Simulation of the long-term fate of superparamagnetic iron oxide-based nanoparticles using simulated biological fluids.

To simulate the stability and degradation of superparamagnetic iron oxide nanoparticles (MNP) as part of their life cycle using complex simulated biological fluids. A set of 13 MNP with different polymeric or inorganic shell materials was synthesized and characterized regarding stability and degradation of core and shell in simulated biological fluids. All MNP formulations showed excellent stability during storage and in simulated body fluid. In endosomal/lysosomal media the degradation behavior depended on shell characteristics (e.g., charge, acid-base character) and temperature enabling the development of an accelerated stress test protocol. Kinetics of transformations depending on the MNP type could be established to define structure-activity relationships as prediction model for rational particle design.