A series of novel dibenzothiophene-based two-photon fluorescent probes for cellular nucleus imaging

Abstract

In this study, a series of novel dibenzothiophene-based two-photon excited fluorescence (TPEF) probes with excellent nuclear staining ability were prepared and investigated. The one-photon photophysical properties indicated these labels possessed UV absorption wavelength of 390–393nm and quantum yields of 0.425–0.71. The two-photon photophysical performance exhibited two-photon absorption (TPA) cross-sections of 506–630GM by excitation of femtosecond laser at a wavelength of 800nm. 18–30-fold one-photon excited fluorescence (OPEF) enhancement and 300–450% TPEF increment binding with calf thymus DNA in Tris-HCl buffer solutions displayed obvious fluorescence “turn-on” effect. The co-localization studies showed mean co-localization coefficients of 0.88–0.94 by double-staining with commercial nuclear staining reagent DAPI in 3T3 cells, indicating accurate nuclear localization ability. The confocal fluorescence imaging displayed clear TPEF nuclear imaging. The staining penetration depth of 0–9μm exhibited good membrane permeability and three dimensional imaging ability. The observation time of 1800s and fluorescence decay amplitude of 8–10% within 300s under persistent irradiation were achieved in TPEF imaging for nuclear labeling. The DNA binding mechanism was discussed as well.