CTSB and cancer: The peptide Ad-CGKRK-GFLG-EE-HAIYPRH(T7) with a guest molecule Ad termination and cathepsin B (CTSB) (overexpressed in cancer cells)-cleavable linker GFLG was developed, and Ce6 was conjugated to the host molecule b-Cyclodextrin (b-CD) through an amide bond.