Gary Zabow

Controlled transport of magnetic particles using soft magnetic patterns

Inspired by magnetic bubble memory technology, we demonstrate the temporal and spatial manipulation of superparamagnetic beads guided by soft magnetic patterns in a rotating magnetic field. Soft magnetic structures allow complex and repetitive tasks to be performed. As a demonstration, we show cyclic capture and release of antibodies from different microfluidic streams.

Large T 1 contrast enhancement using superparamagnetic nanoparticles in ultra-low field MRI

Superparamagnetic iron oxide nanoparticles (SPIONs) are widely investigated and utilized as magnetic resonance imaging (MRI) contrast and therapy agents due to their large magnetic moments. Local field inhomogeneities caused by these high magnetic moments are used to generate T2 contrast in clinical high-field MRI, resulting in signal loss (darker contrast). Here we present strong T1 contrast enhancement (brighter contrast) from SPIONs (diameters from 11u2009nm to 22u2009nm) as observed in the ultra-low field (ULF) MRI at 0.13 mT. We have achieved a high longitudinal relaxivity for 18u2009nm SPION solutions, r1u2009=u2009615u2009s−1 mM−1, which is two orders of magnitude larger than typical commercial Gd-based T1 contrast agents operating at high fields (1.5xa0T and 3xa0T). The significantly enhanced r1 value at ultra-low fields is attributed to the coupling of proton spins with SPION magnetic fluctuations (Brownian and Néel) associated with a low frequency peak in the imaginary part of AC susceptibility (χ”). SPION-based T1-weighted ULF MRI has the advantages of enhanced signal, shorter imaging times, and iron-oxide-based nontoxic biocompatible agents. This approach shows promise to become a functional imaging technique, similar to PET, where low spatial resolution is compensated for by important functional information.

Author Correction: Large T 1 contrast enhancement using superparamagnetic nanoparticles in ultra-low field MRI

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Multispectral MR Imaging and Sensing Using Shaped Nanoparticles

The idea that size and shape can determine color is well known in optics-based quantum dot and plasmonic nanoparticle fields. But what about in the radio-frequency (RF) portion of the spectrum? This chapter reviews recent work on specially shaped magnetic nanostructures that shift the nuclear magnetic resonance (NMR) frequency of surrounding water, effectively using shape to control the RF “color” of an NMR signal. Operational principles behind these RF analogs to multicolor optical nanoparticles are explained, showing how particle shape can add new multispectral content to magnetic resonance imaging (MRI) and comparing these shaped nanoparticles to conventional MRI contrast agents. Magnetic structures that can dynamically vary their shape in response to local conditions are also discussed and their potential as NMR-readable RF “colorimetric” nanoprobes considered.

Microfabricated multispectral MRI agents: A brief overview

This paper provides an introductory overview of recent microfabricated, as opposed to traditional chemically synthesized, magnetic resonance imaging (MRI) contrast agents. As a specific example of the enhanced agent functionality that top-down micro-engineering allows, the paper focuses on recently demonstrated magnetic microstructures that provide multispectral MRI contrast.