Highly sensitive cell imaging "Off-On" fluorescent probe for mitochondria and ATP.

A smart Off-On molecular scaffold/fluorescent probe 1 has been designed and synthesized. The probe has shown considerable photostability, cell permeability, organelle specificity and selectivity for ATP. The multicolor live cell imaging experiments in HeLa cells showed high selectivity of probe 1 for mitochondria with fluorescence "turn-on" response. As a proof of concept and promising prospects for application in biological sciences probe 1 has been utilized to detect ATP sensitively in a partial aqueous medium and intracellularly in HeLa cells. The favorable interaction between triphosphate unit of ATP and piperazine N atoms of probe 1 is attributed to synergistic effects of H-bonding and electrostatic interactions that encouraged the CH-π and π→π stacking between anthracene and purine rings. Consequently, the observed enhanced "turn-on" emission and a naked-eye sensitive blue-green color in the medium is attributable to arrest in photoinduced electron transfer (PET) process.