Study of amine-functionalized and angular-shaped iron oxide nanoparticles for MR/fluorescence bimodal imaging applications

Abstract

A simple preparation of water well dispersible angular-shaped and amine-functionalized super-paramagnetic iron oxide nanoparticles (A-SPIONs) was reported in this paper. A-SPIONs was synthesized via heating iron (Ⅲ) acetylacetonate in a mixed solvents of polyethyleneglycol (PEG) and branched polyetheyleneimine (b-PEI) with vigorous stirring. Both PEG and b-PEI provided high water dispersibility by competitive surface coating of A-SPIONs. In addition, b-PEI controlled overall morphologies of A-SPIONs to produce polyhedral nanocrystals with the aid of added halide ions and supplied active amine ends. Due to the amine functional group arising from b-PEI, the A-SPIONs were proved to have both positively charged surface (+29.1mV) and active sites which enable facile functionalization. By using A-SPIONs of 9.42 ± 2.93 nm (TEM observation), a high saturation magnetization value of 75.61 emu/g was measured using superconducting quantum interface device (SQUID). The A-SPIONs sustained stable dispersion in aqueous media with various pH, and their hydrodynamic size was about 13.97 nm in 0.10 M NaCl solution. Through MTT assay, the A-SPIONs were proved to have negligible cellular toxicity in SKOV-3, U87-MG and U251 cell lines. The angular-shaped iron oxide nanoparticles also exhibited high relaxivity for magnetic resonance imaging (MRI) originated from the high magnetization. Cy 5.5 dye-functionalized A-SPIONs (Cy5.5@A-SPIONs) were prepared and serial experiments were conducted to investigate fluorescence imaging applications. According to these results, the A-SPIONs are expected to have potentials in bimodal imaging application.