摘要：Two interesting benzothizolium-based D-π-A type hemicyanine dyes (
3a–
3b) with a diphenylamine (-NPh
2) donor group were evaluated for fluorescence confocal microscopy imaging ability in live cells (MO3.13, NHLF). In sharp contrast to previously reported D-π-A dyes with alkyl amine donor (-NR
2) groups (
1),
3a and
3b exhibited significantly different photophysical properties and organelle selectivity. Probes
3a and
3b were nearly non-fluorescent in many polar and non-polar solvents but exhibited a bright red fluorescence (λ
em ≈ 630–640 nm) in stained MO3.13 and NHLF with very low probe concentrations (i.e., 200 nM). Fluorescence confocal microscopy-based co-localization studies revealed excellent lysosome selectivity from the probes
3a–
3b, which is in sharp contrast to previously reported D-π-A type benzothiazolium dyes (
1) with an alkyl amine donor group (-NR
2) (exhibiting selectivity towards cellular mitochondria). The photostability of probe
3 was found to be dependent on the substituent (R’) attached to the quaternary nitrogen atom in the cyanine dye structure. The observed donor-dependent selectivity switching phenomenon can be highly useful in designing novel organelle-targeted fluorescent probes for live-cell imaging applications.
