FeO assembly for tumor accurate diagnosis by endogenous GSH responsive / magnetic relaxation conversion.

Superparamagnetic iron oxide nanoparticles with high magnetization strength and good biological safety have been widely used as magnetic resonance imaging (MRI) contrast agents for tumors. However, the accuracy of tumor diagnosis is still low due to the lack of tumor targeting and the interference signals from normal tissues. Endogenous substances in tumor (such as high levels of GSH and pH) stimuli-responsive contrast agents could offer higher sensitivity for tumor diagnosis. Herein, based on the characteristic of overexpression of GSH in tumors, we propose an ultra-small FeO assembly as an endogenous GSH responsive MRI contrast agent. The ultra-small superparamagnetic FeO are bonded to the crosslinker cystamine to synthesize FeO nanoclusters, which exhibit a imaging effect. When the contrast agent reaches the tumor tissue, the disulfide bond in cystamine is induced by GSH to break, the FeO nanoclusters are disassembled into ultra-small FeO nanoparticles, and the relaxation signal changes from to , which is helpful for accurate diagnosis of tumors. experiments have shown that FeO nanoclusters can rapidly respond to overexpressed GSH in tumor sites for / switchable imaging. This work not only designed an endogenous GSH responsive platform through simple synthesis methods, but also improved the accuracy of tumor diagnosis through the transformation of / MRI signals.