MMP2 and neoplasm: To address this issue, Yin et al. developed a novel matrix metalloproteinase-2 (MMP-2)-activatable probe constructed with a near-infrared dye (Cy5), a quencher (QSY21), and a tumor-targeting peptide cRGD covalently linked through a radionuclide (125I)-labeled peptide substrate for accurate detection of MLNs [81].