One-pot biofunctionalization of magnetic nanoparticles via thiol-ene click reaction for magnetic hyperthermia and magnetic resonance imaging

Cysteine-modified Fe₃O₄ nanoparticles (Cys-Fe ₃O₄ NPs) were synthesized by the one-pot biofunctionalization of allyl-functionalized Fe₃O₄ NPs (allyl-Fe₃O₄) with cysteine using the in situ hydrolysis-condensation of iron(III) allylacetylacetonate and the thiol-ene click reaction. The particle size of Fe₃O₄ in Cys-Fe ₃O₄ NPs measured by transmission electron microscopy and X-ray diffraction analysis was ∼8 nm. Cys-Fe₃O₄ NPs were soluble in water and had a hydrodynamic diameter of 22 nm and prolonged stability in water. They were superparamagnetic, which was confirmed by fitting the Langevin equation to the magnetization data, generated heat in an alternating current (AC) magnetic field, and had a specific absorption rate (SAR) of 156 W g^-1 at 230 kHz and 100 Oe. In addition, they exhibited a T₂-weighted magnetic resonance imaging (MRI) contrast-enhancing effect.