Experimental and Simulative Characterization of a Hybrid Magnetic Array for Steering Superparamagnetic Nanoparticles in Drug Targeting

Adjustable magnetic fields are essential for precisely steering drug-loaded magnetic nanoparticles in cancer therapy. Since electromagnets require high currents to achieve a strong magnetic force, this paper presents a new approach combining electromagnets and permanent magnets. The basic idea of the hybrid array is to use the strong and low-cost magnetic field of permanent magnets and superimpose them with the field of electromagnets via a Halbach arrangement. This results in a constructive and destructive superposition of the magnetic field, which can easily be reversed by the applied current's direction. Moreover, the current's magnitude can be reduced dramatically to 2 A, as the primary magnetic flux comes from the permanent magnets. To the authors' knowledge, this is the first paper proposing a magnetic hybrid array for steering magnetic nanoparticles in a velocity flow. The array was validated in simulations using COMSOL Multiphysics and measurements in a tube flow system. In contrast to state-of-the-art publications, the particle distribution was determined quantitatively. In this proof of concept, the simulation and measurement results fit well. It was demonstrated that the magnetic force is adjustable via the current and that the magnetic field of permanent magnets can be eliminated by superimposing the field of electromagnets, also indicated by the particle distribution. Furthermore, gravitation has a significant influence on particle distribution. The proposed system combines the advantages of permanent magnets and electromagnets. Hence, the induced heat that damages tissue is decreased, which is crucial for bringing the setup into clinical treatments.