Preparation of aggregation-induced emission dots for long-term two-photon cell imaging†

Two-photon fluorescence imaging has attracted increasing interest in the biological and medical fields because of its low cell damage, high resolution, large imaging depth, and easy dynamic observation. A high-performance two-photon probe with long-term imaging capability was proposed for this imaging technology. In this work, a new two-photon probe compound was synthesized from tetraphenylethylene fluorogen with aggregation-induced emission. A phenyl-[phenyl-(1,2,5-thialdiazol)] amine group was induced to red-shift the absorption and emission wavelengths of the compound. After self-assembly, fluorescent dots with aggregation-induced emission cores and hydrophobic shells terminated by –COOH were formed. Cell experiments proved that the 4-(7-(phenyl(4-(1,2,2-triphenylvinyl)phenyl)amino)benzo[c][1,2,5]thiadiazol-4-yl)benzoic acid (TPECOOH) dots with red emission showed good biocompatibility and excellent two-photon imaging ability. TPECOOH dots were used successfully in direct long-term cell imaging with high efficiency. Even after twelve days, fluorescence imaging could still be observed in live HeLa cells.