title: Effect of Competitive Surface Functionalization on Dual-Modality Fluorescence and Magnetic Resonance Imaging of Single-Walled Carbon Nanotubes.
abstract: It is well-known that ionic surfactant coated single-walled carbon nanotubes (SWNTs) possess higher near-infrared fluorescence (NIRF) quantum yield than nonionic polymer functionalized SWNTs. However, the influence of surface functionalization on the magnetic properties of SWNTs forT2-weighted magnetic resonance imaging (MRI) has not been reported. Here, we demonstrate that SWNTs functionalized by nonionic polymers display superiorT2relaxivity for MRI as compared to those coated by ionic surfactants. This difference may indicate that micelle structures formed by ionic surfactants are sufficiently tight to partially exclude water protons from the iron catalysts attached to the ends of SWNTs. On the basis of the different effects of the two types of suspension agents on NIRF and MRI of functionalized SWNTs, we further explore the competitive surface functionalization between ionic surfactants and nonionic polymers by stepwise replacing ionic surfactant molecules in a nanotube suspension with nonionic polymers. The superior NIRF of ionic surfactant coated SWNTs gradually quenches whereas no improvement onT2relaxivity is observed during this replacement process. This result may indicate that nonionic polymers wrap around the outside of micelle structures to form small nanotube bundles rather than replacing ionic surfactants in the micelle structures to directly interact with the SWNT surface. Finally, we demonstrate the feasibility of dual-modality NIRF and MRI of nonionic polymer functionalized SWNTs in brain cells.
authors.affiliation: Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, Tennessee 37235, United States.
authors.forename: Tu
authors.initials: T
authors.lastname: Hong
authors.affiliation: Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, United States.
authors.forename: Roman M
authors.initials: RM
authors.lastname: Lazarenko
authors.affiliation: Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee 37232, United States.
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Colvin
authors.affiliation: Interdisciplinary Program in Materials Science, Vanderbilt University, Nashville, Tennessee 37235, United States.
authors.forename: Roel L
authors.initials: RL
authors.lastname: Flores
authors.affiliation: Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, United States.
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, Tennessee 37235, United States ; Interdisciplinary Program in Materials Science, Vanderbilt University, Nashville, Tennessee 37235, United States ; Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, United States.
authors.forename: Ya-Qiong
authors.initials: YQ
authors.lastname: Xu