The role and mechanism of magnetic hydrogels in bone diseases

Magnetic hydrogels are emerging as intelligent biomaterials that integrate superparamagnetic nanoparticles into hydrogel networks. Under external magnetic fields, they enable remotely controlled targeted delivery, mechanical stimulation, and thermal regulation, offering a strategy for treating bone diseases. This review outlines the construction of magnetic hydrogels and their regulatory mechanisms. At the cellular level, magnetic hydrogels have been associated with several study–specific signaling responses that regulate osteogenic differentiation, macrophage polarization, stem–cell fate, and chondrocyte metabolism. The strength of evidence supporting these mechanisms varies: some pathways are supported by pathway specific molecular assays or pharmacological perturbation, whereas others remain mechanistic hypotheses inferred from established biological knowledge. Simultaneously, these hydrogels guide the differentiation of mesenchymal stem cells and chondrocytes by adjusting the physicochemical microenvironment. In disease models, magnetic hydrogels show integrated therapeutic potential across osteoarthritis, osteosarcoma, fractures, and bone defects, including inflammation modulation, combination tumor therapy, sequential drug release, and defect repair. We further discuss the remaining challenges for clinical translation, including long–term biosafety, magnetic field standardization, manufacturing reproducibility, and structure–property–performance relationships.