Probing Cell Membrane Tension Using DNA Framework-Encoded Vibration-Induced Emission Molecular Assemblies

Mechanosensitive fluorescent probes are valuable tools for detecting changes in cellular mechanics and viscosity. While numerous mechanosensitive probes have been developed, the construction of molecular assemblies for probing cellular mechanics remains largely unexplored, possibly due to the challenges of designing assemblies with synergistic and integrated functionalities. Here, we report the design and synthesis of mechanosensitive molecular assemblies by integrating DNA frameworks with vibration-induced emission (VIE) probes to enable live-cell membrane tension imaging. The molecular assemblies consist of a rigid tetrahedral DNA framework anchored with prescribed numbers of VIE probes. We find that VIE probes on the DNA framework retain their ratiometric fluorescence response characteristics in aqueous systems and on lipidic model membranes. Importantly, VIE assemblies exhibit distinct cell membrane targeting behaviors depending on the number of contact points between the molecular assemblies and the cell membrane. Especially, trivalent molecular assemblies can inhibit the internalization of the probes by the cells, a property absent in free VIE and mono/divalent molecular assemblies, thereby achieving targeted and prolonged retention on the cell membrane. Using the trivalent molecular assemblies, we successfully achieve ratiometric fluorescence imaging of cell membrane tension using confocal laser scanning microscopy, revealing the potential of such multifunctional mechanical-sensitive probes for live-cell applications.