The characteristics of sub 10 nm manganese oxide T1 contrast agents of different nanostructured morphologies.

There is continuous interest in developing manganese-based T(1) contrast agents. While much effort has been made to synthesize manganese chelates, the development of manganese-based nanoparticle, particularly manganese oxides, as MRI contrast agents is burgeoning. In this report, sub-10-nm nanospheres, nanoplates, and nanocubes of Mn(3)O(4) were synthesized and exhibited paramagnetic behavior at room temperature on the basis of superconducting quantum interference devices (SQUID) measurements. The surface Mn(3+) passivated nanoplates examined by x-ray photoelectron spectroscopy (XPS) had the largest r(1) relaxivity of the reported manganese oxide nanoparticles. The MR labeling assays of Mn(3)O(4) nanoplate-treated A549 lung cancer cells showed that MR signals increased to 139% in T(1)-weighted images compared with untreated cells when the Mn ion concentration went down to 1.3 x 10(-2) mM. A dark field illumination microscope was employed to monitor Mn(3)O(4) nanoplates internalized into cells as a function of time. Copyright 2010 Elsevier Ltd. All rights reserved.