Synthesis of superparamagnetic iron oxide nanoparticles coated with a DDNP-carboxyl derivative for in vitro magnetic resonance imaging of Alzheimer's disease

•SPIONs are coated with the novel compounds DDNP-carboxyl derivative.•We described a facile chemical method to functionalize the surface of SPIONs.•They show superparamagnetic and high relaxivity.

Superparamagnetic iron oxide nanoparticles (SPIONs) have been proposed for use in magnetic resonance imaging as versatile ultra-sensitive nanoprobes for Alzheimer's disease imaging. In this work, we synthetized an efficient contrast agent of Alzheimer's disease using 1,1-dicyano-2-[6-(dimethylamino)naphthalene-2-yl]propene (DDNP) carboxyl derivative to functionalize the surface of SPIONs. The DDNP-SPIONs are prepared by conjugating DDNP carboxyl derivative to oleic acid-treated SPIONs through ligand exchange. The structure, size distribution and magnetic property were identified by IR, TGA–DTA, XRD, TEM, Zetasizer Nano and VSM. TEM and Zetasizer Nano observations indicated that the DDNP-SPIONs are relatively mono-dispersed spherical distribution with an average size of 11.7 nm. The DDNP-SPIONs were then further analyzed for their MRI relaxation properties using MR imaging and demonstrated high T2 relaxivity of 140.57 s− 1Fe mM− 1, and the vitro experiment that DDNP-SPIONs binding to β-Amyloid aggregates were then investigated by fluorophotometry, the results showed that the combination had induced the fluorescence enhancement of the DDNP-SPIONs and displayed tremendous promise for use as a contrast agent of Alzheimer's disease in MRI.