Development of 1,3a,6a-triazapentalene derivatives as practical erasable fluorescent cell staining reagents

Abstract

1,3a,6a-Triazapentalene (TAP) derivatives were developed as erasable fluorescent cell staining reagents that can be used with a confocal laser microscope. To enhance the utility of previously developed erasable fluorescent cell staining reagents such as 2-biphenyl-TAP (1a) for practical applications in confocal laser microscopy, a carbonyl group with strong electron-withdrawing properties was introduced between the TAP core skeleton and the biphenyl group, leading to a longer wavelength shift in absorption and emission maxima. While the analog 1b, featuring only the carbonyl group insertion, declined significantly in fluorescence intensity, the two-carbon extended ketone analog 1d showed a desirable shift in absorption maximum towards longer wavelengths, green fluorescence, and high fluorescence intensity. Cell staining experiments using 1d demonstrated its usefulness, including rapid staining, erasable fluorescent staining, and compatibility with confocal laser microscopy employing a standard filter.