Bioconjugation of a Near-Infrared DNA-Stabilized Silver Nanocluster to Peptides and Human Insulin by Copper-Free Click Chemistry

DNA-stabilized silver nanoclusters (DNA-AgNCs) are biocompatibleemitters with intriguing properties. However, they have not been extensivelyused for bioimaging applications due to the lack of structural informationand hence predictable conjugation strategies. Here, a copper-freeclick chemistry method for linking a well-characterized DNA-AgNC tomolecules of interest is presented. Three different peptides and asmall protein, human insulin, were tested as labeling targets. Theconjugation to the target compounds was verified by MS, HPLC, andtime-resolved anisotropy measurements. Moreover, the spectroscopicproperties of DNA-AgNCs were found to be unaffected by the linkingreactions. For DNA-AgNC-conjugated human insulin, fluorescence imagingstudies were performed on Chinese hamster ovary (CHO) cells overexpressing human insulin receptor B (hIR-B). The specific staining of the CHOcell membranes demonstrates that DNA-AgNCs are great candidates forbioimaging applications, and the proposed linking strategy is easyto implement when the DNA-AgNC structure is known.