title: Magnetic Nanoclusters with Hydrophilic Spacing for Dual Drug Delivery and Sensitive Magnetic Resonance Imaging.
abstract: Magnetic Block Ionomer Clusters (MBIClusters) with hydrophilic ionic cores and nonionic coronas have been prepared that have ultrahigh transverse NMR relaxivities together with capacities for incorporating high concentrations of polar antibiotic payloads. Magnetite-polymer nanoparticles were assembled by adsorbing the polyacrylate block of an aminofunctional poly(ethylene oxide-b-acrylate) (H2N-PEO-b-PAA) copolymer onto magnetite nanoparticles. The PEO blocks extended into aqueous media to keep the nanoparticles dispersed. Amines at the tips of the H2N-PEO corona were then linked through reaction with a PEO diacrylate oligomer to yieldMBIClusterswhere the metal oxide in the precursor nanoparticles were distinctly separated by the hydrophilic polymer. The intensity average spacing between the magnetite nanoparticles within the clusters was estimated to be ~50 nm. TheseMBIClusterswith hydrophilic intra-cluster space had transverse relaxivities (r2's) that increased from 190 to 604 s-1mM Fe-1measured at 1.4 T and 37 °C as their average sizes increased. The clusters were loaded with up to ~38 wt% of the multi-cationic drug gentamicin. MRI scans focused on the livers of mice demonstrated that theseMBIClustersare sensitive contrast agents.
authors.affiliation: Macromolecules and Interfaces Institute, Virginia Tech, Blacksburg, VA.
authors.forename: Nipon
authors.initials: N
authors.lastname: Pothayee
authors.affiliation: Macromolecules and Interfaces Institute, Virginia Tech, Blacksburg, VA.
authors.forename: Sharavanan
authors.initials: S
authors.lastname: Balasubramaniam
authors.affiliation: Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disease and Stroke, National Institutes of Health, Bethesda, MD.
authors.forename: Nikorn
authors.initials: N
authors.lastname: Pothayee
authors.affiliation: VA-MD School of Veterinary Medicine, Virginia Tech, Blacksburg, VA.
authors.forename: Neeta
authors.initials: N
authors.lastname: Jain
authors.affiliation: Macromolecules and Interfaces Institute, Virginia Tech, Blacksburg, VA.
authors.forename: Nan
authors.initials: N
authors.lastname: Hu
authors.affiliation: Macromolecules and Interfaces Institute, Virginia Tech, Blacksburg, VA.
authors.forename: Yinnian
authors.initials: Y
authors.lastname: Lin
authors.affiliation: Macromolecules and Interfaces Institute, Virginia Tech, Blacksburg, VA.
authors.forename: Richey M
authors.initials: RM
authors.lastname: Davis
authors.affiliation: VA-MD School of Veterinary Medicine, Virginia Tech, Blacksburg, VA.
authors.forename: Nammalwar
authors.initials: N
authors.lastname: Sriranganathan
authors.affiliation: Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disease and Stroke, National Institutes of Health, Bethesda, MD.
authors.forename: Alan P
authors.initials: AP
authors.lastname: Koretsky
authors.affiliation: Macromolecules and Interfaces Institute, Virginia Tech, Blacksburg, VA.
authors.forename: J S
authors.initials: JS
authors.lastname: Riffle
keywords: MRI; block ionomer; contrast agent; magnetite; relaxivity