Flipper dendrimers

Abstract

Fluorescent flippers have been introduced as small-molecule probes to image physical forces within cell membranes. Despite their popularity and much effort, significant improvements of performance have not been reported since their first design. Now, almost a decade after their introduction, we disclose flipper dendrimers that address the main practical problem with flipper probes: phototoxicity. Flipper dendrimers provide much stronger fluorescence in cells while maintaining responsiveness to changes in membrane tension. This increased effective brightness enables imaging at almost one order of magnitude lower laser power to generate the same fluorescence intensity, thereby reducing phototoxicity and allowing longer monitoring of biological processes. This breakthrough is achieved using large peptide dendrimers that maximize deliverability as Israelachvili-inspired inverted cones. Peptide dendrimers and hydrophobic interfacers modulate fluorescence lifetime and plasma membrane targeting by controlling probe orientation, interdomain distribution, intermembrane transfer and internalization. This supramolecular chemistry strategy to improve performance by engineering probe integration into the environment, rather than the mechanophore itself, is generally applicable.