Unique pH-Sensitive RNA Binder for Ratiometric Visualization of Cell Apoptosis.

Fluorescent probes for monitoring cell apoptosis are powerful tools in biological and pathological research. However, ratiometric probes for in situ and real-time visualization of apoptosis with high accuracy are still deficient, which limits the studies relative to cell apoptosis. In this work, a pH-sensitive and positively charged RNA binder was designed and synthesized for the first time for the ratiometric visualization of cell apoptosis. In healthy cells, the probe targets mitochondria with basic matrixes and high membrane potential and displays intense emission in the blue and red channels. During apoptosis, the probe is released from mitochondria, binds to basophilic RNA, and shows emission in only the red channel. Consequently, cell apoptosis caused by drug treatment could be efficiently and clearly monitored in a ratiometric manner. The probe is expected to facilitate the study of cell apoptosis and relative areas.