Microemulsion-Confined Assembly of Magnetic Nanoclusters for pH/H₂O₂ Dual-Responsive T₂–T₁ Switchable MRI

In this work, a T2–T1 switchable superparamagnetic iron oxide nanoprobe with a pH/H2O2 dual response was obtained using a microemulsion method. This novel method for the controllable assembly of small iron clusters followed by their independent modification was reported, which could not be prepared by common synthetic methods. The size of the assembled nanoprobe was uniform and controllable, with a stable T2 magnetic resonance imaging (MRI) signal under a single condition. When the nanoprobe was exposed to the tumor environment, the higher H+ and H2O2 concentrations at the tumor site could dissociate the nanoprobe and redisperse into small iron clusters. When this occurred, the T2 MRI signal was converted into a T1 MRI signal, achieving specific detection of tumors by a pH/H2O2 dual-response T2–T1 MRI.