Biodegradable Core–Shell Magnetic Microrobots With High Cell Capacity for Precise Co-Delivery of Stem Cells and Bioactive Molecules

Cell-loaded magnetic microrobots hold promise for the targeted delivery of stem cells in tissue regeneration. However, achieving high cell-loading capacity alongside effective co-delivery of functional bioactive molecules remains a major challenge. Herein, we present a biodegradable magnetic microrobot featuring a core–shell architecture, designed to co-deliver stem cells and bioactive molecules. These microrobots are fabricated using a rotation-induced inertial focusing technique, which allows control over their size and morphology while significantly enhancing cell-loading capacity. The core, composed of a biodegradable magnetic microsphere (MMS), enables external magnetic navigation and sustained drug release, while the outer shell, formed by mesenchymal stem cells (MSCs), ensures therapeutic viability. The microrobots demonstrate robust magnetic maneuverability and spatial control even in complex and viscous environments. We validated their efficacy in both a rabbit in vivo model and an ex vivo human cartilage model, where co-delivery of MSCs and transforming growth factor-β1 (TGF-β) led to significant improvements in cartilage repair and functional tissue regeneration. This biodegradable core–shell microrobot offers a scalable, multifunctional platform for efficient co-delivery of cells and bioactive molecules, with strong potential for clinical translation in regenerative medicine.