Injectable Macroporous Ferrogel Microbeads with a High Structural Stability for Magnetically Actuated Drug Delivery.

Macroporous hydrogels are an attractive material platform that can provide shortened interfacial diffusion pathways and high biomacromolecule loading. Recently, macroporous ferrogels have shown high potential for use in the on-demand delivery of bioactive molecules, resulting from their reversible and large volumetric deformation upon magnetic stimulation. However, these macroporous ferrogels require surgical placement in the body due to their large size; an injectable form of macroporous ferrogels has not yet been reported. In this study, injectable macroporous ferrogel microbeads loaded with iron oxide nanoparticles have been prepared on the basis of alginate microbeads for on-demand drug release. A simple solvent exchange and subsequent covalent cross-linking of the alginate chains in hydrogel microbeads induced a high polymer density on the hydrogel network and led to enhanced mechanical properties even after the generation of macropores in the microbeads. The macroporous ferrogel microbeads exhibited good mechanical stability and were stable during needle injection. The increased loading of large biomolecules due to the macroporosity of the microbeads and their large reversible volumetric deformation response to the external magnetic field enabled their potential for use in the on-demand delivery of drugs of assorted sizes by magnetic actuation. As a result of their structural stability, injectable size, and ability for on-demand drug delivery, ferrogel microbeads have promising potential for application in many biomedical fields.