One pot synthesis of amine-functionalized and angular-shaped superparamagnetic iron oxide nanoparticles for MR/fluorescence bimodal imaging application

Abstract

Herein, we report the simple preparation of water dispersible angular-shaped amine-functionalized super-paramagnetic iron oxide nanoparticles (A-SPIONs). A-SPIONs were synthesized by heating iron(III) acetylacetonate in a mixture of solvents containing polyethyleneglycol (PEG) and branched polyethyleneimine (b-PEI) under vigorous stirring. Both PEG and b-PEI provided high water dispersibility by competitively surface coating the A-SPIONs. In addition, b-PEI controlled the overall morphology of the A-SPIONs, producing polyhedral nanocrystals in combination with the added halide ions. Due to the amine functional group from b-PEI, the A-SPIONs are proven to have both a positively charged surface (+29.1 mV) and active sites, which enable facile functionalization. Using A-SPIONs of 9.42 ± 2.93 nm (TEM observation), a high saturation magnetization value of 75.61 emu g⁻¹ was obtained using a superconducting quantum interface device (SQUID). The A-SPIONs sustained a stable dispersion in aqueous media with various pH, and their hydrodynamic size was about 13.97 nm in 0.10 M NaCl solution. Through the MTT assay, the A-SPIONs were proven 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), which originated from their high magnetization. Cyanine 5.5 dye-functionalized A-SPIONs (Cy 5.5@A-SPIONs) were prepared and serial experiments were conducted to investigate their fluorescence imaging applications. According to the results, the A-SPIONs are expected to have potential applications in bimodal imaging.