Novel dual fluorescence temperature-sensitive chameleon DNA-templated silver nanocluster pair for intracellular thermometry

For the first time, we are reporting a novel type of dual fluorescence temperature-sensitive DNA-templated silver nanocluster (AgNC) pair, which contains two pieces of single-stranded AgNC in proximity through hybridization. Both the chameleon AgNC pairs, A-NCP and B-NCP, possess two bright fluorescence peaks that achieve sensitive variations corresponding to temperature change from 15 to 45 °C. With the increase in temperature, one of the fluorescence emissions of A-NCP (A-FL570) increases, while the other (A-FL640) decreases. However, both the emissions of B-NCP (B-FL685 and B-FL620) decrease simultaneously. Therefore, A-NCP shows a remarkable fluorescence color variation from orange to yellow, while the fluorescence color of B-NCP changes from orange to colorless, with increase in temperature. Moreover, the temperature responding linear range of A-NCP can be regulated by adjusting the structures and sequences of assistant DNA templates. It is assumed that the two single-stranded segmental AgNCs are integrated together as they are assembled into AgNC pairs, leading to a dramatic variation in fluorescence properties. The temperature-sensitive phenomenon is due to the dehybridization-induced separation of two pieces of segmental AgNC, caused by temperature increase. The temperature-sensitive AgNC pairs have been successful in indicating the temperature of living cells, showing the potential for a new application of silver nanocluster as a nanothermometer with adjustable response range, bringing novel insight into the regulatory mechanism of AgNC fluorescence variation.