Multi-DNA-Ag nanoclusters: reassembly mechanism and sensing the change of HIF in cells

A new type of fluorescent silver nanoclusters consisting of one silver bound to several strands of DNA, called multi-DNA-AgNCs, have been constructed using a bifunctional oligonucleotide with the recognition sequence 5'-CTACGTGCT-3' as a stabilizing agent. The target oligonucleotide causes the multi-DNA-AgNCs to reassemble into smaller sized Ag clusters with quenched emission properties, while BSA induces the reassembly of the multi-DNA-AgNCs to give large particles with an enhanced emission. This demonstrates that the multi-DNA-AgNCs can specifically detect this recognition sequence. Furthermore, the multi-DNA-AgNCs show different fluorescence responses toward the total protein of normal cells (WRL-68), HepG-2 cells and HepG-2 cells incubated with 5-fluorourcil (5-Fu). The results show that the total protein of the HepG-2 cells, in which HIF is highly expressed, significantly decreases the fluorescence emission. Consequently, the multi-DNA-AgNCs can be used as a fluorescence probe for the detection of cancer cells, which have a high expression of HIF.