Viscosity probes towards different organelles with red emission based on an identical hemicyanine structure

Abstract

A series of viscosity probes targeting different organelles were obtained using a single hemicyanine dye as the matrix structure. Specifically, probes 1a–d were obtained by introducing four amines (6-amino-2H-chromen-2-one, N-(2-aminoethyl)-4-methylbenzenesulfonamide, dodecan-1-amine and N,N diphenylbenzene-1,4-diamine) into the indole hemicyanine dye of the carboxylic acid with a D–π-A structure. Their maximum absorption wavelengths were in the range 570–586 nm and they had relatively large molar absorption coefficients, while their maximum emission wavelengths in the red light region were in the range 596–611 nm. Moreover, their fluorescence intensity in glycerol was 35–184 times higher than that in phosphate buffer solution (PBS). The lg(Fl) and lg η of probes 1a–d showed good linearity with high correlation coefficients according to the Förster–Hoffman equation. In addition, cell staining experiments demonstrated that 1a–c could target lysosomes, endoplasmic reticulum and mitochondria, respectively. They could also undergo viscosity-detectable changes in the corresponding organelles under the action of the corresponding ion carriers.