Coordination-Driven Self-Assembly of Iron Oxide Nanoparticles for Tumor Microenvironment-Responsive Magnetic...

Accurate diagnosis of diseases located in deep tissues is always challenging. The "always-on" probe often leads to false-positive signals due to nonspecific interaction of nanoprobes. Thus, stimuli-responsive nanoprobes are highly desirable, which, however, require complicated surface modification so as to achieve trigger-induced signal changes. Here pH-triggered switchable magnetic resonance imaging (MRI) nanoprobes were constructed by coordination-driven self-assembly of monodispersed iron oxide nanoparticles (MIONPs) with simple amino acid derivatives, which displayed typical T₂-weighted MRI features, yet, were turned into T₁-weighted MRI under slightly acidic conditions at the tumor site. The dynamic assembly and disassembly properties of MIONPs afford T₂/T₁ switchable contrast imaging, enabling selective "turn-on" signals at the tumor site with high specificity.