For example, the use of another peptide sequence48, 49, NH2–GGRRGGC–SH instead of H2N–GPLGVRGC–SH, as the linker between Acy and AuNRs enables the fabrication of a nanoprobe (Pep2-Acy@AuNRs) for specific response to cathepsin B (CtsB), a tumour-specific enzyme overexpressed in various malignant tumours25, 48, 49, and the specific fluorescence activation of Pep2-Acy@AuNRs synergistically governed by CtsB and pH (Supplementary Figs 19–23). This evidence concerns the gene CTSB and neoplasm.