Dendrimer-Assisted Formation of Fe3O4/Au Nanocomposite Particles for Targeted Dual Mode CT/MR Imaging of Tumors.

A unique dendrimer-assisted approach is reported to create Fe3O4/Au nanocomposite particles (NCPs) for targeted dual mode computed tomography/magnetic resonance (CT/MR) imaging of tumors. In this approach, preformed Fe3O4 nanoparticles (NPs) are assembled with multilayers of poly(γ-glutamic acid) (PGA)/poly(L-lysine)/PGA/folic acid (FA)-modified dendrimer-entrapped gold nanoparticles via a layer-by-layer self-assembly technique. The interlayers are crosslinked via 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide chemistry, the assembled Au core NPs are then used as seed particles for subsequent seed-mediated growth of Au shells via iterative Au salt reduction process, and subsequent acetylation of the remaining amines of dendrimers leads to the formation of Fe3O4/Au(n.)Ac-FA NCPs with a tunable molar ratio of Au/Fe3O4. It is shown that the Fe3O4/Au(n.)Ac-FA NCPs at an optimized Au/Fe3O4 molar ratio of 2.02 display a relatively high R2 relaxivity (92.67 × 10(-3) M(-1) s(-1)) and good X-ray attenuation property, and are cytocompatible and hemocompatible in the given concentration range. Importantly, with the FA-mediated targeting, the Fe3O4/Au(n.)Ac-FA NCPs are able to be specifically uptaken by cancer cells overexpressing FA receptors, and be used as an efficient nanoprobe for targeted dual mode CT/MR imaging of a xenografted tumor model. With the versatile dendrimer chemistry, the developed Fe3O4/Au NCPs may be differently functionalized, thereby providing a unique platform for diagnosis and therapy of different biological systems.