low viscosity, facilitating easy administration.•The alginate-collagen HG showed long-term retention in the heart and allowed sustained release of EVs for at least 7 days in a rat model of MI.