Golgi polarity fluorescent imaging based on coumarin or 1,8-naphthalimide derivatives in three channels

As a key parameter affecting the biochemical reaction of cells, the change of polarity also affects some important biological processes of cells. However, there are very few polarity probes for Golgi apparatus. In this work, coumarin or 1,8-naphthalimide were chosen as the fluorophores for their excellent optical property. Based on the combination of amide and long carbon chain, three Golgi polarity probes with different emission regions were designed and synthesized. Among them, Golgi-Blue and Golgi-Green inherited the blue and green fluorescence of the parents, respectively; while after the introduction of dicyanoisophorone unit to the 1,8-naphthalimide, Golgi-Red achieved near infrared emission (700–750 nm). Moreover, the three probes were sensitive to the polarity of solution. Interestingly, the fluorescence of Golgi-Blue and Golgi-Green decreased whereas that of Golgi-Red first enhanced gradually and then weakened with the increase of polarity, which was caused by the configuration change of the ground and excited state to induce twisted intramolecular charge transfer (TICT) in 1,4-dioxane and elucidated by means of density functional theory. Cell experiments showed that the three probes could quickly and accurately target Golgi apparatus and monitor the changes of Golgi polarity. The results may help in the early diagnosis of polar-related diseases.