A dual-targeting fluorescent probe for simultaneous and discriminative visualization of lipid droplets and endoplasmic reticulum

A single fluorescent probe (SF-probe) that can simultaneously and discriminatively visualize two organelles is a powerful tool to investigate their interaction in cellular processes. However, it is still challenging to develop this unique type of fluorescent probe due to the lack of a feasible design strategy. Herein, we proposed a dual-targeting group strategy to construct SF-probes by integrating two different organelle-targeting groups into the same fluorophore. A versatile fluorophore and two nonintrusive organelle-targeting groups are elements of this strategy. In view of only a few SF-probes having been developed for the simultaneous and discriminative imaging of lipid droplets (LDs) and endoplasmic reticulum (ER), as a proof of concept, a SF-probe, LDER, was designed and synthesized by introducing an LD targeting group and an ER targeting group onto the 1,8-naphthalimide fluorophore. Owing to the specific structure of the fluorophore, both targeting groups at two terminals of 1,8-naphthalimide can fully play their respective roles without mutual interference. Furthermore, the ability of the two groups to target their respective targets is comparable, enabling LDER to bind LDs and ER evenly. Meanwhile, LDER is very susceptible to polarity, which is advantageous for the discriminative imaging of LDs and ER. In addition, the interaction between LDs and ER was investigated.