ROS-Responsive T1/T2 Mode-Switchable MRI Contrast Agents for Tumor Diagnosis

To overcome the limitations of traditional contrast agents in terms of targeting and diagnostic sensitivity, we present superparamagnetic nanoclusters (Ncs) in combination with rationally designed nanocarriers for accurate tumor diagnosis. The Ncs were formed by monodisperse superparamagnetic manganese ferrite linked by thioketal bonds, which behave as T 2 contrast agents in normal tissues in vivo. The thioketal bonds within the Ncs break once they enter the tumor microenvironment response to its high reactive oxygen species (ROS) level, which achieves imaging mode flipping. The T 1 / T 2 switchable contrast greatly improves the MRI contrast of the disease, provides more information about the site of the lesion, and makes the diagnosis more accurate.