DNA tetrahedron-based split aptamer probes for reliable imaging of ATP in living cells

Accurate detection and imaging of adenosine triphosphate (ATP) expression levels in living cells is of great value for understanding cell metabolism, physiological activities, and pathologic mechanisms. Here, we developed a DNA tetrahedron-based split aptamer probe (TD probe) for ratiometric fluorescence imaging of ATP in living cells. The TD probe is constructed by hybridizing two split ATP aptamer probes (Apt-a and Apt-b) to a DNA tetrahedron assembled by four DNA oligonucleotides (T1, T2, T3 and T4). In the presence of ATP, the TD probe will alter its structure from the open to closed state, thus bringing the separated donor and acceptor fluorophores into close proximity for high fluorescence resonance energy transfer (FRET) signals. The TD probe exhibits low cytotoxicity, efficient cell internalization and good biological stability. Moreover, based on the FRET "off" to "on" signal output mode, the TD probe can effectively avoid false-positive signals from complex biological matrices, which is significant for long-term reliable imaging in living cells. In addition, by changing the split aptamers attached to DNA tetrahedron, the proposed strategy may be extended for detecting various intracellular targets. Collectively, this strategy provides a valuable sensing platform for biomarkers analysis in living cells, thus having great potential for early clinical diagnosis and therapeutic evaluation.