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. Author manuscript; available in PMC: 2013 Oct 10.
Published in final edited form as: J Control Release. 2012 Jun 1;163(1):55–62. doi: 10.1016/j.jconrel.2012.05.044

Figure 1.

Figure 1

A) Schematic diagram of imaging the caspase cascade. Conventional dark-quenched, cell-impermeable fluorogenic probes for caspases can be efficiently delivered into the cells followed by simple incubation with a commercially available transfection agent such as PULSin® (Step 1). Once delivered into the cells, highly quenched probes are sequentially activated by expressed target caspases triggered by different initiator pathways, e.g. TRAIL-induced caspases activation (Step 2). B) Chemical structures of fluorogenic probes targeting caspase-8 and caspase-3, C8 and C3, respectively. Each probe consists of a substrate and a pair of dye/dark quencher with no significant spectral overlap of emission between the two probes.