Magnetically Induced Anisotropic Microstructures on Polyethylene Glycol Hydrogel Facilitate BMSC Alignment and Osteogenic Differentiation

Many tissues exhibit structural anisotropy, which imparts orientation-specific properties and functions. However, recapitulating the cellular patterns found in anisotropic tissues presents a remarkable challenge, particularly when using soft and wet hydrogels. Herein, we develop self-assembled anisotropic magnetic Fe₃O₄ micropatterns on polyethylene glycol hydrogels utilizing dipole-dipole interactions. Under the influence of a static magnetic field, Fe₃O₄ nanoparticles align into highly ordered structures with a height of 400-600 nm and a width of 8-10 μm. Furthermore, our layer-by-layer assembly technique enables the creation of oriented micropatterns with varying densities and heights, which can be further manipulated to form three-dimensional structures by adjusting the angle of the magnetic field. These anisotropic magnetic Fe₃O₄ micropatterns can be applied to various substrates, including treated glass slides, standard glass slides, silicon wafers, and polydimethylsiloxane. The patterned Fe₃O₄ scaffolds, modified with gold coating, effectively enhance cellular adhesion, orientation, and osteogenic differentiation of bone marrow-derived stem cells, which is crucial for effective tissue repair. Overall, this study presents an efficient strategy for constructing anisotropic Fe₃O₄ micropattern hydrogels, providing a bioactive platform that significantly enhances cellular functions.