The aptamer DNA-templated fluorescence silver nanoclusters: ATP detection and preliminary mechanism investigation

Two general and reliable fluorescence sensors were proposed in this work utilizing aptamer DNA-templated silver nanoclusters (Ag NCs). Both DNA-AgNCs could be used for label-free detecting of ATP with the limits of detection of 0.44 and 0.65 mM. One of them was further applied to monitor the activity of adenosine deaminase (ADA). In our effort to elucidate the light-up mechanism, we studied a total of six Ag NCs prepared by different DNA sequences, and found that they showed different sensitivity to ATP. Both BT3T3- and BT3T3(R)-templated Ag NCs were chose to make particular studies by UV–vis, TEM, fluorescence, and TCSPC methods. The results showed that when DNA-Ag NCs was kept for 1.5 h and presented a strong fluorescence, the addition of ATP failed to cause a large change of fluorescence intensity; on the contrary, after Ag NCs was kept for 24 h and emitted a weak fluorescence, adding ATP was able to result in the large fluorescence enhanced of 43 and 33 times for BT3T3- and BT3T3(R)-templated Ag NCs, respectively. The possible mechanism was also suggested that ATP binding to aptamer segment of template induced the change of the DNA secondary structure, which made the aggregated Ag nanoparticles disperse into Ag NCs with an average diameter of about 2 nm that were responsible for the large fluorescence increase. Moreover, ATP could protect the fluorescence intensity of BT3T3(R)-templated Ag NCs from quenching for at least 9 h.