In present study, we synthesized a targeting nanoprobe for nucleolin highly expressed cancer cells labelling based on CDs which have been successfully prepared in previous experiments with favourable biocompatibility and fluorescence properties.34 As the bridge between CDs and the aptamer AS1411, PEI showed good biocompatibility in both L929 and MCF‐7 cells, while, the nanosystem exhibited enhanced cytotoxicity in MCF‐7 cells after loading AS1411. This evidence concerns the gene NUCLEOLIN and cancer.