Novel and efficient MR active aqueous colloidal Fe₃O₄ nanoassemblies

This work demonstrates a new class of magnetic resonance (MR) active aqueous Fe₃O₄ magnetic nanoparticle nanoassemblies (Fe₃O₄ MNNA) of ∼40 nm size comprising ∼6 nm particles. They exhibit enhancement in T₂ MR contrast as compared to 6 nm isolated counterparts (Fe₃O₄ MNP) and commercial contrast agent, ferumoxytol. This significant improvement in the T₂ MR signal arises from the synergistic magnetism of multiple Fe₃O ₄ nanoparticles assembled in Fe₃O₄ MNNA. These nanoassemblies also show better colloidal stability, higher magnetization, good specific absorption rate (under external AC magnetic field) and cytocompatibility with cells. Further, the functional groups (-NH₂) present on the surface of Fe₃O₄ particles can be accessible for routine conjugation of biomolecules through well-developed bioconjugation chemistry. Specifically, a new MR active colloidal amine-functionalized Fe₃O₄ nanoassembly with enhanced T₂ contrast properties has been fabricated, which can also be used as an effective heating source for hyperthermia treatment of cancer.