title: Nano assembly and encapsulation; a versatile platform for slowing the rotation of polyanionic Gd(3+) -based MRI contrast agents.
abstract: Encapsulating discrete Gd(3+) chelates in nano-assembled capsules (NACs) is a simple and effective method of preparing an MRI contrast agent capable of delivering a large payload of high relaxivity imaging agent. The preparation of contrast agent containing NACs had previously focussed on preparations incorporating GdDOTP(5-) into the internal aggregate. In this report we demonstrate that other Gd(3+) chelates bearing overall charges as low as 2- can also be used to prepare NACs. This discovery opens up the possibility of using Gd(3+) chelates that have inner-sphere water molecules that could further increase the relaxivity enhancement associated with the long τR that arises from encapsulation. However, encapsulation of the q = 1 chelate GdDTPA(2-) did not give rise to a significant increase in relaxivity relative to encapsulation of the outer-sphere chelate GdTTHA(3-). This leads us to the conclusion that in the NAC interior proton transport is not mediated by movement of whole water molecules and the enhanced relaxivity of Gd(3+) chelate encapsulated within NACs arises primarily from second sphere effects.
authors.affiliation: Department of Chemistry, Portland State University, 1719 SW 10th Avenue, Portland, OR, 97201, USA.
authors.forename: Annah
authors.initials: A
authors.lastname: Farashishiko
authors.affiliation: Institute of Environmental Health, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR, 97239, USA.|Department of Chemistry, Reed College, 3203 SE Woodstock Blvd, Portland, OR, 97202, USA.
authors.forename: Kelly N
authors.initials: KN
authors.lastname: Chacón
authors.affiliation: Institute of Environmental Health, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR, 97239, USA.
authors.forename: Ninian J
authors.initials: NJ
authors.lastname: Blackburn
authors.affiliation: Department of Chemistry, Portland State University, 1719 SW 10th Avenue, Portland, OR, 97201, USA.|Advanced Imaging Research Center, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR, 97239, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Woods
mesh_terms: D002614:Chelating Agents / Q000737:chemistry; D003287:Contrast Media / Q000737:chemistry* / Q000627:therapeutic use; D019786:Gadolinium DTPA / Q000737:chemistry* / Q000627:therapeutic use; D006801:Humans; D008279:Magnetic Resonance Imaging; D053769:Nanocapsules / Q000737:chemistry* / Q000627:therapeutic use; D053758:Nanoparticles / Q000737:chemistry / Q000627:therapeutic use; D000071228:Polyelectrolytes; D011108:Polymers / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D002614:Chelating Agents; D003287:Contrast Media; D019786:Gadolinium DTPA; D053769:Nanocapsules; D000071228:Polyelectrolytes; D011108:Polymers; D012822:Silicon Dioxide; D014867:Water
keywords: MRI contrast agent; large payload delivery; nano-encapsulation