Facile assembly of Fe3O4@Au nanocomposite particles for dual mode magnetic resonance and computed tomography imaging applications

We report a facile approach for fabrication of Fe3O4@Au nanocomposite particles (NCPs) as a dual mode contrast agent for both magnetic resonance (MR) and computed tomography (CT) imaging applications. In this study, Fe3O4 nanoparticles (NPs) prepared by a controlled coprecipitation approach were used as core particles for subsequent electrostatic layer-by-layer (LbL) assembly of poly(gamma-glutamic acid) (PGA) and poly(L-lysine) (PLL) to form PGA/PLL/PGA multilayers, followed by assembly with dendrimer-entrapped gold NPs (Au DENPs) formed using amine-terminated generation 5 poly(amidoamine) dendrimers as templates. After crosslinking the multilayered shell of PGA/PLL/PGA/Au DENPs via EDC chemistry, the remaining amine groups of the outermost layer of Au DENPs were acetylated to neutralize the surface charge of the particles. The formed Fe3O4@Au NCPs were well characterized via different techniques. We show that the formed Fe3O4@Au NCPs are colloidally stable, hemocompatible, and biocompatible in the given concentration range (0-100 mu g mL(-1)). The relatively high r(2) relaxivity (71.55 mM(-1) s(-1)) and enhanced X-ray attenuation property when compared with either the uncoated Fe3O4 NPs or the Au DENPs afford the developed Fe3O4@Au NCPs with a capacity not only for dual mode CT and MR imaging of cells in vitro, but also for MR imaging of liver and CT imaging of subcutaneous tissue in vivo. With the facile integration of both Fe3O4 NPs and Au DENPs within one particle system via the LbL assembly technique and dendrimer chemistry, it is expected that the fabricated Fe3O4@Au NCPs may be further modified with multifunctionalities for multi-mode imaging of various biological systems.