Magnetic Particle Spectroscopy to Determine the Magnetic Drug Targeting Efficiency of Different Magnetic Nanoparticles in a Flow Phantom

This paper describes an in vitro method to characterize the efficiency of a setup for magnetic drug targeting. The simple flow phantom includes a peristaltic pump propelling a magnetic nanoparticle (MNP) suspension through a tubing system. A magnet placed at a specific location at the tubing retained particles due to magnetic forces. The accumulated MNP concentration was quantified using magnetic particle spectroscopy (MPS) allowing the detection of small changes in MNP concentration. The system was tested with MNPs of three different mean hydrodynamic diameters suspended in bovine serum albumin and blood. We found a retention yield crucial depending on the hydrodynamic diameter. For MNPs with 50 nm mean hydrodynamic diameter no retention was observed, whereas MNPs with a mean hydrodynamic diameter of 330 nm were accumulated most efficiently, but already showed a slight aggregation tendency. In addition to the quantification of MNP retention, MPS allowed the detection of changes in size distribution as a consequence of the targeting process. These changes were confirmed in more detail using magnetorelaxometry.