However, biological studies uncovered subtle differences at the local level, showing that hydrogels crosslinked with NPs promoted better spreading and differentiation of encapsulated stem cells and indicating their better suitability for cell-based bone regenerative therapy. The covalent modification of GelMA with vinyl-coated iron oxide NPs was another method to control material stiffness and indirectly promote cartilage regeneration by influencing the behavior of cells (e.g., chondrocytes, bone marrow-derived stem cells (BMSC)) that enter into contact with the hybrid hydrogel. permission. Copyright 2021 Elsevier.