Cationic molecular probes based on aggregation-induced emission for fluorescent sensing and super-resolution imaging of insulin fibrosis

[Display omitted] •The tetraarylethylenes with different aromatic ketone are synthesized by GCC reaction.•Hydrophilic tetraarylethylenes exhibit AIE effect opposite to their hydrophobic precursors.•The detection limit of cationic probes for insulin fibrils is as low as 0.64 nM.•Cationic tetraarylethylenes allow super-resolution imaging of fibrils via electrostatic interaction.•Super-resolution imaging of insulin fibrils with a high resolution of 35 nm. Amyloid fibrosis of protein is one of protein-related essential issues, which provides the critical information for the diagnosis and therapy of degenerative diseases. Insulin possesses the determined structure and relatively low molecular weight, which is often used as the main model protein to study amyloid fibrosis. Here, we have designed and synthesized three hydrophilic cationic aggregation-induced emission (AIE) probes with different aromatic ketone structures through geminal cross-coupling (GCC) reaction. Cationic AIE molecular probes can bind to insulin fibrils with negative charge at pH = 9.0 through electrostatic interaction, which constrains the intramolecular motion of probes and enhances the fluorescence. The detection limit of probes for insulin fibrils is as low as 0.64 nM. The random and sparse lighting of cationic molecular probes can be realized to enable the super-resolution imaging through the reversible electrostatic association-dissociation interaction between the negative insulin fibrils and positive molecular probes. The fine structure of the fibrils is observed, and full-width at half maximum (FWHM) for assessing the resolution can reach 35 nm, which is of great significance for the development of high-performance super-resolution imaging probes based on aggregation-induced emission and their optical nanoscale visualization applications in the exploration of amyloid fibrillation and related diseases.