Tiny nuance leads to large difference: Construction of fluorescent probes to visualize early and late apoptotic stages

Apoptosis is an exquisitely controlled complex process which plays key roles in maintaining cell homeostasis. Abnormal regulation of apoptosis was directly related to severe diseases including cancer, neurodegenerative diseases, and cardiovascular diseases. Herein, we proposed a chain-engineering strategy for constructing probes to distinguish the different stages of apoptosis. Two fluorescent probes (CPI-2 and CPI-3) with very similar structure were developed to detect the late and early apoptotic stages, respectively. CPI-2 with short chain could not enter live cells due to its poor membrane permeability, and thus exclusively illuminated the nucleolus of late apoptotic cells with damaged plasma membrane. CPI-3 was permeable to biomembranes and stained mitochondria in living cells, which immigrated into the nucleolus during early apoptotic procedure due to the decrease of mitochondrial membrane potential. Furthermore, CPI-2 and CPI-3 were successfully used to monitor the different stages of apoptosis induced by different concentrations of H2O2, paclitaxel, and rotenone. Particularly, we studied the heavy metals poisoning and detoxification of cysteine by CPI-2 and CPI-3. This work provides a viable strategy for constructing probes to detect the different stages of apoptosis, which is expected to promote the development of probes to monitor apoptosis processes. [Display omitted] •A chain-engineering strategy for probes to detect the early and late apoptosis was proposed.•Two probes with similar chemical structures were developed to distinguish different apoptotic stages.•CPI-2 was impermeable to intact biomembranes which enabled detection of late apoptosis.•CPI-3 exhibited good membrane permeability which could detect early apoptosis via subcellular immigration.•Both probes were used to study heavy metal poisoning and the detoxication of cysteine.