FURIN and cancer: To solve this issue, IEISAP has been harnessed to increase the relaxation efficiency of traditional T1 CAs, such as Gd(III)-based CAs [68,69,70], and T2 CAs, such as superparamagnetic iron oxide (SPIO) nanoparticle-based CAs [71,72], for tumor imaging with the help of enzymes that are overexpressed in cancer cells, such as ALP [68,73], caspase 3/7 (Casp3/7) [70,71], MMP-2 [69], and furin [72].