Monodisperse and Size-Tunable Alginate Microspheres Encapsulating Fe ₃ O ₄ Nanoparticles via Flow Focusing Microfluidics

Magnetically responsive drug-loaded microspheres enable precision drug delivery under the guidance of an external magnetic field, which can significantly elevate the drug concentration at lesional sites and thus serve as a crucial research direction in the fields of nanomedicine and materials science. In this study, sodium alginate/Fe3O4 composite microspheres were fabricated via the flow-focusing microfluidics approach. The microspheres exhibit excellent size tunability (34–80 μm) by adjusting the two-phase pressure ratio, outstanding monodispersity with a coefficient of variation ≤5.44%, along with superparamagnetism and a rapid magnetic response. The microspheres effectively encapsulated highly water-soluble nicotinamide (94.9% efficiency) and provided a controlled, sustained release without initial burst. As biocompatible and eco-friendly magnetic carriers, these microspheres provide a promising platform for medical applications such as targeted drug delivery and magnetic hyperthermia.