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

Abstract

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(γ-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 μg mL⁻¹). The relatively high r₂ 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.