Quadrupolar dyes for non-linear optical imaging of cardiac cells

Fluorescent potential-sensitive probes (voltage sensitive dyes) are widely used in mapping myocardial contraction. Most of the commercially available systems exploit two mechanisms: electrochromism or photoinduced electron transfer. Despite the great time resolution provided by these systems, they are affected by a low signal to noise ratio. Our project aims to overcome this problem by developing a non-linear optical method to study cardiomyocytes contraction with four-dimensional resolution (in space and time). We decided to use quadrupolar fluorescent molecules1 that can stain the phospholipidic bilayer of cardiac cells. These molecular sensors are based on a double mechanism: first, a variation in the potential of the cell should result in a different fluorescent response. Second, the cell contraction should lower the symmetry order, with the consequence that the resulting non-centrosymmetric system would be able to generate non-linear second order responses, such as second harmonic generation.2 In this poster presentation, we report the synthesis and spectroscopic properties of a selected library of quadrupolar dyes. They all contain a central fluorescent core, asymmetrically functionalized via a statistical Sonogashira coupling, with two electron-donating arms, one bearing a lipophilic and the other a polar end, to ensure a homogeneous orientation of the probe within the cell membrane.