Research
Magnetic Particles and听Biosensors
Magnetic Particle Synthesis and Characterization. I have an interest in creating magnetic nano- and micro- particles for听applications as biomedical imaging agents and sensors.
RF-Addressable Smart Biosensors for MRI.听In previous work, at the National Institute of Standards and Technology (NIST) and听collaborators in the showed that magnetic particles with special shapes could be used as and . One of the special geometries is a magnetic particle shaped like a .听
I have听been developing听a that can be produced cheaply using a soft lithographic technique known as micro-molding. Some of these particles are shown in the image on the right (displayed next to a single grain of salt to provide a sense of scale). The particles have a cylindrical-shell geometry that encodes a unique RF signature听and can be made of a 鈥渟mart鈥 polymer that changes shape in response to specified environmental conditions, such as pH. The shape change causes a听corresponding,听quantifiable shift in the RF-frequency and reports on the microenvironment. This shift is much larger than standard nuclear magnetic resonance (NMR) chemical shifts, producing an unambiguous signal for sensing.听
Magnetic Mapping of Bio-Inspired Clusters of Iron Oxide Nanoparticles
In collaboration with听 at The Ohio State University (OSU), I have been exploring the magnetic properties of magnetic nanoparticle aggregates. Man-made iron oxide nanoparticles have widespread importance for labeling cells and molecules. 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. For this project, I am developing methods to micropattern nanoparticle aggregates with well-defined structural properties. The structure can then be correlated with magnetic force microscopy measurements performed by collaborators at OSU.
Findings can be potentially used to engineer magnetism-based tools for听tracking iron nanoparticles in biological systems. Also, understanding of the effect of clustering on magnetic properties can enable .
Nanomagnetism in Polymer Systems
Magentic Resonance Imaging (MRI).听MRI听is well-known as a medical imaging technique, but it can also be used to image materials systems. With collaborators at NIST, I showed that within a hydrogel network during听in situ听coprecipitation. The synthesis creates a magnetic nanoparticle-loaded polymer gel, or magnetogel. During听in situ听coprecipitation, iron oxide nanoparticles nucleate and grow due to diffusion of a precipitating agent throughout an iron precursor-loaded polymer network. The creation of iron oxide particles changes the magnetic properties of the gel, allowing the synthesis to be monitored听via听magnetic measurements. Formation of iron oxide nanoparticles generates dark, or hypointense, contrast in gradient echo (GRE) images acquired by MRI, allowing nanoparticle nucleation to be tracked in both space and time. This work was featured on the cover of Soft Matter (right).
Neutron Scattering. Polarized neutron scattering uses the magnetic moment of neutrons to map magnetization in physical systems down to angstroms. Recently, I have used听, which is the relationship between strain and magnetization, in stretched magnetic nanoparticle-polymer composites. This work was done with collaborators at the .
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