Iron oxide nanoclusters formed by acid-induced in situ calcium ion cross-linking for targeted magnetic resonance imaging of glioblastoma

A “Dual-Key-and-Lock” MRI Contrast Agent with T1–T2 Switchable Function for Accurate Diagnosis of Tumors

“…Extremely small iron oxide nanoparticles (ESIONPs) are a T 1 -type CA with intriguing property, wherein they can switch to a T 2 -type one when aggregating due to magnetic coupling. − Obviously, utilizing the contrast enhancement transition between T 1 and T 2 of ESIONPs to design stimuli-responsive smart CAs can greatly enhance tumor specificity and reduce background signal . At present, various T 1 –T 2 and T 2 –T 1 switchable CAs have been developed for the diagnosis of brain diseases , and tumors. ,, For instance, Liu et al reported o-phenylenediamine and mannose-functionalized ESIONPs, which could assemble in response to the biomarker NO from the transition of M2 to M1 macrophages, offering insights into tumor macrophage M1/M2 polarization for precisely evaluating cancer prognosis . Moreover, previous work in our group utilized 4,4′-azodianiline as a cross-linker to obtain an ESIONP nanocluster (EAmP), which could respond to the tumor hypoxic microenvironment and decompose into dispersed ESIONPs, leading to a switch from T 2 to T 1 contrast enhancement for accurate tumor diagnosis .…”