Man-made iron oxide nanoparticles have widespread importance for labeling cells and molecules both inside and outside the human body. Besides synthetic particles, many organisms also generate naturally occurring iron oxide nanoparticles, known as ferritin, to store and regulate iron within their bodies. Whether man-made or natural, these iron oxide nanoparticles have a magnetization that can be used as a tool for manipulation or sensing in biological environments. However, nanoparticles often aggregate in complex bio-environments, and the effect of aggregation on their collective magnetic properties is not well understood. The overall objective of this work is to explore the relationship between nanoparticle clustering and resultant magnetic properties. Findings from this work can be potentially used to engineer magnetism-based sensing tools for more accurately tracking iron nanoparticles in biological systems. Data from this project can also advance other biomedical applications of iron oxide particles, such as their uses in magnetic hyperthermia for cancer therapy or as contrast agents for medical imaging. Besides advancing the field of bio-magnetism and nano-biotechnology, this research project will help train the next generation of scientists and engineers by providing research experience to students in state-of-the-art techniques for synthesis and characterization of nanoparticles, by enhancing infrastructure for research and education through the development of new techniques for magnetic characterization and by broadening participation of underrepresented groups in science and engineering activities.

Iron-oxide nanoparticles have become crucial tools in biomedicine and bio-nanotechnology due to their magnetic behavior. These include synthetic magnetite nanoparticles (~5 to 10 nm in diameter), and naturally occurring ferrihydrite core (~ 5 to 8 nm) present in ferritin, the largest iron-storage protein in the human body. Determining the spatial localization and quantification of these iron-oxide nanoparticles in cells and tissues is critical for a number of applications in health. Thus far our ability to characterize the spatial distribution and quantity of iron oxide nanoparticles is limited to biochemical approaches like histochemical staining, which are largely qualitative. Magnetically sensitive detection offers an alternative, non-destructive, label free and quantitative means for characterization of iron-oxide nanoparticles. However, in biological systems, nanoparticles are often found in aggregates/clusters, which can impact their local and global magnetic properties and complicate interpretation of magnetic signals. The goal of this project is to understand how clustering of bio-inspired iron-oxide nanoparticles affect their magnetic properties across many length scales (nanometer to micrometer scale). Specifically, interactions between individual particles, as well as between larger clusters of particles, will be studied using a range of magnetically sensitive techniques. Biologically derived clusters of particles as well as artificially engineered aggregates will be used for the study. These include synthetic magnetite nanoparticles and naturally occurring ferrihydrite cores present in ferritin. In some cases, clusters will be nanofabricated using template guided assembly, so that geometric parameters of clusters such as size, shape, and interparticle distance can be varied systematically. Characterization of particle assemblies will be performed using techniques such as analytical electron microscopy, magnetic force microscopy, super-conducting quantum interference device magnetometry and magnetic resonance imaging. Results from this study will be used to develop advanced, magnetism-based metrology for localizing and quantifying aggregates of iron oxide nanoparticles in biological environments. An understanding of the effect of clustering on magnetic properties can enable quantitative histo-magnetic detection schemes for mapping iron deposits in tissue sections. The project activities will be accomplished by providing multidisciplinary and inter-institutional research experiences for graduate and undergraduate students and by establishing new research collaborations. The project will also include outreach efforts to broaden participation, by developing and offering hands-on workshops on engineering concepts to under-privileged middle school students at a local school.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

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Ohio State University
United States
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