Nano assembly and encapsulation; a versatile platform for slowing the rotation of polyanionic Gd3+‐based MRI contrast agents

In this report we demonstrate that other Gd3+ chelates bearing overall charges as low as 2‐ can also be used to prepare NACs. This discovery opens up the possibility of using Gd3+ 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 GdDTPA2‐ did not give rise to a significant increase in relaxivity relative to encapsulation of the outer‐sphere chelate GdTTHA3‐. 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 Gd3+ chelate encapsulated within NACs arises primarily from second sphere effects. Copyright © 2015 John Wiley & Sons, Ltd. Nano‐assembled capsules (NACs) can be used to deliver large payloads of high relaxivity Gd3+‐based contrast agent; a potential solution to the problem of high contrast agent detection limits in MRI. NACs can be formed with a range of polyanionic Gd3+ chelates if the overall chelate charge 2‐ or more negative. Examination of the effect of this encapsulation on mono‐hydrated and non‐hydrated Gd3+ chelates reveals that proton, rather than whole water, transfer is the key mechanism of action in these systems.
Source: Contrast Media and Molecular Imaging - Category: Radiology Authors: Tags: Full paper Source Type: research