Xu et al. developed a multi-color fluorescent polydopamine nanobiosensor for the multiple sensing of cancer-related proteases in living cells, such as urokinase-type plasminogen activator (uPA), cathepsin B (CTB), matrix metalloproteinase-2, and matrix metalloproteinase-7 (MMP-7) [92]. The gene discussed is MMP2; the disease is cancer.