Real-time analysis of magnetic nanoparticle clustering effects by inline-magnetic particle spectroscopy

The requirements for magnetic nanomaterials in life science strongly differ depending on the envisaged specific biomedical application. Especially, the magnetic properties of magnetic nanoparticles might - often unintended - change depending on their microscopic physiological environment with the consequence that the performance is reduced for the application. This frequently occurs if magnetic nanoparticles get internalized within distinct physiological entities in an organism due to immobilization or aggregation. As a consequence, magnetic nanoparticles obtain further surface modifications after synthesis to maintain the magnetic properties. Magnetic particle spectroscopy (MPS) is a fast, sensitive measurement technique that probes the dynamic magnetic response of MNP to a sinusoidal magnetic excitation and is very sensitive to detect changes of the local environment of MNP. In this study, we present the capability of inline-MPS to sensitively monitor the level of colloidal stability of electrostatically stabilized nanomaterials against saline-driven aggregation and to validate the successful aggregation prevention of particles by additional coating. Inline-MPS is a valuable technique for process monitoring as well as for investigating, supporting, and predicting the MNP behavior in biological environments.