Immobilization of iron oxide nanoparticles within alginate nanogels for enhanced MR imaging applications

Abstract

We report the design of iron oxide (Fe₃O₄) nanoparticle (NP)-immobilized alginate (AG) nanogels (NGs) as a novel contrast agent for enhanced magnetic resonance (MR) imaging applications. In this study, an aqueous solution of AG activated by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride was double emulsified to form NGs, followed by in situ cross-linking with polyethyleneimine (PEI)-coated Fe₃O₄ NPs (PEI-Fe₃O₄ NPs). The resultant Fe₃O₄ NP-immobilized AG NGs (AG/PEI-Fe₃O₄ NGs) were characterized via different techniques. Our results reveal that the hybrid NGs with a size of 186.1 ± 33.1 nm are water dispersible, colloidally stable, and cytocompatible in the given concentration range. Importantly, these NGs have a high r₂ relaxivity (170.87 mM⁻¹ s⁻¹) due to the high loading of Fe₃O₄ NPs within the NGs, and can be more significantly uptaken by cancer cells when compared with carboxylated Fe₃O₄ NPs. The formed AG/PEI-Fe₃O₄ NGs are able to be used as an effective contrast agent for the MR imaging of cancer cells in vitro and the xenografted tumor model in vivo after intravenous injection. The developed AG/PEI-Fe₃O₄ NGs may hold great promise for use as a novel contrast agent for the enhanced MR imaging of different biological systems.