In another study, Shi et al. [82] constructed a hairpin-structured activatable aptamer probe (AAP) consisting of a specific sgc8 aptamer (A-strand), a poly-T linker (T-strand), and a short DNA sequence (C-strand) with a fluorophore and a quencher in order to detect the cell membrane protein tyrosine kinase-7 (PTK7) for human acute lymphoblastic leukemia CCRF-CEM cells. Here, PTK7 is linked to acute lymphoblastic leukemia.