Harnessing Gradient Topography and Dual-Mode Bioactive Delivery via Bone-Adhesive Exosome Mimetics for Rotator Cuff...

Rotator cuff repair frequently fails because the native enthesis relies on a continuous structural and compositional transition from tendon to bone. Here, we present an enthesis-mimetic, dual-gradient scaffold that couples a continuous random-to-aligned fiber orientation gradient with graded hydroxyapatite mineralization and quercetin-loaded, alendronate-conjugated exosome mimetics (EMQ^A) for spatially programmed healing. A modified electrospinning collector locally modulated the electric field to generate the orientation gradient in a single deposition process, followed by region-dependent mineralization to create a tunable apatite interface. EMQ^A was engineered via bioorthogonal chemistry and immobilized on the mineralized scaffold through alendronate-hydroxyapatite affinity, enabling mineral-dependent retention and presentation. In vitro, the platform elicited region-selective lineage responses, with enhanced osteogenic signaling on the mineral-rich random region and chondrogenic/tenogenic-associated profiles on the aligned region, accompanied by differential RUNX2 nuclear localization. In a preclinical rotator cuff repair model, the dual-gradient mineralized PCL/silk/quercetin (PSQ) scaffold with EMQ^A immobilization (PSQm@EMQ^A) scaffold promoted improved mineralized tissue formation by micro-CT, more organized interface remodeling with increased osteogenic/fibrocartilaginous markers, reduced lipid deposition at the repair site, and superior mechanical performance compared with controls. This work establishes a scalable strategy to integrate structural gradients with mineral-affinitive bioactive delivery to recreate enthesis-like microenvironments and enhance tendon-to-bone healing.