Assessing the Behavior of Nanoparticles in Biotechnological and Environmental Systems with MRI

The increasing application of nanoparticles in consumer products and industry inevitably contributes to their release into the global water cycle as pollutants¹. The nanoparticles' fate in technical and environmental systems is crucial with respect to the potential harm for ecosystems and human beings. Super paramagnetic iron oxide nanoparticles (SPION) are often applied in fundamental research as well as in biomedicine as contrast agents in Magnetic Resonance Imaging (MRI) for therapy, diagnostics and system characterization². In the field of environmental science, the application of SPION can help to investigate the behavior and fate of nanoparticles³. In this study differently coated and sized SPION were applied as model compounds to trace the nanoparticles' behavior in two different environmental systems: (1) Investigation of the interaction and transport of nanoparticles in technical biofilms from wastewater treatment and (2) Investigation of the mobility of nanoparticles in a water-saturated porous medium. Study (1) revealed that the interactions between SPION and the heterogeneous biofilm requires hours until penetration occurs. The sorption mainly occurred at the outer biofilm layers (Figure 1). The penetration depth in the biofilm depends on the particle size, and the sorption is irreversible after 14 d of exposure emphasizing that contact time matters. For inorganic porous media (2) MRI allowed a detailed visualization of the distribution patterns of SPION in the column. SPION mobility especially depends on the SPION surface properties (Figure 1)⁴. The approach of using MRI leads to a detailed observation of nanoparticle transport in environmental and technical systems and provides experimental information about mass flows needed for simulations.

(1) Sorption of SPION (25 nm) on biofilms used in wastewater treatment. (2) Distribution of SPION retention (20 nm) in a water-saturated porous medium at a Darcy velocity of 14.5 m/d.