Coumarin/BODIPY Hybridisation for Ratiometric Sensing of Intracellular Polarity Oscillation.

With different polarity responses, coumarin and 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) were hybridised to construct polarity fluorescent sensors, CBDP and iso-CBDP, to overcome the disadvantages of solvatochromic sensors in ratiometric polarity sensing. Only CBDP displayed an emission ratio (ICou /IBDP , coumarin to BODIPY emissions) that increased with an exponential dependence on medium relative permittivity over a wide polarity range (ϵr <57.9). This sensing ability of CBDP was not affected by medium pH; viscosity; and most intracellular species, especially reactive oxygen, nitrogen, and sulfur species. Apart from local cytoplasmic polarity quantification through lambda imaging, CBDP enables real-time ratiometric imaging for intracellular polarity oscillation induced by oxidative stimulation. Ratiometric polarity flow cytometry was developed, for the first time, with CBDP, which demonstrated that a high concentration H2 O2 induced cytoplasmic polarity enhancement, whereas pre-incubation with N-acetyl-l-cysteine inhibited this effect.