Upon endocytosis of the nanoprobe to perform the therapy against cancer cells, the peptides are successively cleaved by intracellular caspase activation with the evolution from upstream to downstream, which lights up the fluorescence of the dyes sequentially, and can be used to quantify both caspase-9 and caspase-3 activities in cancer cells and to monitor their evolution in living mice. Here, CASP9 is linked to cancer.