Rhodamine derivatives bearing thiourea groups serve as fluorescent probes for selective detection of ATP in mitochondria and lysosomes

ATP functions as an energy source in all living things and it also plays key roles in a variety of important biological processes. Moreover, low levels of ATP are indicators of cardiovascular disease, Parkinson's disease and ischemia. As a result, the development of fluorescent probes that detect ATP selectively is a significant goal. In the current study, we synthesized two new rhodamine derivatives, 1 and 2, bearing thiourea groups, and assessed their abilities to serve as selective fluorescent and colorimetric probes for ATP. Thiourea groups were incorporated in 1 and 2 to act as hydrogen bonding donors to recognize tris-phosphate groups and induce photophysical property changing, spirocyclic ring opening. Indeed, we observed that solutions of these probes undergo a large fluorescent enhancement at 590 nm and a distinct colorimetric change from colorless to dark pink upon addition of ATP. Moreover, these probes can be used to image ATP in HeLa cells. Because it was found to locate mainly in mitochondria, 2 can be employed to image ATP in mitochondria. On the other hand, probe 1, bearing a lysosome directing morpholine group displays moderately selective localization in lysosomes and can be utilized to image ATP in lysosomes. Furthermore, both probes were shown to have extremely low cytotoxicities by using MTT assays.