DNA nanolantern-based split aptamer probes for in situ ATP imaging in living cells and lighting up mitochondria

Accurate and specific analysis of adenosine triphosphate (ATP) expression levels in living cells can provide valuable information for understanding cell metabolism, physiological activities and pathologic mechanisms. Herein, DNA nanolantern-based split aptamer nanoprobes are prepared and demonstrated to work well for in situ analysis of ATP expression in living cells. The nanoprobes, which carry multiple split aptamer units on the surface, are easily and inexpensively prepared by a "one-pot" assembly reaction of four short oligonucleotide strands. A series of characterization experiments verify that the nanoprobes have good monodispersity, strong biostability, high cell internalization efficiency, and fluorescence resonance energy transfer (FRET)-based ratiometric response to ATP in the concentration range covering the entire intracellular ATP expression level. By changing the intracellular ATP level via different treatments, the nanoprobes are demonstrated to show excellent performance in intracellular ATP expression analysis, giving a highly ATP concentration-dependent ratiometric fluorescence signal output. ATP-induced formation of large-sized DNA aggregates not only amplifies the FRET signal output, but also makes in situ ATP-imaging analysis in living cells possible. In situ responsive crosslinking of nanoprobes also makes them capable of lighting up the mitochondria of living cells. By simply changing the split aptamer sequence, the proposed DNA nanolantern-based split aptamer strategy might be easily extended to other targets.