Spectroscopic study on the formation of DNA-Ag clusters and its application in temperature sensitive vehicles of DOX.

DNA silver nanoclusters (DNA-AgNCs) with a fluorescence emission at 610 nm were synthesized using a special hairpin DNA sequence (5'-AGCACGTAG-C3AC3AC3GC3A-CTACGTGCT-3'). Spectroscopic data demonstrate that the DNA changed from an i-motif structure containing C-quadruplexes to anti-parallel four strands structure during the formation of DNA-AgNCs. Importantly, the loose and compact four strand structure caused by the melting and hybridization of stem duplex was confirmed by the reversible fluorescence change of DNA-AgNCs in the range of 25-66°C. Herein, DNA-AgNCs were used as temperature sensitive vehicles of drug loading. The drug loading capacity is 1 Doxorubicin (Dox) molecules per CG pairs on stem-duplexes. The loaded Dox can be released by raising temperature with the melt of stem duplex. Moreover, the special DNA sequence makes it sensitive to the HepG-2 cells.