Polydopamine-assisted architecture-enabled local delivery of miR-34a-loaded M1 macrophage extracellular vesicles and curcumin from an injectable thermogelling hydrogel for triple-negative breast cancer

Triple-negative breast cancer (TNBC) remains difficult to treat because of its aggressive phenotype, limited targetable pathways, and the need for local delivery systems that improve therapeutic retention without compromising cargo integrity. In this study, we engineered an injectable preorganized local dual-cargo delivery platform in which miR-34a-loaded M1 macrophage-derived extracellular vesicles (miR-34a@M1EVs) were immobilized onto polydopamine-coated curcumin-loaded poly(D,L-lactide-co-glycolide) microspheres and embedded within a thermogelling chitosan/β-glycerophosphate/hyaluronic acid hydrogel. The central objective was to determine whether this preorganized EV-on-microsphere architecture provides a measurable advantage over simple co-embedding of the same cargos in the same hydrogel matrix. M1 polarization was confirmed before EV isolation, and miR-34a loading substantially enriched vesicular cargo while preserving EV morphology, size distribution, and marker retention. Curcumin-loaded microspheres maintained structural integrity after polydopamine treatment, with convergent morphology- and physicochemical evidence supporting surface modification. Polydopamine-assisted assembly improved EV association and persistence on microspheres under both PBS and serum challenge. The final hydrogel remained injectable, thermogelled near physiological temperature, and preserved depot-forming behavior after cargo incorporation. Relative to free cargos, non-hydrogel controls, and the simple co-embedded hydrogel comparator, the engineered preorganized hydrogel showed stronger overall retention of both miR-34a and curcumin, higher intracellular miR delivery in MDA-MB-231 cells, greater suppression of viability and clonogenicity, stronger apoptosis and G0/G1 cell-cycle redistribution, lower residual invasion, and deeper downregulation of BCL2, SIRT1, and NOTCH1, while remaining comparatively well tolerated in MCF-10A cells. Collectively, these findings support a chemically integrated, architecture-based strategy for improving localized dual-cargo delivery against TNBC cells in vitro , while suggesting that the observed advantage reflects the combined effects of interfacial preorganization and improved depot-level cargo retention.