Smart composite hydrogel with magnetocaloric anisotropy for controllable multi-drug release

Controllable multi-drug release has been achieved by constructing a unique composite hydrogel structure comprising two layers of agar hydrogel, each incorporated with magnetically aligned anisotropic Fe3O4 nano-rods. With the orthogonal alignment of the Fe3O4 nanorods chains in the two layers, controllable multi-drug release can be triggered by the magnetocaloric anisotropy in different layers of the composite hydrogel, depending on the direction of the external alternating magnetic field. The thermal-triggered release of methylene blue (MB) increases up to 1.4 folds by switching magnetic field direction from 0 degrees to 90 degrees. The physical origin of magnetocaloric anisotropy is magnetic anisotropy. The as-designed composite hydrogel displays an obvious opposite drug release trend by switching the magnetic field direction from 0 degrees to 90 degrees. This opposite drug release trend maintains significantly after more than 4 times of magnetic field direction switching. This work opens a promising avenue for realizing the combination of magnetic hyperthermia and remotely controllable multi-drug combination therapy.