“…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 . Nevertheless, all these T 1 –T 2 and T 2 –T 1 switchable CAs generally respond to a single biomarker stimulus, such as pH, glutathione (GSH), hypoxia, enzyme, and so forth.…”