On application of magnetic nanoclusters to improve the sensitivity of pulsed magnetomotive ultrasound imaging

Pulsed magneto-motive ultrasound (pMMUS) imaging of small superparamagnetic nanoparticles (NPs) has been introduced as a tool capable of imaging events at molecular and cellular levels in tissue. The sensitivity of pMMUS system depends on several parameters including size, geometry and magnetic properties of the NPs. Under the same magnetic field, larger magnetic nanostructures experience stronger magnetic force and thus produce larger pMMUS signal. Unfortunately, large magnetic iron-oxide NPs exhibit ferromagnetic properties such as spontaneous magnetization and coercivity and thus are difficult to stabilize against colloidal aggregation. In this study, we demonstrate enhanced pMMUS imaging by using large size clusters of superparamagnetic nanoparticles.