A click-crosslinked dopamine-functionalized hydrogel for therapeutic delivery of stem cell-derived extracellular...

Stem cell-derived extracellular vesicles (EVs) hold significant promise for tissue regeneration due to their potent therapeutic cargo. However, their clinical translation is hindered by rapid clearance from target sites following systemic or local administration, leading to inefficient delivery and limited therapeutic efficacy. To overcome this critical challenge, we developed a click-crosslinked dopamine-functionalized hyaluronic acid hydrogel system (Dopa-HA) for the sustained and localized delivery of EVs. Dopamine was chemically conjugated to the click-crosslinked hydrogel to enhance the robust immobilization of EVs. The physicochemical properties of this hydrogel system were subsequently characterized, including dopamine functionalization degree, rheological behavior, degradation rates, and in vitro protein release profiles. Our investigations revealed that Dopa-HAs (4% and 14%) enable controlled release of model proteins (albumin and cholesterol), with release kinetics directly tunable through adjustments in the degree of dopamine functionalization. Particularly, when loaded with osteogenic stem cell-derived EVs, the Dopa-HA significantly accelerated the osteogenic differentiation of encapsulated stem cells in vitro. In vivo study in a rat calvarial defect model demonstrated that Dopa-HA markedly enhanced bone regeneration, with Dopa-HA-EV constructs achieving nearly twofold faster defect filling than HA-EV controls. Biodistribution analysis of fluorescently labeled EVs further revealed prolonged local retention at the defect site for up to 10 days post-implantation. This dopamine-functionalized hydrogel platform represents a significant advancement, effectively addressing the challenge of EV delivery by extending their local availability and thereby augmenting therapeutic outcomes.