Wilson, Lon J.2012-07-032012-07-032011-052011Ananta Narayanan, Jeyarama Subramanian. "Carbon-Based Nanostructures as Advanced Contrast Agents for Magnetic Resonance Imaging." (2011) Diss., Rice University. <a href="https://hdl.handle.net/1911/64375">https://hdl.handle.net/1911/64375</a>.https://hdl.handle.net/1911/64375Superparamagnetic carbon-based nanostructures are presented as contrast agents (CAs) for advanced imaging applications such as cellular and molecular imaging using magnetic resonance imaging (MRI). Gadolinium-loaded, ultra-short single-walled carbon nanotubes (gadonanotubes; GNTs) are shown to have extremely high rl relaxivities (contrast enhancement efficacy), especially at low-magnetic field strengths. The inherent lipophilicity of GNTs provides them the ability to image cells at low magnetic field strength. A carboxylated dextran-coated GNT (GadoDex) has been synthesized and proposed as a new biocompatible high-performance MRI CA. The rl relaxivity is ca. 20 times greater than for other paramagnetic Gd-based CAs. This enhanced relaxivity for GadoDex is due to the synergistic effects of an increased molecular tumbling time ('tR) and a faster proton exchange rate ('tm). GNTs also exhibit very large transverse relaxivities (r2) at high magnetic fields ~ 3 T). The dependence of the transverse relaxation rates (especially R2 *) of labeled cells on GNT concentration offers the possibility to quantify cell population in vivo using R2 * mapping. The cell-labeling efficiency and high transverse relaxivities of GNTs has enabled the first non-iron oxide-based single-cell imaging using MRI.100 ppapplication/pdfengCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.ChemistryThesisAnantaNTHESIS CHEM. 2011 ANANTA NARAYANAN