New fluorescent membrane probes: from naphthalenediimides to oligothiophenes

New fluorescent probes were introduced as an innovative methodology to label lipid bilayer membranes. This system is based on the dynamic covalent linkage between a hydrophilic charged head and a fluorescent tail. Dynamic amphiphiles formed from core-substitued naphthalenediimides (cNDIs) and perylenediimides (cPDIs) were tested first. These probes are insensitive to their environment and able to partition selectively into liquid-disordered (Ld) microdomains of mixed lipid bilayers and to activate DNA transporters. These results confirmed the potential of dynamic fluorescent amphiphiles to selectively label extra- and intracellular membranes. Oligothiophenes have been selected for the second generation of dynamic fluorescent amphiphiles. Lessons from nature suggest that the combination of fluorophore polarization (push-pull fluorophores) and fluorophore planarization could provide an attractive approach to achieve high sensitivity to membrane fluidity (microdomains), membrane potential and membrane stretching (and interesting NLO properties at interfaces). This combination was explored systematically by varying number and nature of substituents along the oligothiophene scaffold in combination with different donors and acceptors at both ends. The subsequent investigations in mixed lipid bilayers evidenced the ability of these new fluorophores to respond to membrane fluidity