Synthesis of highly selective lysosomal markers by coupling 2-(2'-hydroxyphenyl)benzothiazole (HBT) with benzothiazolium cyanine (Cy): the impact of substituents on selectivity and optical properties

J Mater Chem B. 2019 Dec 21;7(47):7502-7514. doi: 10.1039/c9tb01672d. Epub 2019 Nov 12.

Abstract

HBT-Cy 1 has been previously reported as a highly selective fluorescent probe for lysosome visualization in live cells. To further investigate the role of the structural components of HBT-Cy in lysosome selectivity, cyanine based fluorescent probe series (2-5) have been synthesized in good yields by connecting benzothiazolium cyanine (Cy) with 2-hydroxyphenylbenzothiazole (HBT) via a meta phenylene ring. Probes 2-5 exhibited exceptional photophysical properties including bright red-emission (λem≈ 630-650 nm), a large Stokes shift (Δλ > 130 nm) and high fluorescence quantum yields (φfl≈ 0.1-0.5). Probes 2, 3, and 5 exhibited exceptional selectivity towards cellular lysosomes in NHLF and MO3.13 cells. Our further study revealed that the phenyl benzothiazolium cyanine component (6) was the lysosome directing group in the HBT-Cy probe structure. The attachment of the hydroxyphenyl benzothiazole (HBT) component to the HBT-Cy probe structure has significantly improved its photophysical properties. Lysosome probes 2, 3 and 5 exhibited excellent biocompatibility, quick staining, bright red fluorescence, and wash-free application for live cell imaging. These probes further exhibited excellent characteristics for bioimaging experiments including a non-alkalinizing nature, high biocompatibility, high photostability and long-term imaging ability (>4 hours).

MeSH terms

  • Benzothiazoles / chemistry*
  • Biocompatible Materials / chemistry
  • Biocompatible Materials / pharmacology
  • Carbocyanines / chemistry*
  • Cell Line
  • Cell Survival / drug effects
  • Fluorescent Dyes / chemistry*
  • Fluorescent Dyes / pharmacology
  • Humans
  • Hydrogen-Ion Concentration
  • Lysosomes / chemistry*
  • Microscopy, Confocal
  • Phenols / chemistry*
  • Temperature

Substances

  • Benzothiazoles
  • Biocompatible Materials
  • Carbocyanines
  • Fluorescent Dyes
  • Phenols
  • 2-(2-hydroxyphenyl)benzothiazole
  • benzothiazole